Genetics Ch. 1

Mendel's mutant alleles

-dwarf plants -white flowers -terminal flowers -green seeds -wrinkled seeds -yellow pods -constricted pods

Mendel's wild type alleles

-tall plants -purple flowers -axial flowers -yellow seeds -round seeds -green pods -smooth pods

plant fertilization

1) a pollen grain (containing male gametes-sperm, and recall that pollen grains are formed in the anthers of the plant), lands on the stigma of. a plant the pollen grain containing the sperm landing on the stigma of a plant stimulates the growth of a pollen tube so due to the pollen grain containing the sperm landing on the stigma of a plant, the growth of a pollen tube occurs 2) the sperm cells contained within the pollen grain are able to enter the stigma and migrate towards an ovule which contains the female gametes-the eggs 3) a sperm cells enter the micropyle (THE MICROPYLE IS AN OPENING IN THE OVULE WALL, RECALL THAT THE OVULE CONTAINS ALL OF THE EGGS) 4) the sperm cell (haploid) fuses with the egg cell (haploid) in order to form a diploid zygote

cystic fibrosis

3 percent of the caucasian population are heterozygous carriers of this recessive allele so the heterozygotes with one copy of this recessive allele are not affected by its presence, but are carriers with homozygotes, the disease symptoms of cystic fibrosis that they experience include abnormalities of the: -pancreas -intestine -sweat glands -lungs these abnormalities are caused by the imbalance of ions across the plasma membrane of the cells of these organs within the lungs, due to the imbalance of ions across the plasma membranes of the lung cells, there is a buildup of thick, sticky mucus that causes numerous respiratory problems these aforementioned respiratory issues may lead to early death modern treatments for these respiratory issues have greatly increased the lifespan of CF patients the gene for CF was identified in the late 1980s this gene encodes a protein called the CYSTIC FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR (CFTR for short) the above protein regulates the ion balance across the cell membrane in the tissues of the: -pancreas -intestine -sweat glands -lungs there is a mutant allele that causes CF which alters the encoded CFTR protein the Cystic Fibrosis Transmembrane Conductance Regulator due to this alteration by the mutant allele, the cystic fibrosis transmembrane conductance regulator is not correctly inserted into the plasma membrane of these cells so this protein has decreased functionality that makes for an ionic imbalance the pattern of cystic fibrosis shown in the pedigree analysis is consistent with a recessive mode of inheritance two unaffected individuals if they both are carriers of the mutated allele, can produce an offspring that is homozygous recessive and has CF a note to make about a recessive mode of inheritance and a pedigree analysis this recessive mode of inheritance is characterized by the observation that two affected individuals (who would have homozygous recessive allelic combinations) will only be able to produce affected offspring another note is that with human genetic diseases that limit survival and/or fertility, there may never be a situation in which two affected individuals are able to procreate

chromosomal deletions

A CHROMOSOMAL DELETION a chromosomal deletion is a mutation that occurs WHEN A CHROMOSOME BREAKS IN ONE OR MORE PLACES in a chromosomal deletion, a chromosome breaks in one or more places in a chromosomal deletion, a chromosome breaks in one or more places after this chromosome breaks in one or more places in a chromosomal deletion, A FRAGMENT OF THE CHROMOSOME IS LOST a fragment of the chromosome, a chromosomal segment is lost in a chromosomal deletion in a chromosomal deletion, a chromosome breaks in one or more places, and a chromosomal segment/fragment is lost from the chromosome, resulting in a substantial and discernible loss of genetic material occurring in one chromosome in the displayed figure showcasing a chromosome deletion: A NORMAL CHROMOSOME HAS BROKEN INTO TWO SEPARATE PIECE there is a chromosomal deletion displayed in this figure, where a chromosome is broken into two individual segments the chromosomal segment without the centromere is lost and degraded, this chromosomal segment that ends up without the centromere when the original chromosomes breaks into two segments is lost and degraded THIS IS DESIGNATED AS A TERMINAL DELETION TERMINAL DELETION- this is a deletion where there is a huge segment of the chromosome permanently deleted, lost and degraded in this scenario, a chromosome is broken into two separate, individual segments, and the segment that does not contain the centromere is lost and degraded completely, so one of the two chromosomal segments is degraded and lost completely there is another example of a deletion shown in the figure: this is where a chromosome is BROEKN IN TWO PLACES a chromosome is broken in two places, and this creates 3 chromosomal segments THE CENTRAL FRAGMENT, the central segment of the chromosome, the central fragment of the 3 individual segments is lost and degraded, and the two other segments, the two outer chromosomal segments join with one another, they reattach to one another now that the middle segment of the 3 individuals segment has degraded and been lost this PROCESS HAS CREATED A CHROMOSOME WITH AN INTERSTITIAL DELETION an interstitial deletion is a deletion in a chromosome where there are 2 breaks in a chromosome, resulting in 3 individual segments out of the original chromosome the middle segment of the 3 individual segments is degraded and lost the two outer segments, the two remaining outer individual segments of the original chromosome reattach to one another, recreating a chromosome, creating a new chromosome with an interstitial deletion, where it is essentially the same original chromosome, missing the middle segment and containing only the genetic material of the outer segments that are now joined together another type of deletion: DELETIONS CAN ALSO BE CREATED WHEN RECOMBINATION TAKES PLACE AT INCORRECT LOCATIONS BW THE TWO HOMOLOGOUS CHROMOSOMES FORMING A SYNAPSE deletions can occur during meiosis, when genetic recombination amidst homologous chromosomes occurs, if recombination takes place at the incorrect locations bw homologous chromosomes THE PRODUCT OF THIS TYPE OF ABERRANT RECOMBINATION EVENT ARE ONE CHROMOSOME WITH A DELETION AND ONE CHROMOSOME WITH A DUPLICATION in improper genetic recombination, within the pair of homologous chromosomes that formed a synapse and underwent recombination, due to recombination taking place at incorrect locations on the homologous chromosomes, one chromosome has a deletion while the other has a duplication WHAT ARE THE PHENOTYPIC CONSEQUENCES OF A CHROMOSOMAL DELETION how does a chromosomal deletion affect the phenotype of an organism how is the phenotype of an organism affected by a chromosomal deletion what are the phenotypic consequences of a chromosomal deletion? the phenotypic consequences of a chromosomal deletion DEPEND ON THE SIZE OF THE CHROMOSOMAL DELETION AS WELL AS WHETHER OR NOT THE CHROMOSOMAL SEGMENT THAT WAS DELETED INCLUDES GENES OR PORTIONS OF GENES THAT ARE VITAL TO THE DEVELOPMENT OF THE ORGANISM the phenotypic consequences of chromosomal deletion depend upon the size of the chromosome (how many genes the chromosome carries, perhaps in a larger chromosome the deletion may not be as disastrous, but in smaller chromosome with fewer genes, a deletion will be substantial and impactful as a large amount of genetic material constituting the small chromosome will be lost) as well as the presence of vital genes or portions of vital genes in the deleted chromosomal segment, vital genes or portions of vital genes that are responsible for the proper development and survival of an organism (an organism may not develop if a chromosomal deletion results in the deletion of genes vital to its development and survival) WHEN DELETIONS DO HAVE. A PHENOTYPIC EFFECT when deletions do have a phenotypic effect, when deletions affect the phenotype of an organism, they are usually detrimental to the organism LARGER DELETIONS TEND TO BE MORE HARMFUL bc the larger the chromosomal segment that is deleted, the more genes that are probably deleted what deletions have SIGNIFICANT PHENOTYPIC INFLUENCES what chromosomal deletions have significant influence upon the phenotype of an organism? THERE IS A HUMAN GENETIC DISEASE this human genetic disease is designated as CRI-DU-CHAT, and this human genetic disease is caused by a chromosomal deletion this human genetic disease is designated as cri-du-chat, or Lejeune syndrome this human genetic disease cri-du-chat/lejeune syndrome in caused by A DELETION IN A SEGMENT OF THE SHORT ARM OF HUMAN CHROMOSOME 5 this human genetic disease cri-du-chat/lejeune SYNDROME IS CAUSED BY A DELETION IN A SEGMENT OF THE SHORT ARM OF HUMAN CHROMOSOME 5 there is a deletion in the short p arm of human chromosome 5 that causes cri-du-chat/Lejeune syndrome individual who carry a single copy of this abnormal chromosome 5, with a deletion of the short p arm, as well as a normal copy of chromosome 5, will have and display cri-du-chat/lejeune syndrome THEY WILL DISPLAY AN ARRAY OF ABNORMALITIES due to the presence of one abnormal copy of chromosome 5 in the pair of chromosome 5, the abnormal copy with a deletion of the short arm, the p arm INDIVIDUALS W THIS ONE ABNORMAL COPY OF CHROMOSOME 5 containing a deletion of the short arm, a deletion of the p arm WILL DISPLAY A MULTITUDE OF ABNORMALITIES this multitude of abnormalities includes: MENTAL DEFICIENCES UNIQUE FACIAL ANOMALIES AN UNUSUAL CATLIKE CRY IN INFANCY this unusual and identifiable catlike cry in infancy is the meaning of the French name of this syndrome cri-du-chat= cry of the cat, this syndrome is given this French name bc one of the abnormalities of this syndrome besides mental deficiencies and unique facial anomalies is the unusual sound of. a crying cat that individuals with this syndrome display in infancy individuals with this syndrome will make an unusual catlike cry in infancy, which is why the French name for this disease is cri-du-chat ANGELMAN AND PRADER WILLI SYNDROME ANGELMAN AND PRADER WILLI SYNDROME ARE DUE TO A DELETION IN CHROMOSOME 15 review ANGELMAN AND PRADER WILLI SYNDROME

viral genome

A VIRAL GENOME IS THE ENTITY OF THE GENETIC MATERIAL THAT A VIRUS CONTAINS a viral genome is the entity of the genetic material that a virus contains viral chromosome is another term utilized in order to describe the viral genome viral chromosome is another term utilized in order to designate the viral genome, the entity of genetic material that a virus contains can be referred to as the viral genome or the viral chromosome the nucleic acid composition of viral genomes, of the entities of genetic material of viruses, changes across the type of virus you are looking at the nucleic acid composition of viral genomes changes as you go from virus to virus, it differs among various types of viruses EXAMPLES OF HOW THE NUCLEIC ACID COMPOSITION OF VIRAL GENOMES CHANGES AS YOU MOVE FROM VIRUS TO VIRUS within the virus PARVOVIRUS, the host of the parvovirus is a mammal (all mammals can be hosts of the parvovirus), and the type of nucleic acid composing the genome of the parvovirus is ssDNA, SINGLE STRANDED DNA the size of the parvovirus genome is 5 thousand nucleotides or nucleotide base pairs, and there are 5 genes total found within the genome of the parvovirus within the virus Fd, the virus Fd, the host of this virus is E coli, the type of nucleic acid composing the genome of the virus Fd is ssDNA SINGLE STRANDED DNA the size of the Fd genome is 6,400 nucleotides or nucleotide base pairs the number of genes within the Fd genome is 10 within the virus lambda, the host of the virus lambda is e coli, the type of nucleic acid composing the genome of the virus lambda is dsDNA, DOUBLE STRANDED DNA the size of the virus lambda genome is 48,500 nucleotides or nucleotide base pairs the number of genes within the genome of the virus lambda is 71 within the T4 virus, the host of the T4 virus is E coli the type of nucleic acid composing the genome the entity of genetic material of the T4 virus is dsDNA DOUBLE STRANDED DNA the size of the T4 virus genome is 169,000 nucleotides or nucleotide base pairs the number of genes found within the T4 virus genome is 288 genes within the QB the Beta virus, the host for the QB virus is E coli the type of nucleic acid that composes the genome of the QB virus is ssRNA SINGLE STRANDED RNA the size of the genome of the QB virus is 4.2 nucleotides or nucleotide base pairs the number of genes in the genome of the QB virus is 4 genes total within the TMV virus, the host for the TMV virus includes many plants the type of nucleic acid that composes the genome of TMV is ssRNA SINGULAR STRAND RNA the size of the genome of TMZ is 6.4 nucleotides or nucleotide base pairs the number of genes found within the genome of the TMV virus is 6 genes within the influenza virus, the host for the influenza virus includes mammals the type of nucleic acid composing the influenza virus is singular strand RNA the size of the genome of the influenza virus is 13.5 nucleotides or nucleotide base pairs the number of genes found within the genome of the influenza virus is 11 genes within human immunodeficiency virus (HIV) the hosts for the immunodeficiency virus are primates the type of nucleic acid that composes the genome of the human immunodeficiency virus is ssRNA SINGULAR STRAND RNA the size of the genome of the human immunodeficiency virus is 9.7 nucleotides or 9.7 nucleotide base pairs the number of genes within the genome of the human immunodeficiency virus is 9 genes within the herpes simplex virus, type 2 (genital herpes), the host for the herpes simplex virus type 2 genital herpes are humans the nucleic acid composing the genome of the herpes simple virus type 2 genital herpes is dsDNA DOUBLE STRANDED DNA the size of the herpes simple virus type 2 genital herpes genome is 158.4 nucleotides the number of genes within the genome of the herpes simplex virus type 2 genital herpes is 77 genes the size of viral genomes can vary from several thousand to more than a hundred thousand nucleotides the range is several thousand the range of size of viral genomes can vary from SEVERAL THOUSAND NUCLEOTIDES TO A MORE THAN A HUNDRED THOUSAND NUCLEOTIDES the range of size of viral genomes is several thousand nucleotides to more than a hundred thousand nucleotides THE RANGE OF SIZE OF VIRAL GENOMES IS SEVERAL THOUSAND NUCLEOTIDES TO OVER A HUNDRED THOUSAND NUCLEOTIDES the genome of some simple viruses such as the QB virus- this genome of the QB virus, they are only a few thousand nucleotides in length the genome of the QB virus is ONLY A FEW THOUSAND NUCLEOTIDES IN LENGTH AND CONTAIN ONLY A FEW GENES CONTAIN ONLY A FEW GENES the genome in the QB virus is only a few thousand nucleotides in length, and they contain only a few genes there are also other viruses there are these viruses with complex structures, that have many more genes, in comparison to the QB virus that is only a few thousand nucleotides in length the T EVEN PHAGES ARE EXAMPLES MORE COMPLEX VIRUSES WITH MORE NUCLEOTIDES AND THEREFORE LARGER GENOMES

well-studied gene family

A WELL STUDIED GENE FAMILY IS SHOWN BY THE GIVEN FIGURE , OF THE EVOLUTION OF THE GLOBIN GENE FAMILY FOUND IN HUMANS there is a well-documented and well-studied gene family in humans known as the GLOBIN GENE FAMILY the globin gene family is a well-documented and well-studied gene family that is found in humans THE GLOBIN GENES found within this gene family found in humans ENCODE POLYPEPTIDES the globin genes found within this gene family encode polypeptides the polypeptides that these globin genes within this gene family encode ARE POLYPEPTIDES THAT ARE SUBUNITS OF. PROTEINS THAT FUNCTION IN THE BINDING OF OXYGEN the polypeptides coded for by the globin genes within the globin gene family in humans are SUBUNITS OF PROTEINS THAT FUNCTION IN OXYGEN BINDING these coded for polypeptides are subunits of proteins responsible for oxygen binding, the binding of oxygen one protein is HEMOGLOBIN- hemoglobin is a protein coded for by the globin genes, the globin genes code for a polypeptides that function as subunits and compose proteins such as hemoglobin, that are responsible for the binding of oxygen hemoglobin IS A PROTEIN FOUND WITHIN RED BLOOD CELLS hemoglobin is composed of polypeptide subunits that are coded for by globin genes within the globin gene family hemoglobin is a protein that is found within red blood cells THE FUNCTION OF HEMOGLOBIN IS TO CARRY OXYGEN THROUGHOUT THE BODY the function of hemoglobin is to carry OXYGEN THROUGHOUT THE BODY the function of hemoglobin is to carry OXYGEN THROUGHOUT THE BODY THE GLOBIN GENE FAMILY IS COMPOSED OF 14 PARALOGS recall that paralogs are two or more genes that have descended from the same ancestral gene (so they are homologous to one another) that are found within a single species the globin gene family is composed of 14 paralogs THESE 14 PARALOGS WERE ORIGINALLY DERIVED FROM A SINGLE ANCESTRAL GLOBIN GENE these 14 paralogs that compose the globin gene family were originally derived from a SINGLE ANCESTRAL GLOBIN GENE all of the 14 paralogs that compose the globin gene family were originally derived from a SINGLE ANCESTRAL GLOBIN GENE there has been an evolutionary analysis conducted on the globin gene family according to this evolutionary analysis conducted on the globin gene family, THE ANCESTRAL GLOBIN GENE FIRST DUPLICATED ABOUT 500 MILLION YEARS AGO the ANCESTRAL GLOBIN GENE FIRST DUPLICATED ABOUT 500 MILLION YEARS AGO the ancestral globin gene that the 14 paralogs of the globin gene family in humans descended from first duplicated about 500 million years ago, and the ancestral globin gene, when it duplicated about 500 million years ago, BECAME SEPARATE GENES ENCODING MYOGLOBIN AND THE HEMOGLOBIN GROUP OF GENES THE ANCESTRAL GLOBIN GENE FIRST DUPLICATED ABOUT 500 MILLION YEARS AGO, AND THE ANCESTRAL GLOBIN GENE THEN BECAME SEPARATE GENES, the ancestral globin gene duplicated 500 million years ago and became separate genes encoding THE MYOGLOBIN AND THE HEMOGLOBIN GROUP OF GENES the ancestral globin gene that all of the genes of the globin family in humans descended from first duplicated 500 million years ago the ancestral globin gene first duplicated 500 million years ago, and when the ancestral globin gene first duplicated 500 million years ago, it became SEPARATE GENES the ancestral globin gene duplicated and became SEPARATE GENES SEPARATE GENES ENCODING MYOGLOBIN AND THE HEMOGLOBIN GROUP OF GENES the ancestral globin gene duplicated and became separate genes encoding the myoglobin and hemoglobin group of genes THE PRIMORDIAL HEMOGLOBIN GENE DUPLICATE INTO AN ALPHA CHAIN GENE AND A BETA CHAIN GENE the primordial hemoglobin gene that was created out of the duplication of the ancestral globin gene that occurred 500 million years ago and resulted in the formation of genes encoding myoglobin and the hemoglobin group of genes the primordial hemoglobin gene (which was to result in this group of hemoglobin genes descended from the primordial hemoglobin gene and therefore also descended from the ancestral globin gene) DUPLICATED AS WELL the primordial hemoglobin gene that descended from the ancestral globin gene when it duplicated 500 million years ago into genes encoding myoglobin, and genes encoding the group of hemoglobin genes, the primordial hemoglobin gene ALSO DUPLICATED the primordial hemoglobin gene duplicated into the ALPHA CHAIN GENE AND THE BETA CHAIN GENE the primordial hemoglobin gene duplicated into the alpha chain gene and the beta chain gene the alpha chain gene and the beta chain gene were descendants of the primordial hemoglobin gene the alpha chain gene and the beta chain gene that descended from the duplication of the primordial hemoglobin gene that descended from the duplication of the ancestral globin gene ALSO DUPLICATED IN ORDER TO PRODUCE SEVERAL GENES the ALPHA CHAIN GENE that descended from the primordial hemoglobin gene subsequently duplicated in order to produce several descendants, several genes found on CHROMOSOME 16 the BETA CHAIN GENE that also descended from the primordial hemoglobin gene also duplicated subsequently in order to produce several descendants as well, several genes found on CHROMOSOME 11 CURRENTLY THERE ARE 14 GLOBIN GENES 14 PARALOGS WITHIN THE GLOBIN GENE FAMILY recall that paralogs: when there are two genes that descended from an ancestral gene, they are considered homologous to one another, when these two genes are found within the same species, they are considered paralogs THERE ARE 14 GLOBIN GENES CURRENTLY WITHIN THE GLOBIN GENE FAMILY THERE ARE 14 GLOBIN GENES WITHIN THE HUMAN GENES these 14 globin genes are found on 3 DIFFERENT CHROMOSOMES these 14 globin genes of the globin gene family are found on 3 different chromosomes why is it ADVANTAGEOUS TO HAVE A FAMILY OF GLOBIN GENES? why is it advantageous to have a gene family, specifically a gene family of globin genes, consisting of 14 paralogs that all descended from a common ancestral gene and are found within one specific species, humans? ALTHOUGH ALL GLOBIN POLYPEPTIDES all globin polypeptides, all of the polypeptides that compose the globin proteins, all of these polypeptides are considered SUBUNITS OF PROTEINS that are responsible for/play a role in oxygen binding, in the binding of oxygen all globin polypeptides are generally considered subunits of proteins that are responsible for the binding of oxygen HOWEVER DUE TO THE ACCUMULATION OF DIFFERENT MUTATION in THE VARIOUS 14 MEMBERS OF THE GLOBIN GENE FAMILY< mutations that have accumulated due to the evolution, the descent from the ancestral gene to the primordial hemoglobin gene and the myoglobin gene, to the alpha chain gene, the beta chain gene, and subsequent duplications of those in order to end up with several genes on chromosome 16 and chromosome 11 respectively, chromosome 16 for the descendants of the alpha chain gene and chromosome 11 for the descendants of the beta chain gene this accumulation of DIFFERENT MUTATIONS that occurred due to the descent of the 14 paralogs of the globin gene family from the ancestral globin gene result in GLOBINS THAT ARE MORE SPECIALIZED IN REGARDS TO THEIR FUNCTION the accumulation of mutations has resulted in members of the globin gene family that are more particular and specified in their function, more specialized in exactly what they do an example of a globin with a specialized function, more specialized than simply being responsible for binding oxygen MYOGLOBIN IS BETTER AT BINDING AND STORING OXYGEN WITHIN MUSCLE CELLLS myoglobin IS BETTER AT BINDING AND STORING OXYGEN WITHIN MUSCLE CELLS IN PARTICULAR myoglobin is better and binding and storing oxygen in muscle cells in particular, myoglobin, muscles HEMOGLOBINS ARE BETTER AT BINDING AND TRANSPORTING OXYGEN VIA THE RED BLOOD CELLS hemoglobins are better at binding and transporting oxygen via the red blood cells HEMOGLOBINS ARE BETTER AT BINDING AND TRANSPORTING oxygen via the red blood cells hemoglobins are better at binding and transporting oxygen via the red blood cells DIFFERENT GLOBIN GENES ARE EXPRESSED DURING VARIOUS STAGES OF HUMAN DEVELOPMENT DIFFERENT GLOBIN GENES ARE EXPRESSED DURING VARIOUS STAGES OF HUMAN DEVELOPMENT DIFFERENT GLOBIN GENES ARE EXPRESSED AT DIFFERENT STAGES OF HUMAN DEVELOPMENT at varying stages of human development, different globin genes are expressed THE EPSILON AND THE ZETA GLOBIN GENES the EPSILON AND THE ZETA GLOBIN GENES ARE EXPRESSED AT ONE PARTICULAR STAGE OF HUMAN DEVELOPMENT the EPSILON AND THE ZETA GLOBIN GENES ARE EXPRESSED AT ONE PARTICULAR STAGE OF HUMAN DEVELOPMENT, VERY EARLY IN EMBRYONIC LIFE the epsilon and zeta globin genes are expressed very early in embryonic life, during embryonic development, the earliest stages THE ALPHA AND GAMMA GLOBIN GENES ARE EXPRESSED DURING THE SECOND AND THIRD TRIMESTERS OF GESTATION the alpha and gamma globin genes are expressed during the second and third trimesters of gestation the ALPHA and GAMMA GLOBIN GENES ARE EXPRESSED DURING THE SECOND AND THIRD TRIMESTERS OF GESTATION the alpha and the gamma globin genes are expressed during the second and third trimesters of gestation the alpha and the gamma globin genes are expressed during the second and third trimesters of gestation following birth, the ALPHA GLOBIN GENE REMAINS TURNED ON however, following birth, THE GAMMA GLOBIN GENE IS TURNED OFF AND THE BETA GLOBIN GENE IS TURNED ON so recall that during early embryonic development, probably right at the beginning of the first trimester, the epsilon and zeta globin genes are turned on at the beginning of early embryonic development, the epsilon and zeta globin genes are turned on EARLY EMBRYONIC DEVELOPMENT- EPSILON AND ZETA GLOBIN GENES ARE TURNED ON during the second and third trimesters of gestation, the alpha and the gamma globin genes are turned on and expressed DURING THE SECOND AND THIRD TRIMESTERS OF GESTATION, OF FETAL DEVELOPMENT, THE ALPHA AND THE GAMMA GLOBIN GENES ARE TURNED ON AND EXPRESSED THE ALPHA AND GAMMA GLOBIN GENES ARE TURNED ON AND EXPRESSED DURING THE SECOND AND THIRD TRIMESTERS OF GESTATION, DURING THE SECOND AND THIRD TRIMESTERS OF FETAL DEVELOPMENT, THE ALPHA AND GAMMA GLOBIN GENES ARE TURNED ON AND EXPRESSED THE ALPHA AND GAMMA GLOBIN GENES ARE TURNED ON AND EXPRESSED DURING THE SECOND AND THIRD TRIMESTERS OF GESTATION then after birth, after the fetus is fully developed and has been born, THE GAMMA GLOBIN GENE AFTER BIRTH IS TURNED OFF THE GAMMA GLOBIN GENE AFTER BIRTH IS TURNED OFF the gamma globin gene after birth is turned off, THE BETA GLOBIN GENE IS TURNED ON after birth, after full fetal development and the child being born, the gamma globin genes are turned off and no longer expressed (though the gamma globin genes and the alpha globin genes were expressed during the second and third trimesters of gestation) and the BETA GLOBIN GENE IS TURNED ON the alpha globin gene remains turned on after birth this differences in gene expression, the variation in which globin genes of the globin gene family are turned out at particular points of embryonic and fetal development REFLECT THE DIFFERENCES IN THE OXYGEN TRANSPORT NEEDS OF HUMANS the exact for of oxygen transport that humans require changes throughout the embryonic, fetal, and postpartum stages, and different genes of the globin family being turned off and on at these various stages of development reflects that changing requirement various genes of the globin gene family are turned off and on during human development, during embryonic development, fetal development, and postpartum development in order to provide the exact function that the embryo, fetus, or postpartum, born child requires in regards to oxygen transport

ABO blood group alleles

ABO group of antigens, these antigens determine the blood type of an individual, depending upon the antigens that their blood cells have codominance is a another allelic relationship that has to do with the alleles of the ABO blood group in order to understand the concept of codominance and what it has to do with the alleles of the ABO blood group, we need to understand the molecular characteristics of human blood types, the way in which they manifest and are identified the plasma membranes of red blood cells have groups of interconnected sugars (these groups of interconnected sugars are designated as oligosaccharides) that act as surface antigens on these red blood cells oligosaccharides- groups of interconnected sugars on the surface of red blood cells that act as surface antigens what are antigens? they are molecular structures (such as the interconnected sugars oligosaccharides) that are recognized by antibodies of the immune system the antigens of red blood cells are found on their surface there are two different antigen that can be found on the surface of red blood cells: A and B antigens the synthesis of these surface antigens, and the determination of which surface antigens will appear on your red blood cells is dictated by two allies, IA and IB the lowercase i allele is recessive to both the IA and IB alleles a person who is homozygous recessive with the allelic combination ii- O blood type, and does not produce A or B antigens, therefore there are no antigens on the surface of this homozygous recessive individual's red blood cells a person who is homozygous dominant IAIA or heterozygous dominant IAi will be blood type A and have the surface antigen A on their red blood cells a person who is homozygous dominant IBIB or heterozygous dominant IBi will be blood type B and produce surface antigen B, which will be the antigen found on the surface of their red blood cells a person who has the allelic combination of IAIB will have the blood type AB and have the surface antigens A and B on the surfaces of their red blood cells this is an example of codominance- a phenomenon where two alleles coding for two different phenotypic variants of a character are both expressed in a heterozygous individual carrying both of these alleles- one does not win out over the other in regards to genotypic or phenotypic expression the alleles IA and IB are codominant to one another

bacterial chromosomal DNA

BACTERIAL CHROMOSOMAL DNA IS USUALLY A CIRCULAR MOLECULE bacterial chromosomal dna is usually a circular molecule however, some bacteria do indeed have linear chromosomes however recall that bacterial chromosomes tend to be circular in shape, bacteria tend to contain circular chromosomes a typical chromosome within a bacterial cell- A FEW MILLION BASE PAIRS IN LENGTH a typical bacterial chromosome is a few million base pairs in length an example of a bacterial chromosome, the chromosome of a particular strain of Escherichia coli has approximately 4.6 MILLION base pairs the Haemophilus influenza chromosome, the chromosome within the Haemophilus influenza strain of bacteria has roughly 1.8 MILLION BASE PAIRS usually, a bacterial chromosome commonly will contain, consist of A FEW THOUSAND DIFFERENT GENES usually, a bacterial chromosome commonly will consist of a FEW THOUSAND DIFFERENT GENES it will consist of a few thousand different genes a typical bacterial chromosome will consist of a few thousand different genes these few thousand different genes found within a typical bacterial chromosome are typically interspersed and spread throughout the entirety of the chromosome these few thousand different genes found within a typical bacterial chromosome are typically interspersed and spread throughout the entirety of the chromosome STRUCTURAL GENES structural genes are NUCLEOTIDE SEQUENCES THAT ENCODE PROTEINS these structural genes are nucleotide sequences that encode proteins structural genes are nucleotide sequences that encode, code for proteins these structural genes account for the majority of DNA the majority of DNA is composed of structural genes, nucleotide sequences that encode proteins

binary fission

BACTERIAL SPECIES ARE USUALLY UNICELLULAR however, some individual bacteria, that are considered separate, independent, distinct unicellular entities can associate with one another in order to form PAIRS CHAINS OR CLUMPS SOMETIMES A MULTITUDE OF UNICELLULAR ENTITIES CAN ASSOCIATE WITH ONE ANOTHER IN ORDER TO FORM PAIRS CHAINS CLUMPS unicellular entities can associate with one another in order to form pairs, chains, and clumps EUKARYOTES CONTAIN THEIR CHROMOSOMES WITHIN A PARTICULAR ENTITY THE NUCLEUS, separate from the rest of the cell, their genetic material found in the form of chromosomes is contained within this entity at the center of the cell, the nucleus however, within bacteria, their genetic material is found in the form of circular chromosomes, and their genetic material found in the form of circular chromosomes is in direct contact with the cytoplasm within the cell the genetic material found within bacteria, that are found in the form of circular chromosomes, come into direct contact with the cytoplasm found within the prokaryotic cell the capability of bacteria to divide is ASTOUNDING it is v intriguing the way that bacteria divide and then proliferate in order to form cultures and colonies of themselves there are particular species, such as Escherichia coli Escherichia coli is a common bacterium of the intestine Escherichia coli is A COMMON BACTERIUM OF THE INTESTINE, and it has the capability of being able to divide every 20 to 30 minutes Escherichia coli, a common bacterium found within the intestine, has the capability of dividing and thus proliferating every 20 to 30 minutes PRIOR TO BACTERIAL CELL DIVISION, bacteria undergoing cell division in order to form two identical daughter cells each, the original bacterial cells replicate their chromosomal DNA the bacterial cells replicate all of their chromosomal DNA prior to the process of cellular division occurring thus, 2 identical copies of their genetic material are created each bacterial cell, after DNA replication, where their chromosomal DNA is copied/replicated, now have 2 copies of their entire genome within them, 2 copies of all of their chromosomal DNA within them, that they will be able to distribute to their daughter cells one DNA replication occurs, and the bacterial cells contain 2 copies of their DNA, 2 copies of all of their chromosomal DNA, they are ready to undergo the process of binary fission the bacterial cell divides and proliferates into two daughter bacterial cells through the implementation of the process of binary fission during the event of binary fission, the original bacterial cell is able to separate into two identical daughter cells after DNA replication in the original bacterial cell has occurred the two daughter cells separate from one another (forming from the original bacterial cell) by the formation of a septum each identical daughter cell proliferating from the original bacterial cell receives 1 copy of the original cell's genetic material (There were 2 copies of the original cell's genetic material after the process of replication occurred within the cell, and therefore, 1 copy each was able to be distributed evenly to each daughter cell, of which there are 2, 2 daughter cell proliferating from the original bacterial cell) each cell receives 1 copy of the chromosomal genetic material found in the original bacterial cell rare mutations can sometimes occur during the process of binary fission, it is possible that rare mutations come about, that can make the daughter cells not genetically identical despite proliferating from the same original bacterial cell however the daughter cells that proliferate from the original bacterial cell are usually identical to one another

epistasis

Bateson and Punnett discovered an unexpected gene interaction when they were implementing and studying cross involving the sweet pea, Lathyrus odoratus the wild sweet pea (presumably homozygous dominant or heterozygous dominant allelic combination) has purple flowers- so purple is the dominant trait Bateson and Punnett managed to created several true-breeding mutant sweet pea plants with white flowers they decided to implement a cross bw a true breeding (presumably homozygous dominant) purple flower sweet pea plant and a true breeding (presumably homozygous recessive) white flower sweet pea plant the first filial generation of sweet pea plants contained all purple flower sweet pea plants the first filial generation of sweet pea plants self-fertilized themselves, and purple and white flowered sweet pea plants were found in a purple : white 3:1 ratio Bateson and Punnett conducted another cross with surprising results they crossed two different varieties of white-flowered sweet pea plants (so they both had white flowers, but were perhaps different in regards to other phenotypic expressions and therefore genotype) the offspring of this cross was all purple flowers, which followed a markedly non-Mendelian pattern of inheritance the first filial generation with purple flowers was allowed to self fertilize the second filial generation resulting from the self-fertilization of the purple flowered sweet pea plants of the first consisted of purple and white flowers the ratio of purple to white was 9:7 from the above experiment, Bateson and Punnett determined that two different genes both influence the color of the flowers of sweet pea plants C (one purple-color producing allele) is dominant to c (a recessive allele coding for white flowers) P (another purple-color producing allele) is dominant to p (another recessive allele coding for white flowers) the allelic combination cc or pp masks the P or C alleles, and codes for white color, the pea plant with an allelic combination containing cc or pp will present with white flowers

bateson and punnett

Bateson and punnet discovered two traits that did not assort independently Bateson and punnet discovered two traits that did not assort independently Bateson and punnet discovered two traits that did not assort independently Bateson and punnet discovered two traits that did not assort independently there was an early study indicating that some traits may not assort independently from one another this early study indicating that some traits may not independently assort from one another was carried out by William Bateson and Reginald Punnet in 1905, an early study indicating that some traits may not assort independently from one another according to Mendel's law of independent assortment, a dihybrid cross bw two individuals, heterozygous for two genes, should result in a 9:3:3:1 phenotypic ration amongst the offspring according to Mendel's law of independent assortment, a dihybrid cross bw two individuals that are both heterozygous for two genes should yield a 9331 phenotypic ratio amongst the offspring created from this cross bw two individuals that are both heterozygous for two genes the above result is conditional on the law of independent assortment always being implemented however there was a surprising result that occurred when Bateson and Punnett conducted a cross in the sweet pea that involved two different traits, flower color and pollen shape there was a surprising result that occurred when these two individuals crossed sweat peas that involved two different traits flower color and pollen shape there is a figure that showcases this experiment the two individuals, William Bateson and Reginald Punnet began by tossing a true breeding strain (homozygous, being able to produce the same result over and over throughout generations of self fertilization, no deviation) with purple flowers (therefore having the allelic combination PP, the homozygous dominant allelic combination coding for the dominant trait of purple flowers) and long pollen (having the allelic combination LL, the homozygous dominant allelic combination coding for the dominant variant of long pollen within the pollen length trait) they crossed this true breeding sweet pea with purple flowers PP and long pollen LL to another true breeding sweet pea this other true breeding sweat pea was a sweet pea with red flowers (having the homozygous recessive allelic combination pp, coding for the recessive variant of red flowers for the trait flower color) and short pollen (coded for by the homozygous recessive allelic combination ll, coding for the recessive variant short pollen within the category of the character of pollen length) when the F1 generation was created due to the cross bw these two true breeding individuals, these two true breeding sweet pea plants, one having the dominant traits of purple flowers and long pollen (and having homozygous dominant allelic combinations resulting in the aforementioned dominant traits of purple flowers and long pollen), and the other having the recessive traits of red flowers and red pollen (coded for by the homozygous recessive allelic combinations that coded for the recessive traits of red flowers and short pollen) when the f1 generation was created due to the cross bw these two true breeding sweet pea plants, all of the plants within the f1 generation had purple flowers and long pollen, all having the heterozygous allelic combinations and allelic pairing of PpLl all of these plants, as expected within the f1 generation maintained the dominant traits of purple flowers and long pollen, a parental offspring that mimicked the pairing of traits found in one of the parents, the homozygous dominant parent with purple flowers and long pollen when the f1 generation self fertilized, there were surprising results found within the f2 generaiton when the f1 generation self fertilized there were surprising results found within the f2 generation even hough the F2 generation had four different phenotypic categories, which was expected, the observed numbers of offspring did not conform to a 9331 ration as was expected Bateson and Punnett found that the F2 generation ha a much greater proportion of the two phenotypes found in the parental generation the f2 generation had a much greater proportion of the two phenotypes the phenotypic combinations found within the parental generation what were the phenotypic combinations found within the parental generation the f2 generation had a much greater proportion of the two phenotypes, the two phenotypic combinations found within the parental generation the phenotypic combination of purple flowers and long pollen and the phenotypic combination of red flowers and short pollen that were phenotypic combinations present in the parental generation that produced the f1 generation that self fertilized in order to produce the f2 generation there were higher proportions within the f2 generation of the phenotypic combinations that were found in the parental generation, the two phenotypic combinations and pairing being purple flowers and long pollen and red flowers and short pollen therefore they suggested that the transmission of these two traits from the parental generation to the f2 generation was somehow coupled and not easily independently assorted, which is why the expected phenotypic ratio was not found in the f2 generation however, Bateson and punnet did not realize that this coupling was due to the linkage of the flower color gene and the pollen shape gene on the same chromosome

Bridges gene modifier effect discovery

Bridges in his experiments with Drosophila melanogaster observed an 8:4:3:1 ratio this ratio was observed bc the cream-eye gene can modify the x-linked eosin allele, but cannot modify the red or white alleles epistasis definition reminder: the alleles of a given gene (the allelic combination of a given gene) masks the phenotypic effects of another gene (and its allelic combination) there are cases (gene modifier cases) where two genes undergo an interaction that influences the expression of the same phenotypic trait, but the interaction bw the two genes and their two allelic combinations results in the phenotype being modified, not one of them being masked Calvin Bridges looked at how one gene modifies the phenotypic effect (the phenotypic expression that another gene codes for) of an X-linked eye color gene w+- this x-linked allele is dominant, and codes for red eyes w- this x-linked allele is recessive, and codes for white eyes Thomas Hunt Morgan and Calvin Bridges found another allele of this gene: w-e- this is the eosin allele that goes for pale orange eyes the red w+ allele is dominant to the w-e allele the expression of the w-e eosin allele depends upon the number of copies of this allele if females have two copies of this allele, then they will have eosin pale orange eyes (they have two alleles coding for an eosin eye color, one on each X-chromosome) if females are heterozygous for the eosin allele and white allele, they will have light-eosin eyes (recall that the allele coding for white eyes, w is not dominant to the allele coding for pale orange eyes, w-e) when these two alleles are in a heterozygous allelic combination (one X chromosome having the allele w and the other X chromosome having the allele w-e, the organism will present with light eosin eyes) when looking at true breeding cultures of eosin-eyed flies, sometimes Bridges found a fly with a noticeably different eye color (Within a true breeding scenario that should have resulted in the consistent propagation of the same trait generation after generation) this new eye color was cream color two different explanations for this cream colored phenotype 1) there could be a mutation that changed the eosin allele coding for pale orange eosin eye color to an allele coding for cream eye color 2) there could be a different gene that gain a mutation, and this mutation resulted in the modification of the phenotypic expression of the eosin pale orange eye allele (genetic modifier) the second explanation is describing a gene interaction he carried out crosses in order to understand which explanations fit the crosses he c married out were males with cream colored yes to wild type females with red eyes the first filial generation of flies mated with one another (this first filial generation consisted of organisms with red eyes) in the second filial generation, al of the F2 females had red eyes the options for male offspring in the F2 generation were red, eosin/pale orange or cream eyes the hypothesis of this experiment is that the cream colored eyes that some fruit flies have are due to the effect of an allele that is in the same gene/allelic combination as the eosin allele, or it is due to a second gene that is able to modify the phenotypic expression of the eosin allele the presence of the allelic combination caca can modify the phenotype coded for by the Xw-e allele the presence of this allelic combination caca cannot modify the phenotype coded for by the Xw+e

unbalanced translocation

CARRIERS OF A RECIPROCAL TRANSLOCATION ARE AT RISK OF HAVING OFFSPRING WITH AN UNBALANCED TRANSLOCATION carriers of a reciprocal translocation are at risk of having offspring with an unbalanced translocation in an unbalanced translocation, there is an alteration to the total amount of genetic material in an unbalanced translocation, significant portions of genetic material are duplicated and/or deleted in an unbalanced translocation, significant portions of genetic material are duplicated and/or deleted UNBALANCED TRANSLOCATIONS are generally associated with phenotypic abnormalities in the individual with unbalanced translocations, where there is a significant amount of genetic material that is duplicated or deleted, or it can even result in lethality, where the offspring, the individual with unbalanced translocations may not live due to the significant duplication or deletion of genetic material HOW DOES A PERSON WITH A BALANCED TRANSLOCATION where the total amount of genetic material is not impacted, how does this individual with a balanced translocation produce gametes and offspring with an unbalanced translocation? how in the world does this happen there is an example found in the inherited human syndrome- familial Down syndrome provides an example of how an individual with a balanced translocation can produce an offspring with an unbalanced translocation how can an individual with a balanced translocation and no alteration to the total amount of its genetic material produce an offspring with an unbalanced translocation, an alteration to its total amount of genetic material, and possible phenotypic consequences or lethality a person with a normal phenotype may have one copy of chromosome 14, one copy of chromosome 21, and one copy of a chromosome that is a fusion/a combination of chromosome 14 and 21 the individual has a normal phenotype bc the total amount of genetic material is present, there is the presence of chromosome 14, chromosome 21, and a fusion/combination of chromosome 14 and 21, which results in a total and unaltered amount of genetic material, no alteration to the total amount of genetic material, but merely a rearrangement in genetic material in regards to the fusion of chromosome 14 and chromosome 21 in addition to the individual chromosome 14 and 21 there is the exception of the short arms of these chromosomes that were lost and degraded due to the fusion of chromosome 14 and 21 into a hybrid combination chromosome, so technically the individual does not have all of the genetic material, but rather has all of the vital genetic material as the p arms of chromosome 14 and 21 do not contain vital genetic material, therefore the fact that due to the combination and fusion of chromosome 14 and chromosome 21, the p arms of those chromosomes were lost, there is no substantial genetic and therefore no substantial phenotypic consequence bc the genes contained within the p arms of these chromosomes are not vital during meiosis these three types of chromosomes replicate and segregate from one another during meiosis, chromosome 14, chromosome 21, and the chromosome 14/21 hybrid separate from one another HOWEVER bc the three chromosomes cannot separate evenly, due to the uneven number of chromosomes, there are 6 POSSIBLE TYPES OF GAMETES THAT MAY BE PRODUCED due to the fact that these 3 chromosomes cannot segregate properly due to their uneven number during meiosis, there are 6 possible gametes that can be produced due to the unusual paths of segregation that these chromosomes, chromosomes 14, 21, and the chromosome 14/21 fusion can take ONE GAMETE IS NORMAL another gamete is a BALANCED CARRIER OF A TRANSLOCATED CHROMOSOME, a fusion of the two chromosomes, chromosome 14 and 21, but contained a balanced amount of genetic material despite the translocation, so this gamete is relatively normal however, the 4 other possible gametes that can be produced by an individual with chromosome 14, chromosome 21, and the chromosome combination of chromosome 14 and chromosome 21 are UNBALANCED either containing too much or too little genetic material from chromosome 14 or 21 these other 4 possible gametes either contain too much or too little genetic material from chromosome 14 or 21 one gamete contains excess chromosome 21 genetic material, there is a genetic imbalance where there is some of chromosome 14, but not all of it that is required, and there is too much of chromosome 21 there is another possible gamete, where only chromosome 14 is present in the gamete, and chromosome 21 is completely absent, so there is an enormous lack of genetic material, as any offspring formed from this gamete will have only 1 chromosome 21, rather than the two that it requires there is a third possible gamete out of the four with huge genetic imbalances, where the gamete only has chromosome 21 and no chromosome 14, there is a substantial and impactful lack of genetic material in regards to chromosome 14 missing from the gamete, any offspring formed from this gamete with a normal gamete, will be missing one of its chromosome 14's the fourth possible gamete in the gametes that will have huge imbalances of genetic material, either large duplications or deletions, is where there is an excess amount of chromosome 14, and a deficient amount of chromosome 21, resulting in a zygote (when this abnormal gamete is combined with a normal gamete) that has excess chromosome 14 genetic material and a severe deficiency of chromosome 21, and therefore a severe deficiency of chromosome 21 genetic material these past 3 aforementioned gametes containing enormous and substantial duplications or deletions of genetic material result in nonviable zygotes, when these abnormal gametes with substantial duplications and/or deletions combine with a normal gamete, they will result in zygotes with extremely unbalanced amounts of chromosome 14 and chromosome 21 genetic material, substantial duplications and/or duplications, and that will be lethal, and the zygote will not develop into a fetus the gamete resulting from an individual with chromosome 14, chromosome 21, and the fusion chromosome 14 and 21, where there is an excess of chromosome 21 and a deficiency of chromosome 14, will not result in lethality when this abnormal gamete with unbalanced amounts of genetic material in regards to chromosome 14 and chromosome 21 is combined with a normal gamete with normal amounts of genetic material particularly in regards to chromosome 14 and chromosome 21, a zygote will develop into a fetus and be born as a baby presenting with familial Down syndrome, but the genetic imbalance in this individual will simply cause phenotypic consequences, not lethality the unbalanced gametes may be inviable, or they could combine with a normal gamete the three offspring on the right formed from chromosomes with particular substantial duplications and/or deletions of the genetic material contained within chromosome 14 and 21 are not viable and will not survive however, there is the unbalanced gamete that carries excess genetic material contained within chromosome 21, and has a slight deficiency in regards to the genetic material contained within chromosome 14, and a zygote formed from the union bw this abnormal genetically imbalanced gamete and a normal genetically balanced gamete will have familial Down syndrome (the gamete contributing to this kind of viable yet phenotypically affected and impacted zygote is a game with one copy of chromosome 21 and then a fused chromosome containing chromosome 14 and chromosome 21, the q arms of both these chromosomes) potentially this may be a viable zygote due to the fact that simply the p arms of two chromosomes are missing, which do not contain genetically vital material, and then phenotypic consequences arise bc an entire chromosome 14 is missing, which is a significant deficiency in regards to genetic material this offspring with familial Down syndrome has three copies of the genes that are found on the long q arm of chromosome 21 the offspring with familial Down syndrome has 3 copies of the genes that are found on the long q arm of chromosome 21, and this contributes to the phenotypic consequence of familial down syndrome there is an individual shown in the figure who has CHARACTERISTICS SIMILAR TO THOSE OF AN INDIVIDUAL WHO HAS THE MORE PREVALENT FORM OF Down syndrome, the more prevalent form of Down syndrome that results from 3 copies of chromosome 21, rather than simply three copies of the q arm of chromosome 21, and 1 missing copy of the p arm of chromosome 21

variation in chromosome number

CHROMOSME STUCTRURE chromosome structure can be altered in a variety of ways chromosome structure, the structure of chromosomes can be altered in a variety of ways chromosome structure the structure of chromosomes can be altered in a variety of ways THE TOTAL NUMBER OF CHROMOSOMES CAN ALSO VARY this is a different genre of chromosomal aberration, the first we talked about was mutations within the chromosomes themselves such as duplications, deletions, translocations, robertsonian translocations, reciprocal translocations, unbalanced translocations, etc, chromosomal aberrations that affect chromosome structure now we will talk about chromosomal aberrations that affect chromosome number, perhaps the specific number of a particular type of chromosome, the number of copies of a particular chromosome within an organism's genome, or the total number of sets of chromosomes within an organism's genome VARIATIONS IN CHROMOSOME NUMBER CAN BE CATEGORIZED IN TWO WAYS there can be variation in the total number of sets of chromosomes there can also be variation within the number of particular chromosomes within a set, the copies of a particular chromosome within a set within an individual's genome

variation in chromosome structure

CHROMOSOMES FOUND WITHIN THE NUCLEI OF EUKARYOTIC CELLS CONTAIN LONG AND LINEAR DNA MOLECULES chromosomes that are found within the nuclei of eukaryotic cells constitute and contain long and linear dna molecules chromosomes found within the nuclei of eukaryotic cells contain long and linear DNA molecules these long and linear DNA molecules that compose the chromosomes we find within the nuclei of eukaryotic cells CARRY HUNDREDS OR EVEN THOUSANDS OF GENES so within the nuclei of eukaryotic cells, we find chromosomes, each individual chromosome is composed of a v long and linear DNA molecule, that carries hundreds or thousands of genes this long and linear DNA molecule that constitutes an individual chromosome encodes hundreds or even thousands of genes in the following section, we are going to explore how this chromosomal structure, consisting of a long and linear DNA molecule that encodes hundreds or even thousands of genes can be altered and changed SEGMENTS OF A CHROMOSOME CAN BE LOST DUPLICATED OR REARRANGED IN A NEW WAY segments of a chromosome can be: -LOST/DELETED -DUPLICATED/REPLICATED -REARRANGED IN A NEW WAY/INVERTED we are also going to examine the cellular mechanisms, the cellular entities involved in these alterations of chromosomes structure, where portions of these chromosomes can be lost/deleted, duplicated/replicated, or rearranged in a new way there are also unusual events that can occur during meiosis these unusual events that can occur during meiosis may affect how altered chromosomes are transmitted from parents to offspring unusual events that can occur during the gametogenesis process of meiosis may affect HOW ALTERED CHROMOSOMES ARE TRANSMITTED FROM PARENTS TO THEIR OFFSPRING the events of mitosis can impact the methods by which altered chromosomes are transmitted from parents to offspring we are also going to investigate examples where chromosomal alterations, changes in the structure of chromosomes or the total number of chromosomes found in the somatic cells of a eukaryotic organism affect an organism's phenotype the way an organism presents in regards to its morphological, physiological, and behavioral characteristics in order for researchers to appreciate and understand variation and changes within chromosomal structure, the researchers need to have a reference point for the structure of normal chromosomes in order to appreciate, identify, and acknowledge when there is variation in chromosomal structure, researchers need to have an established reference point for the structure of normal chromosomes, so they can properly and confidently identify any deviations from this established and known structure what do the normal chromosomes of a species look like? how do we establish this reference point for the structure of normal chromosomes? we establish this reference point for the structure of normal chromosomes in the following way: a cytogeneticist, a cytogeneticist is an individual who studies chromosomes microscopically this individual, a cytogeneticist who studies chromosomes microscopically, utilizes a microscope in order to study the structure and number of chromosomes found within a eukaryotic organism's somatic cells this cytogeneticist will examine chromosomes from several members of a given species the CYTOGENETICIST WILL EXAMINE CHROMOSOMES FROM SEVERAL MEMBERS OF A GIVEN SPECIES the cytogeneticist will examine chromosomes from several members of a given species, will examine the cells of several members of a given species, and analyze the chromosomes within these cells in the majority of cases, TWO PHENOTYPICALLY NORMAL INDIVIDUALS OF THE SAME SPECIES, when examined by a cytogeneticist, will be found to have the same number and types of chromosomes when individuals of the same species are examined, when the genotypes and the chromosomes of these two individuals belong to the same species are examined (their genetic material, their chromosomes will be examined by a cytogeneticist, who will analyze and create a karyotype, a full and complete complement of the chromosomes found within the nuclei of their cells, organized according to size, and paired according to level of homology), within the cells of these two individuals belonging to the same species, within the nuclei of these cells, they will be found to have the same number and types of chromosomes, because they belong to the same species and are both phenotypically normal (meaning that their genotype will be reflective of a normal, healthy organism of that species, without any chromosomal mutations in structure or number, therefore giving a cytogeneticist a reference point for a normal complement of chromosomes for an individual of a species to possess) in order to determine the chromosomal composition of a species, THE CHROMOSOMES FOUND WITHIN ACTIVELY DIVIDING CELLS ARE EXAMINED MICROSCOPICALLY the chromosomes within actively dividing cells, chromosomes within cells that are going through the cell cycle and undergoing mitosis and cytokinesis are examined in order to determine the chromosomal complement of a species these chromosomes within the nuclei of actively dividing cells are analyzed through the utilization of a microscope we can look at micrographs of chromosomes we are looking at the micrographs of chromosomes of 3 species: a human a fruit fly a corn plant looking at the micrographs of these 3 types of organisms, we can see the following a human organism, a eukaryotic organism, a human has 46 chromosomes, composed of 23 pairs chromosomes, 2 to a pair making for a chromosome complement composed of 46 chromosomes a fruit fly has 8 chromosomes total, 4 pairs of chromosomes, 2 to a pair, making for a chromosome complement of 8 chromosomes total corn has 20 chromosomes total, 10 pairs of chromosomes, 2 chromosomes to a pair, making for a corn chromosome complement of 20 chromosomes total except for the sex chromosomes, which differ bw males and females, the sex chromosomes combination, presentation differs amongst the sexes of the same species that is where you will find chromosomal difference besides the sex chromosomes that determine the sex of an organism, the majority of the members of the same species HAVE V SIMILAR CHROMOSOMES the majority of the members of the same species have v similar chromosomes (the only place they usually differ is in regards to sex chromosomes, as these are the chromosomes that are guaranteed to differ as one moves a genetic analysis from one individual of a species to another, and the sex of individuals obviously differs amongst individuals of a species) an example showcasing this similarity amongst individuals of the same species in regards to their autosomes, the OVERWHELMING MAJORITY OF HUMANS have 46 chromosomes contained within their somatic cells the majority of humans have 46 chromosomes contained within their somatic cells by comparison, the chromosomal compositions and complements of species that are differently related, will be definitively and markedly different from one another an example of this difference is that when we are looking at humans and fruit flies, and the chromosomal complements of the individuals in these two v distantly related species, we will find that in the somatic cells of humans, there are 46 chromosomes that is the norm for humans, while in fruit flies, the norm is 8 chromosomes within each of a fruit fly's somatic cell

changes in chromosome structure

CHROMOSOMES TYPICALLY COME IN A VARIETY OF SHAPES AND SIZES chromosomes naturally vary in regards to their shapes and sizes HOW CAN THE STRUCTURES OF NORMAL CHROMOSOMES BE MODIFIED? in what ways can the structures of normal chromosomes be modified? in what ways can the structures of normal chromosomes be altered or modified the structures of normal chromosomes can be changed and modified in a number of ways IN SOME CASES THE TOAL AMOUNT OF GENETIC MATERIAL WITHIN A SINGLE INDIVIDUAL CHROMOSOME CAN BE DRAMATICALLY AND SUBSTANTIALLY ALTERED in some cases, the total amount of genetic material within a single individual chromosome CAN BE DRAMATICALLY AND SUBSTANTIALLY ALTERED, in some cases the total amount of genetic material within a single individual chromosome can be dramatically and substantially altered, can be increased or decreased significantly and substantially, significantly THE GENETIC MATERIAL IN ONE OR MORE CHROMOSOMES MAY BE REARRANGED AS WELL the genetic material in one or more chromosomes can be rearranged which will showcase change in the chromosomal structure, but not necessarily impact the total amount of genetic material within the nucleus containing these chromosomes the total amount of genetic material may not be affected despite the alteration of chromosomes, the rearrangement of genetic material genetic mutations are CATEGORIZED AS DELETIONS DUPLICATIONS INVERSIONS TRANSLOCATIONS deletions and duplications- these are mutations that CAUSE CHANGES IN THE TOTAL AMOUNT OF GENETIC MATERIAL FOUND WITHIN A SINGLE CHROMOSOME deletions and duplications are mutations that cause changes in the total amount of genetic material found within a single chromosome deletions and duplications are mutations that cause changes within the total amount of genetic material found within chromosomes, the total amount of genetic material found within chromosomes is altered we are looking at a figure where chromosomes are labeled according to their normal and established, verifiable gene banding patterns DELETION- when a deletion occurs, a segment of the chromosomal material is missing when a deletion occurs, a segment of a chromosome is missing the AFFECTED CHROMOSOME that has experienced deletion is DEFICIENT IN A SIGNIFICANT AMOUNT OF GENETIC MATERIAL the affect chromosome that has experienced deletion is deficient in a significant amount of geneticmaterila the affected chromosome that has experienced deletion is deficient in a significant and substantial, noticeable amount of genetic material in a deletion, a notable amount of genetic material is missing from a chromosome, the affect chromosome is deficient in a particular amount of genetic material that has been deleted DEFICIENCY IS ANOTHER TERM UTILIZED in order to describe a deletion in a chromosome deficiency is another term used to designate A MISSING REGION OF A CHROMOSOME DUPLICATION- a duplication occurs when a section of a chromosome is REPEATED compared with the normal chromosome a chromosomal duplication is where a segment of a chromosome is duplicated, replicated, repeated, in comparison to the normal structure of the chromosome, where there would be only one copy of that segment INVERSIONS AND TRANSLOCATIONS ARE CHROMOSOMAL REARRANGMENTS inversions and translocations are chromosomal rearrangements that do not affect the overall amount of genetic material found within a chromosome the chromosomal genetic material is rearranged, but the totality of genetic material does not change AN INVERSION- this involves a change in the direction of the genetic material along a single chromosome if there is an inversion in a chromosome, this term designates an alteration in the directionality of genetic material on single chromosome, a change in the directionality of a genetic sequence on a chromosome, on a single chromosome what is an example of an inversion if you look at the given figure, on one chromosome, there is a segment that has undergone inversion, that has been inverted, so the directionality of this chromosomal segment has been changed due to the directionality of this chromosomal segment being changed due to an inversion, the order of the 4 G bands found within this chromosomal segment has been flipped around, the opposite of the order that the G bands are found in when this chromosomal segment is not inverted and is in its normal conformation TRANSLOCATION- a translocation is a mutation that also does not affect the totality of genetic material A TRANSLOCATION OCCURS WHEN ONE SEGMENT OF A CHROMOSOME BECOMES ATTACHED TO A DIFFERENT CHROMOSOME OR THIS SEGMENT OF A CHROMOSOME BECOMES ATTACHED TO A DIFFERENT PORTION OF THE SAME CHROMOSOME THAT IT WAS CUT FROM a translocation occurs when one segment of a chromosomes becomes attached to a different chromosome or becomes attached to another part of the chromosome it came from A SIMPLE TRANSLOCATION- this is a translocation where a single piece of a chromosome is attached to another chromosome, or attached to another part of the same chromosome that the chromosomal segment comes from, it is a simple relocation, translocation of genetic material to another chromosome, or another part of the chromosome that the chromosomal segment comes from A RECIPROCAL TRANSLOCATION- this is a different type of translocation, this is where TWO NON HOMOLOGOUS DIFFERENT TYPES OF CHROMOSOMES EXCHANGE PIECES two non homologous, different and distinguished chromosomes exchange chromosomal segments, two NON HOMOLOGOUS CHROMOSOMES BELONG TO DIFFERENT PAIRS EXCHANGE CHROMOSOMAL SEGMNET this produces TWO ABNORMAL CHROMOSOMES, each abnormal chromosome carrying translocations in reciprocal translocation, two non homologous chromosomes exchange chromosomal segments, and therefore each chromosome participating in the reciprocal translocation now carries translocations due to a reciprocal translocation occurring there are now two abnormal chromosomes that carry translocations, rather than the one that would result from a simple translocation recall that a simple translocation is where a chromosomal segment is attached to a different chromosome or a different part of the chromosome that this chromosomal segment comes from, resulting in one abnormal chromosome carrying a translocation

chromosomal identification

CYTOGENETICS have a multitude of methods that they utilize in order to classify and identify chromosomes cytogeneticists have a multitude of methods that they utilize in order to classify, identify, and designate chromosomes what are the three most commonly used features that cytogeneticists utilize in order to identify and designate chromosomes? what are the three most commonly used features that cytogeneticists utilize in order to identify, classify, and designate chromosomes? the three MOST COMMONLY USED FEATURES THAT CYTOGENETICISTS UTILIZE IN ORDER TO CLASSIFY AND IDENTIFY CHROMOSOMES ARE THE FOLLOWING: -LOCATION OF THE CENTROMERE -SIZE -BANDING PATTERNS OF THE CHROMOSOMES THAT ARE REVEALED WHEN THE CHROMOSOMES ARE STAINED, WHEN THEY ARE TREATED WITH GIEMSA WHICH STAINS THEM AND SHOWCASES THESE BANDING PATTERNS that assist cytogeneticists in being able to distinguish, classify, and designate chromosomes CHROMOSOMES CAN BE CLASSIFIED AS: -metacentric -submetacentric -acrocentric -telocentric chromosomes can be classified as METACENTRIC- metacentric delineates the fact that the CENTROMERE OF THIS CHROMOSOME IS LOCATED NEAR THE MIDDLE OF THE CHROMOSOME metacentric designates the fact that the centromere of the metacentric chromosome is located near the middle of the chromosome chromosomes can be classified as SUBMETACENTRIC- submetacentric delineates that fact that THE CENTROMERE IS SLIGHTLY OFF CENTER the term submetacentric used to delineate and designate a chromosomes designates the fact that the centromere of this submetacentric chromosome is slightly off center chromosomes can also be classified as ACROCENTRIC the term acrocentric for acrocentric chromosomes is utilized to designate the fact that the CENTROMERE IS SIGNIFICANTLY OFF CENTER BUT NOT AT THE END the centromere is significantly off center but not at the end of the chromosome in the designation of acrocentric chromosomes, the term acrocentric designates the the centromere of this acrocentric chromosome is significantly off center but not at the end of the chromosome the centromere of the acrocentric chromosome is significantly off center but not at the end of the acrocentric chromosome chromosomes can also be classified as TELOCENTRIC- this designation of telocentric means that the CENTROMERE IS LOCATED AT ONE END OF THE CHROMOSOME the designation of telocentric means that within a telocentric chromosome, the centromere is located at the very end of this chromosome THE CENTROMERE IS NEVER EXACTLY IN THE CENTER OF A CHROMOSOME the CENTROMERE IS NEVER EXACTLY IN THE CENTER OF A CHROMOSOME it is never located at the exact center of the chromosome therefore, due to the centromere never being located at the exact center of the chromosome, each chromosome has two designated and stint arms each chromosome, due to the centromere never being located in the exact center of the chromosome, each chromosome has a short arm and a long arm each chromosome has a short arm and a long arm the short arm is designated as the P ARM the petit, the short arm, the p stands for petit, the p arm of the chromosome is the short arm the long arm is designated as the q arm, the longer arm (bc q comes after the letter p in the alphabet) IN THE CASE OF TELOCENTRIC CHROMOSOMES, where the centromere is located at the v end of the chromosome, the p arm will be extremely short, or it will be nonexistent

Chargaff experimentation

Chargaff Chargaff found that dna has a biochemical composition in which the amount of A equals T and the amount of G equals C Chargaff found that dna has a biochemical composition a specific biochemical composition in which the amount of the nitrogenous base A equals the amount of the nitrogenous base T and the amount of the nitrogenous base G equals the amount of the nitrogenous base C There was another piece of information that led to the discovery of the double helix structure There was another piece of information that led to the discovery of the double helix structure This additional piece of information that led to the discovery of the double helix structure came from studies conducted and implemented by Erwin Chargaff In the 1940s and 1950s Erwin Chargaff pioneered many of the biochemical techniques for: Isolation Purification Measurement of nucleic acids from living cells In the 1940s and 1950s Erwin chargaff pioneered many of the biochemical techniques for Isolation, purification, and measurement of nucleic acids of living cells This was not a trivial undertaking at all, because the biochemical composition of living cells is extraordinarily complex, and therefore his development and pioneering of biochemical tehcniques utilized to isolate purify and measure nucleic acids within living cells was quite impressive At the time of chargaff's work and implemented experiments, scientists already recognized and understood that the building blocks of DNA are nucleotides that contain the bases adenine, thymine, guanine or cytosine Chargaff then analyzed the basic composition of DNA He analyzed the composition of dna by isolating dna from a multitude of species He expected that the results of his analysis of the composition of dna from a multitude of species may provide clues concerning the ultimate and potentially verifiable structure of dna The experimental protocol of chargaff is described He began with various types of cells a multitude a variety of different types of cells His began his implemented experiments with a variety of types of cells He began his implemented experiments with a multitude of a variety of cells The chromosomes were extracted from these cells, from these variegated cells and then these chromosomes extracted from this variety of cells were treated with protease The chromosomes that he extracted from the variety of cells he implemented his experiments on, the chromosomes that he extracted from this multitude of cells were treated with protease These chromosomes were treated with protease in order to separate the dna in particular from chromosomal proteins These chromosomes were treated with protease in order to separate the dna in particular from chromosomal proteins The dna that came about due to the treatment of the extracted chromosomes with protease, that separated the dna from the chromosomal proteins, the dna that came about due to chromosome extraction and protease treatment was then subjected to a strong acid treatment The strong acid treatment that the dna was subjected to cleaved the bonds bw sugars and bases The strong acid treatment that the dna was subjected to cleaved the bonds bw sugars and bases The strong acid treatment that the dna was subjected to cleaved the bonds bw sugars and nitrogenous bases within the dna, cleaved the bonds bw the sugars and nitrogenous bases that composed the dna Therefore the strong acid treatment released the individual bases from the dna strands Therefore the strong acid treatment released the individual bases from the dna strands, as the strong acid treatment implemented upon that dna cleaved the bonds bw the sugars and the nitrogenous bases composing the dna, releasing the individual bases from the dna strands The mixture of bases that had separated from their dna strands due to treatment with strong acid that cleaved the bonds bw sugars and nitrogenous bases, releasing the bases from their dna strands, these bases were then subjected to paper chromatography The mixture of bases was then subjected to paper chromatography in order to separate the four types of bases from one another The mixture of bases collected was then subject to paper chromatography in order to separate the four types of bases from one another An analysis of the base composition of DNA in different organisms may reveal important features about the structure of dna An analysis of the base compositions of dna in different organisms may reveal important features about the structure of dna, that was the goal of the experiment to reveal important features about the structure of dna through the analysis of base composition The starting material: the following types of cell were obtained: Escherichia coli, Streptococcus pneumoniae, yeast, turtle red blood cells, salmon sperm cells, chicken red blood cells, and human liver cells With the subjectification of the mixture of bases to chromatography in order to separate the bases from one another and identify them, this is what occurred: The bands were the results of the chromatography implementation Each base will absorb light at a particular wavelength, therefore spectroscopy was utilized in order to determine the amounts of each base The results, the data The data shown was only a small mapping of the results that Chargaff gleaned from his implemented experiments During the late 1940s and the early 1950s, Chargaff published many papers that were specifically concerned with the chemical composition of dna from biological sources Chargaff published many papers that were specifically concerned with the chemical composition of dna from biological sources Hundreds of measurements were made by chargaff were made Hundreds of measurements were made by chargaff were made Hundreds of measurements were made by chargaff The compelling observation was that the amount of adenine was similar to the amount of thymine and the amount of guanine was similar to the amount of cytosine The idea that the amount of A in DNA equals the amount of T, and that the amount of G equals C is known as Chargaff's rule These results of Chargaff's implemented experiments were not sufficient to propse a model for the structure of DNA However they provided the important clue that DNA is structured so that each molecule of adenine interacts with thymine and each molecule of guanine acts with cytosine A dna structure in which the nitrogenous base adenine binds to thymine and the nitrogenous base guanine binds to cytosine, would explain the equal amounts of A and T and equal amounts of G and C observed in Chargaff's experiments This observation made through the experiments of Chargaff, by Chargaff, became crucial evidence that Watson and Crick utilized in order to properly elucidate the structure of the double helix of dna

DNA supercoiling

DNA IS A LONG THIN MOLECULE DNA IS A LONG THIN MOLECULE DNA IS A LONG THIN MOLECULE bc Dna is a long thing molecule, twisting forces can dramatically impact and change dna conformation dna conformation can be dramatically impacted by twisting forces THE EFFECT IS SIMILAR AND COMPARABLE TO THE TWISTING OF A RUBBER BAND the effect of supercoiling, the twisting forces being exerted on dna and causing dramatic changes in dna conformation is comparable to the twisting of a rubber band if a rubber band is twisted none direction, the rubber band eventually coils itself into a v small, compact structure if a rubber band is coiled and twisted in a particular direction, consistently, it will lessen in the amount of space that it takes up, it will compact due to the consistent turning the rubber band that is being twisted will absorb the energy being applied by the implemented twisting motion, and therefore will compact itself and take up less space and become smaller in size technically, due to the absorption of energy given by the twisting action the two strands within DNA naturally coil around one another DNA is a double stranded molecule the two strands of DNA naturally coil around one another therefore, the formation of additional coils, further coiling and changes to the conformation of DNA due to further coiling is designated as supercoiling, DNA supercoiling is referred to as the formation of additional DNA coils, and changes in DNA conformation due to twisting forces being exerted on the DNA strand, causing changes and additional coils to the conformation of the DNA besides the natural coil it has being a double stranded molecule how do twisting forces exerted on DNA affect DNA structure, and cause a change in conformation of the DNA there are four possibilities as to how twisting forces exerted on DNA affect DNA structure, and how exertion of twisting forces can affect DNA structure 1) in figure 10.7a there is a double stranded DNA molecule THERE IS A DOUBLE STRANDED DNA MOLECULE THIS double stranded dna molecule has five complete turns this double stranded dna molecule has 5 complete turns this double stranded dna molecule is anchored bw two plates IN THIS HYPOTHETICAL EXAMPLE WHERE THERE IS A DOUBLE STRANDED DNA MOLECULE WITH 5 complete turns and it is anchored bw two plates, the DNA molecule with 5 complete turns that is also anchored bw two plates is unable to moves it cannot and is not able to rotate freely due to having 5 complete turns and being anchored bw two plates there can be underwinding and overwinding of DNA THERE CAN BE UNDERWINDING AND OVERWINDING OF DNA this underwinding or overwinding of dna can induce SUPERCOILING OF THE HELIX underwinding or overwinding of the DNA DOUBLE HELIX CAN INDUCE SUPERCOILING OF THE DOUBLE HELIX it can cause supercoiling of the double helix to occur, underwinding or overwinding if you look at B DNA, it is in a right handed helix the B DNA is in a right handed helix underwinding of this B DNA in a right handed helix would occur and come about due to a left handed twisting motion overwinding in this DNA molecule would come about due to a right handed twist so this B DNA is in a right handed helix overwinding will come about due to a right handed twist, a twist going in the same direction as the conformation of the B DNA underwinding will come about due to a left handed twist, a twist going in the opposite direction as the conformation of B DNA on the left side of the figure, one of the plates anchoring the DNA with 5 complete turns has been given a turn in the direction that winds to unwind, to undermined the helix the helix absorbs this unwinding force on it coming from one of the plates anchoring the DNA w 5 complete turns being turned in a direction promoting unwinding of the helix two things can happen THIS UNDERWINDING OF THE DNA HELIX can cause fewer turns to occur, figure 10.7 b or it can cause a NEGATIVE SUPERCOIL TO FORM figure 10.7c on the right handed side of figure 10.7, one of the plates that is securing the dna with 5 complete turns, 10 base pairs per turn, is turn in the right direction one of the plates anchoring the DNA in place is turned in the right direction, the same direction as the conformation of the DNA itself therefore overwinding the phenomenon of overwinding occurs, where the DNA is turned in the direction of its confirmation two things can occur in this situation the DNA can end up in a conformation with more turns, 1 more turn than 5 turns, so 6 turns, and fewer base pairs per turn another possibility is the formation of a positive supercoil, a positive supercoil can form in the DNA THESE DIFFERING DNA CONFORMATIONS of either a negative supercoil (due to a base plate being turned in a left handed direction, a left handed confirmation that goes in the opposite direction of the right handed conformation of the DNA, causing underwinding to occur), a positive supercoil (due to a base plate being turned in a right handed direction, a right handed conformation aligning with the right handed conformation of the DNA), and the original DNA conformation, the DNA with a right-handed conformation not being turned in either direction, being anchored bw two plates and have 5 complete turns, 10 base pairs per turn, THESE ARE ALL REFERRED TO AS TOPOISOMERS OF ONE ANOTHER the DNA confirmations that are shown in 10.7b and 10.7d, the structure where a left handed turn, the opposite of the DNA's right handed conformation occurs, causing underwinding, causing the DNA to make fewer turns, with more base pairs, about 12.5 base pairs per turn with 4 complete turns, as well as the structure where a right handed turn, one matching the conformation of the DNA< a right handed conformation, causes the DNA to be overwound, resulting in a DNA structure with more turns, 6 turns instead of 5, and fewer base pairs per turn, about 8.3 base pairs per turn THESE ABOVE DNA CONFORMATIONS ARE V UNSTABLE NOT STRUCTURALLY FAVORABLE AND THEREFORE ARE NOT VIABLE you will not see these aforementioned past two DNA conformations within living cells, bc they are far too unstable and not viable the chromosomal DNA in living bacteria IS NEGATIVELY SUPERCOILED the chromosomal DNA found in living bacteria is negatively supercoiled

chromosomal duplications

DUPLICATIONS TEND TO BE LESS HARMFUL THAN DELETIONS duplications of chromosomal segment, duplications of genetic material tend to be on the whole less harmful than deletions of chromosomal segments and deletions of genetic sequences DUPLICATIONS RESULT IN EXTRA GENETIC MATERIAL duplications are usually caused by abnormal events that occur during recombination duplications are usually caused BY ABNORMAL EVENTS THAT OCCUR DURING RECOMBINATION BW HOMOLOGOUS CHROMOSOMES THAT HAVE FORMED A SYNAPSE duplications result in extra, excess genetic material, and occur due to abnormal events during genetic recombination bw two homologous chromosomes that have formed a synapse during meiosis UNDER NORMAL CIRCUMSTANCES, CROSSING OVER OCURS AT ANALAGOUS SITES BW HOMOLOGOUS CHROMOSOMES, usually crossing over occurs bw homologous regions of homologous chromosomes, which will result in simple genetic variation however there may be an instance where a crossover can occur bw non-analogous, non homologous regions of homologous chromosomes crossing over can occur AT MISALIGNED SITES ON THE HOMOLOGS the homologs can be misaligned, where these chromosomes are homologs, where they are a pair of homologous chromosomes, but they are misaligned, where their homologous regions do not line up properly, and therefore recombination and crossing over occurs bw misaligned and therefore non homologous regions of the chromosomes WHAT CAUSES THE MISALIGNMENT what causes the misalignment of these homologous chromosomes that causes crossing over and genetic recombination bw misaligned, nonhomologous regions of the two chromosomes in some cases, A CHROMOSOME MAY CARRY TWO OR MORE HOMOLOGOUS SEGMENTS OF DNA THAT HAVE IDENTICAL OR HAVE V SIMILAR SEQUENCES chromosomes may carry two or more homologous segments/sections of dna that have identical or v similar sequences chromosomes may carry two or more homologous segments/sections of DNA that have identical or similar sequences THESE ARE CALLED REPETITIVE SEQUENCES these are called repetitive sequences BECAUSE THESE SEQUENCES OCCUR A MULTITUDE OF TIMES they are designated as repetitive sequences bc these sequences occur a multitude of times an example of repetitive sequences- TRANSPOSABLE ELEMENTS an example of repetitive sequences- TRANSPOSABLE ELEMENTS are elements that can move throughout the genome repetitive sequences can align with each other an example of this misaligned crossover: the REPETITIVE SEQUENCE ON THE RIGHT (IN THE UPPER CHROMATID) has lined up with the SAME REPETITIVE SEQUENCE ON THE LEFT ON THE LOWER CHROMATID the alignment should not occur this way, because the upper chromatid on one chromosome is aligning with the lower chromatid on the left chromosome, which is a misalignment (upper should align with upper, lower should align with lower) , but they are aligning bc they both have this repetitive sequence, and the repetitive sequences are recognizing one another as homologous and therefore align themselves without considering the rest of their respective chromosomes and the appropriate alignment of the rest of the chromatids composing these chromosomes a crossover bw these misaligned chromosomes then occurs THIS IS DESIGNATED AS NONALLELIC HOMOLOGOUS RECOMBINATION it is designated as non allelic homologous recombination, bc the recombination and crossing over is taking place at homologous sites, bw the two homologous repetitive sequences that recognized one another and caused the chromosomes to align accordingly however, the alleles of the neighboring genes, the genes around these repetitive sequences, are not homologous and are not appropriately aligned THEREFORE ONE CHROMATID HAS AN INTERNAL DUPLICATION THE OTHER CHROMATID HAS A DELETION a misaligned crossover results in one chromatid having an internal duplication, and the another chromatid having a deletion in the shown figure, the CHROMOSOME WITH THE INTERNAL DUPLICATION, WITH THE EXTRA GENETIC MATERIAL, has a gene duplication the chromosome with the extra genetic material, the chromatid containing the extra genetic material helping to compose a chromosome has A GENE DUPLICATION, 2 copies of gene C in the majority of cases, GENE DUPLICATIONS OCCUR AS RARE AND SPORADIC EVENTS gene duplications in the majority of cases occur as rare and sporadic events during the EVOLUTION OF SPECIES we will later investigate how MULTIPLE COPIES OF GENES CAN EVOLVE INTO A FAMILY OF GENES, with each individual gene having a specified function we will later investigate how multiple copies of genes can evolve into a family of genes, with each gene within this created gene family having a specific function, a specific responsibility, and this gene family having been created due to gene duplications and the resulting presence of copies of multiple genes LIKE DELETIONS THE PHENOTYPIC CONSEQUENCE OF DUPLICATIONS ARE ASSESSED ALONGSIDE THE SIZE OF THE DUPLICATION the phenotypic consequence of a duplication relies upon the size of the gene duplication, that will influence the degree of the phenotypic consequence the phenotypic consequence of duplications correlates to the size of the duplication DUPLICATIONS ARE MORE LIKELY TO HAVE PHENOTYPIC CONSEQUENCES IF THEY INVOLVE A LARGE PIECE OF THE CHROMOSOME if a large chromosomal segment is duplicated, then duplications are more likely to have more dramatic phenotypic consequences IN GENERAL SMALLER DUPLICATIONS ARE LESS LIKELY TO HAVE HARMFUL EFFECTS in general, smaller duplications are less likely to have harmful effects smaller duplications are less likely to have harmful effects duplications are more likely to have harmful effects if they are large duplications, if they involve a large chromosomal segment that is duplicated small duplications are less likely to have harmful effects and substantially effect the phenotype of the organism with the duplication, compared to the phenotype of an organism with a larger duplication of comparable size this observation, that small duplications, on the whole tend to be less harmful than larger duplications, indicates that HAVING ONLY ONE COPY OF A GENE is more harmful than having 3 copies HAVING ONLY ONE COPY OF A GENE IS MORE HARMFUL THAN HAVING THREE COPIES OF A GENE duplications tend to be less harmful than deletions in humans, there are RELATIVELY FEW WELL DEFIND SYNDROMES CAUSED BY SMALL CHROMOSOMAL DUPLICATIONS within humans, there are relatively few well defined syndromes that are caused by SMALL CHROMOSOMAL DUPLICATIONS there are relatively few well defined syndromes that are caused by small chromosomal duplications, there are a few well defined, well-known, and verified human syndromes caused by small chromosomal duplications an example of a human disease, a well defined syndrome caused by chromosomal duplication is CHARCOT-MARIE-TOOTH DISEASE (type 1A) there is Charcot-marie tooth disease Charcot-Marie tooth disease is a PERIPHERAL NEUROPATHY this PERIPHERAL NEUROPATHY IS CHARACTERIZED BY NUMBNESS IN THE HANDS AND FEET this peripheral neuropathy is CHARACTERIZED BY NUMBNESS IN THE HANDS AND FEET charcot-marie-tooth disease (type 1a) is a well-defined syndrome caused by a small chromosomal duplication, and it is a PERIPHERAL NEUROPATHY this well defined syndrome is characterized by NUMBNESS IN THE HANDS AND FEET this numbness in the hands and feet due to the peripheral neuropathy that defines charcot-marie-tooth disease is due to a small duplication on the short arm, the p arm of CHROMOSOME 17 IN CONTRAST TO THE SMALL GENE DUPLICATION OF THE SHORT ARM THE P ARM ON CHROMOSOME 17 THAT CAUSES CHARCOT-MARIE-TOOTH DISEASE, the majority of small chromosomal duplication have no phenotypic consequences and no phenotypic effect the majority of small chromosomal duplications have no phenotypic consequences and no phenotypic effects HOWEVER SMALL CHROMOSOMAL DUPLICATIONS ARE STILL VITALLY IMPORTANT despite having no phenotypic consequences bc THEY PROVIDE RAW MATERIAL FOR THE ADDITION OF MORE GENES INTO A SPECIES'S CHROMOSOMES small chromosomal duplications are still vitally important despite not having any phenotypic consequences bc they provide raw material for the introduction of more genes into a species's chromosome complement OVER THE COURSE OF MANY GENERATIONS and the introduction of a multitude of genes into the chromosome complement of an organism, THE FORMATION OF A GENE FAMILY CAN OCCUR this gene family consists of TWO OR MORE GENES THAT ARE SIMILAR TO ONE ANOTHER THIS GENE FAMILY CONSISTS OF TWO OR MORE GENES THAT ARE SIMILAR TO ONE ANOTHER a gene family consists of two or more genes that are similar to one another the MEMBERS OF A GENE FAMILY ARE DERIVED FROM THE SAME ANCESTRAL GENE the member of a gene family descend from the same ancestral gene a gene family consists of two or more genes that are similar to one another, therefore belong to the same gene family, and these genes in a gene family are derived from the same ancestral gene OVER TIME TWO COPIES OF AN ANCESTRAL GENE CAN ACCUMULATE DIFFERENT MUTATIONS that causes variation bw the two of them therefore, after many generations, where the propagation of two variegated and somewhat different genes descending from the same ancestral gene has occurred, the TWO GENES WILL BE SIMILAR YET NOT IDENTICAL AND WILL THEREFORE BELONG TO A GENE FAMILY due to the creation of two copies of an ancestral gene that accumulated separate mutations, and the maintenance of these mutations throughout generations, results in two genes THAT ARE SIMILAR BUT NOT IDENTICAL they both descend from the same ancestral gene, but have different mutations that make them distinct from one another DURING EVOLUTION. this type of event the accumulation of genetic mutations in two copies of an ancestral gene can occur several times, thus resulting in the creation of several SIMILAR BUT NOT IDENTICAL GENES that belong to the same family due to them all descend from the same ancestral gene WHEN TWO OR MORE GENES ARE DERIVED FROM A SINGLE ANCESTRAL GENE, the genes are said to be HOMOLOGOUS TO ONE ANOTHER when two or more genes are DERIVED FROM A SINGLE ANCESTRAL GENE, the genes are said to be homologous to one another HOMOLOGOUS GENES WITHIN A SINGLE SPECIES ARE KNOWN AS PARALOGS homologous genes within a single species, two or more genes that have descended from the same ancestral gene that are found within a single species are designated as paralogs when there are two or more genes that descend from the same ancestral gene, they are designated as homologous to one another, they are known as homologs of one another when there are two or genes that have descended from the same ancestral gene that are found within a single species, they are designated as PARALOGS, and they constitute a gene family, of genes that descend from the same ancestral gene, ARE SIMILAR BUT NOT IDENTICAL, and are found within a single species

nucleic acid structure

Dna and its molecular cousin, RNA are both known as nucleic acids DNA and its molecular cousin RNA are both designated as nucleic acids DNA and its molecular cousin RNA are both designated as nucleic acids DNA and its molecular cousin RNA are both designated as nucleic acid This term is derived from the discovery of DNA by Friedrich Miescher in 1869 Friedrich Miescher discovered DNA in 1869 He identified a novel phosphorus containing substance from the nuclei of white blood cells Friedrich Miescher discovered DNA in 1869 He identified a novel phosphorus containing substance from the nuclei of white blood cells From the nuclei of white blood cells he identified a substance containing phosphorus within the nuclei of white blood cells From the nuclei of white blood cells he identified a substance containing phosphorus within the nuclei of white blood cells From the nuclei of white blood cells he identified a substance containing phosphorus within the nuclei of white blood cells He found white blood cells within waste surgical bandages Within waste surgical bandages there were white blood cells and this scientist took these white blood cells from the waste surgical bandages and investigated and analyzed these white blood cells Within the nuclei of these white blood cells that he found within waste surgical bandages, within the nuclei of these white blood cells, he found a phosphorus containing substance within the nuclei of these white blood cells He named this phosphorus containing substance within the nuclei of white blood cells nuclein As the structure of DNA and RNA became better understood, it was found that they are acidic molecules As the structure of DNA and RNA became better understood, and the parameters of these types of genetic material were fleshed out, it was found that DNA and RNA are both acid molecules, which is why they are designated as nucleic acids, found within the nucleus of eukaryotic cells or the nucleoid region of prokaryotic cells, and are acidic How was it determined that DNA and RNA are acidic, they release hydrogen ions in solution, which turn something more acidic, the release of hydrogen ions in solution, and they have a net negative charge at neutral ph so even when everything around them is at neutral ph, DNA and RNA both maintain an acid ph, a net negative charge at neutral ph Therefore the term nucleic acid was coined in order to designate DNA and RNA as nucleic acids Geneticists, biochemists, and biophysicists have been interested in the molecular structure of nucleic acids for several decades Both rna and dna are macromolecules composed of smaller building blocks To fully appreciate their structures, to fully appreciate the structures of RNA and DNA< these macromolecules composed of smaller building blocks, we need to understand the four levels of complexity for these molecules, for RNA and DNA designated as nucleic acids 1. Nucleotides form the repeating structural unit of nucleic acid Nucleotides form the repeating structural unit of nucleic acid Nucleotdies form the repeating structural unit of nucleic acid Nucleotides form the repeating structural unit of nucleic acids 2. Nucleotides are linked together in a linear manner Nucleotides are linked together wtith one another in a linear manner in order to form a single strand of DNA or RNA Nucleotides are linked together with one another in a linear manner in order to form a single strand of DNA or RNA Nucleotides are linked together with one another in a linear manner in order to form a single strand of DNA or RNA Nucleotides are linked together with one another in a linear manner in order to form a single strand of DNA or RNA Nucleotides are linked together with one another in a linear manner in order to form a single strand of DNA or RNA 3. Two strands of dna, and sometimes two strands of Rna interact with one another in order to form a double helix Always two strands of dna interact with one another in order to form a double helix Always two strands of dna interact with one another in order to form a double helix Always two strands of dna interact with one another in order to form a double helix The 3 dimensional structure of DNA results from the folding and bending of the double helix The 3 dimensional structure of DNA results from the folding and bending of the double helix The 3 dimensional structure of DNA results from the folding and bending of the double helix The 3 dimensional structure of DNA results from the folding and bending of the double helix formed by the interation that occurs bw two strands of dna each individually formed by the arrangement of nucleotides in a linear manner Within living cells, DNA is associated with a variety of proteins that influence its structure

triplex dna

Dna can form a triple helix Dna can form a triple helix, and this triple helix forming dna is known as triplex dna is designated as triplex dna There was a surprising discovery made in 1957 by Alexander Rich There was a surprising discovery made in 1957 by Alexander Rich, David Davies, and Gary Felsenfield This suprising discovery was that DNA is able to form a triple helical structure Dna is able to form a triple helical structure This triple helical structure is called triplex dna This triplex was formed in vitro using pieces of dna that were made synthetically This triple helical structure is known as triplex dna, and this triplex dna was formed synthetically, utilizing small pieces of synthetically produced dna in vitro Although the result was intriguing, it did not appear to have biological significance However, today there is increased and vested interest in triplex dna This interest in triplex dna was renewed by the observation that triplex dna can from in vitro by mixing both natural stranded double helix dna, natural double stranded dna and a third short strand of dna that is synthetically produce The synthetic strand while in vitro binds into the major groove of the naturally occurring double stranded dna The short synthetically produced strand of dna binds into the major groove of the naturally occurring double stranded dna The short synthetically produced strand of dna binds into the major groove of the naturally occurring double stranded dna, it binds into the major groove of the naturally occurring double stranded dna An interesting feature of the formation and creation of triplex dna is that it is sequence specific In other words, the synthetic and short third strand incorporates itself into a tyiple helix The synthetic and short strand of DNA the short and synthetically made strand of DNA incorporates itself into a triple helix How does this synthetic short strand of dna incorporate itself into a triple helix How does this synthetic short strand of dna incorporate itself into a triple helix How does this synthetic short strand of dna incorporate itself into a triple helix This synthetically made and short strand of dna incorporates itself into the triple helix due to specific interactions occurring bw the synthetic short strand of dna and the two strands of biological dna forming a helix that the synthetic short strand of dna is attempting to incorporate itself into The pairing rules are that a thymine in the synthetic short strand of dna, the nitrogenous base thymine in the synthetic short strand of dna hydrogen bonds to a nitrogenous base pair of adenine and thymine within the double helix formed by the two strands of biological dna The other pairing rule is that a cytosine from the synthetically made short strand of dna hydrogen bonds to the nitrogenous base pair consisting of a cytosine and guanine within the double helix formed by the two strands of biological dna The formation of triplex dna has been implicated in several cellular processes The formation of triplex dna has been implicated in several cellular processes The formation of triplex dna has been implicated in several cellular processes The formation of triplex dna has been implicated in several cellular processes The formation of triplex dna has been implicated in several cellular processes The formation of triplex dna has been particularly indicated in the process of genetic recombination, a phenomenon that takes place during meiosis I, particularly during prophase I Researchers are interested in triplex dna due to the potential of triplex dna as a tool that can be utilized in order to specifically inhibit particular genes Researchers are v interested in triplex dna due to the potential of triplex dna as a tool that can be utilized in order to specifically inhibit particular genes, the potential to utilize triplex dna as a tool to specifically inhibit particular genes Researchers are particularly interested in the potential to utilize triplex dna in order to specifically inhibit particular genes The synthetic and short strand of dna binds into the major groove, the indentation in the double helix of the dna where atoms of the base pairs are in contact with the surrounding water, into the major groove of the double helix of dna that is formed by the two strands of biological dna, and this short and synthetic strand of dna binds into the major groove of the double helix formed by the two strands of biological stand while aligning with and following the specific pairing rules The short and synthetic strand of dna incorporates itself into the double helix formed by the two biological strands of dna by binding into the major groove of the double helix formed by the two biological strands of dna, the major groove being an indentation within the dna where atoms of the base pairs in this particular section have contact with the surrounding water The short and synthetic strand of dna binds into this groove of the double helix formed by the two biological strands of dna according to specific base pairing rules, perhaps the aforementioned rule of the thymine base of the short and synthetic dna strand hydrogen bonding to the nitrogenous base pair of adenine and thymine withint the double helix formed by the two biological strands, and the cytosine base within the short synthetic dna strand binding to the nitrogenous base pair of cytosine and guanine found within the double helix formed by the two biological strands Therefore researchers can design a synthetic dna to recognize the base sequence found within a specific gene due to the short synthetic dna strand binding into the major groove of the double helix formed by the two biological strands of dna according to specific and established base pairing rules Researchers can design a synthetic dna to recognize the base sequence found within a particular gene Researchers can design a synthetic dna to recognize the base sequence found within a particular gene When the synthetic dna when the short synthetic dna strand binds to a gene, due to it being designed to recognize the base sequence found within a specific gene, the base sequence encoding a specific gene, when the short synthetic strand of dna binds to that base sequence encoding that gene, it can inhibit transcription In addition to this ability, the synthetic dna can cause mutations within a gene The synthetic dna can cause a mutation within a gene The synthetic dna can cause mutations within a gene that inactivate the function of this gene The synthetic dna can cause mutations within a gene that inactivate the function of this gene Researchers are excited about the possibility of utilizing synthetic dna in order to silence the expression of particular genes For example, this approach of utilizing synthetic dna in order to inactivate the transcription and therefore function of a gene could be utilized in order to silence and inactivate the transcription and function of genes that become overactive within cancer cells This technology this utilization of the short synthetic dna strand could be applied to silencing the transcription and function of genes that are overactive within cancer cells However, further research is required in order to develop plausible and effective ways in order to promote the uptake of synthetic dna into the appropriate target cells, so far triplex dna has not been formed within living cells The technology needs to be further developed in order for the short synthetic strand to be taken up properly into living cells to simply inactivate the transcription and function of genes that the synthetic strand is programmed to inactive, programmed to inactivate by having the genetic sequence of the gene, the base sequence found in a particular gene recognized by this synthetic strand of dna, so it can find the sequence encoding a particular gene targeted for inactivation, recognize it, and then inactivate its transcription and therefore its function

alternate types of double helices

Dna can form alternative types of double helices Dna is able to form alternative types of double helices The dna double helix is able to form alternative types of double helices The dna double helix is able to form alternative types of double helices The dna double helix can form different types of structure s We can look at the structures of A DNA, B DNA, and Z DNA The highly detailed structures shown here, these were deduced by X-ray crystallography on short segments of dna The highly detailed structures showcased within the book were deduced and produced due to the implementation of x ray crystallography on short segments of dna B DNA IS THE PREDOMINANT FORM OF DNA FOUND WITHIN LIVING CELLS B DNA IS THE PREDOMINANT FORM OF DNA FOUND WITHIN LIVING CELLS B DNA is the predominant form of dna found within living cells B dna is the predominant form of dna that is found within living cells However, understand certain particular in vitro conditions, the two strands of dna are able to twist into A DNA or Z DNA, and these types of DNA, A DNA or Z DNA differ significantly from B DNA These types of DNA, A DNA OR Z DNA differ substantially and significantly from b dna, and the two strands of dna forming b dna, the most common form of dna the majority form of dna found within living cells, under a particular set of in vitro conditions, the two strands forming the double helix can twist into A DNA or Z DNA A and B DNA are both right handed helices with a right handed conformation Z DNA has a left handed confirmation Z DNA has a left handed fcofnormation In addition to this, the helical backbone in Z dna appears to zig zag slightly as the Z dna backbone winds itself around the double helical structure The helical backbone in Z dna appears to zig zag slightly as the Z dna backbone winds itself around the double helical structure This might be a good way to remember z dna z dna zig zag the backbone of z dna winds itself in a somewhat zig zag pattern around the double helical structure, and the Z dna is unique in that it has a left handed conformation A and B dna both have a right handed conformation The number of base pairs per 360 degree turn in A dna, with a right handed conformation, is 11 base pairs per turn The number of base pairs per 360 degree turn in B dna, with a right handed conformation, and recall that B dna is the most common and predominant form of dna found within living cells, this is 10 base pairs per 360 degree turn The number of base pairs per 360 turn in Z dna, with a left handed conformation and the backbone winding in a zig zag pattern around the double helical structure, is 12 base pairs per 360 turn In b dna, the bases tend to be centrally located In b dna the most predominant form of dna found within living cells, the bases tend to be centrally located, and the hydrogen bonds that occur bw the bases forming the base pairs occur relatively perpendicular to the central axis In contrast to this orientation of the bases in base pairs of b dna, within a dna and z dna, the bases forming base pairs are substantially tilted relative to the central axis of the double helix The ability of the predominant B DNA to adopt A-DNA and Z DNA conformations Recall that the number of base pairs per 360 turn of A DNA is 11 base pairs, and is in a right handed conformation The number of base pairs per 360 degree turn of Z DNA is 12 base pairs, and is in a left handed conformation, and the backbone of z dna winds in a zig zag pattern around the double helical shape The ability of the predominant B dna to adopt the conformations of A DNA and Z DNA is dependent upon particular conditions In conducted x ray diffraction studies, A DNA occurs under conditions of lower humidity In x ray diffraction studies, A DNA occurs under conditions of lower humidity The ability of a double helix to adopt a z dna conformation depends on a variety of factors At high ionic strength, at a high salt concentration, the formation of a Z DNA conformation is favored by a sequence of bases that alternates bw purines (the 2 ring structures, adenine and guanine) and pyrimidines (the single ring structure, cytosine and thymine) At lower ionic strength or at a lower salt concentration, the methylation of cytosine bases can potentially favor Z dna conformation So at high ionic strength, the dna sequences containing alternating purines and pyrimidines will favor a Z dna concentration And at low ionic strength, low ionic concentration, low salt concentration for example, the methylation of cytosine bases can favor Z DNA conformation When does cytosine methylation occur Cytosine methylation occurs when there is a cellular enzyme This cellular enzyme attaches a methyl group, a CH3 group to the cytosine base Negative supercoiling also favors the z dna conformation, where in a 360 degree turn of the double helix (where the base pairs are tilted in regards to the central axis and the backbone winds in a zig zag pattern around the double helical shape) there are 12 bp per turn What is the biological significance of A and Z DNA? What is the biological significance of A and Z dna The biological significane Research has not yet found a biological reason or biological role for A dna in particular However, there is accumulating collected evidence indicating that there is ineed a possible biological role for Z DNA in regards to the process of transcription There is accumulating collected evidence indicating that there is indeed a possible biological role for Z DNA in regards to the process of transcription, Z DNA may be important to the process of transcription There has been recent research implemented, and this recent research has identified cellular proteins, these cellular proteins specifically recognize Z DNA These cellular proteins specifically recognize Z DNA In 2005, Alexander Rich and his colleagues reported that the Z DNA binding region of one such protein that specifically recognizes Z DNA, the Z dna binding region of one such protein the region of the protein that binded dna played a role in regards to regulating the transcription of particular genes Regulating the transcription of particular genes In addition, there has been other research done that has suggested that perhaps Z dna may play a role in regards to chromosome structure and the level of compactions of chromosomes

eukaryotic chromosome structure

EACH EUKARYOTIC CHROMOSOME contains a LONG LINEAR DNA MOLECULE within every eukaryotic chromosome, there is a long and linear dna molecule, a dna molecule that is lengthy as well as linear in shape (in contrast to the circular shape of a bacterial chromosome) THERE ARE 3 TYPES OF REGIONS THAT ARE REQUIRED FOR BOTH CHROMOSOMAL REPLICATION AND SEGREGATION there are 3 types of chromosomal regions that are necessary for chromosomal replication during a synthesis phase prior to mitosis or meiosis i as well as chromosome segregation during anaphase of mitosis, anaphase I or anaphase ii of meiosis to occur these three regions are: ORIGINS OF REPLICATION CENTROMERES TELOMERES these three regions of chromosomes that are necessary for chromosomal replication and segregation to occur are ORIGINS OF REPLICATION CENTROMERES AND TELOMERES ORIGINS OF REPLICATION these are particular regions on a chromosome that are required in order to initiate the process of DNA replication origins of replication are particular regions on a chromosome that are required in order to initiate DNA replication bacterial chromosomes each have one a single origin of replication and no more than that eukaryotic chromosomes, in contrast to bacterial chromosomes (which contain a single origin of replication), contain many origins of replication eukaryotic chromosomes contain a multitude of origins of replication these multiple origins of replication are spaced about 100,000 base pairs apart these multiple origins of replication on eukaryotic chromosomes are spaced about 100,000 BASE PAIRS APART ALONG THE CHROMOSOME what are centromeres? centromeres are regions that play a role in the PROPER SEGREGATION OF CHROMOSOMES centromeres are regions that play a role in the PROPER SEGREGATION OF CHROMOSOMES centromeres are regions on chromosomes that play a role in chromosome segregation, the chromosomal segregation that occurs during anaphase of mitosis, and anaphase II of meiosis for the majority of eukaryotic species, within the majority of eukaryotic species, each one of an individual's eukaryotic chromosomes contains a single centromere a centromere within a eukaryotic chromosome presents as such: A CONSTRICTED REGION OF A MITOTIC CHROMOSOME a centromere within a eukaryotic chromosome presents as a CONSTRICTED REGION OF A MITOTIC CHROMOSOME a region of a mitotic chromosome, a chromosome that is capable of undergoing mitosis, that is constricted CENTROMERES function as a site for kinetochores synthesis, kinetochore formation centromeres serve as a site for kinetochore formation to occur centromeres serve as constricted regions of mitotic chromosomes that serve as sites for kinetochore formation KINETOCHORES ASSEMBLE JUST BEFORE AS WELL DURING THE EARLY STAGES OF MITOSIS AND MEIOSIS kinetochores assemble just prior to as well as during the early stages and phases of mitosis and meiosis, and they know where to assemble based on the location of the centromere they are formed at the location of the centromere and are ultimately located just by or near the centromere what is the kinetochore composed of? the kinetochore is composed of A GROUP OF CELLULAR PROTEINS the kinetochore is composed of a group of cellular proteins these cellular proteins that a kinetochore is composed of LINK THE CENTROMERE TO THE SPINDLE APPARATUS DURING THE PROCESSES OF MITOSIS AND MEIOSIS during the processes of mitosis and meiosis the cellular proteins composing the kinetochores that are located right by/near the centromeres (and are assembled at the location of the centromeres, kinetochores composed of a group of cellular proteins are assembled at the locations of centromeres, and then settle on the chromosome right by the centromeres) are responsible for linking the centromere to the spindle apparatus the cellular proteins that compose kinetochores are responsible for securing the centromeres to the spindle apparatus during the processes of mitosis and meiosis, ensuring proper chromosomal segregation occurs during these processes the cellular proteins that compose kinetochores are responsible for securing the centromeres of chromosomes to the spindle apparatus during the processes of mitosis and meiosis in order to ensure that proper chromosomal segregation occurs, and the daughter cells or gametes formed by the aforementioned processes are allocated the correct amount of genetic material there are particular species such as saccharomyces cerevisiae, a particular yeast species within this particular yeast species saccharomyces cerevisiae, THE CENTROMERES OF THIS PARTICULAR YEAST SPECIES have a DEFINED DNA sequence the centromeres of this particular yeast species saccharomyces cervisiae have a DEFINED DNA sequence OF 125 BASE PAIRS IN LENGTH the centromeres of this particular yeast species saccharomyces cerevisiae are 125 base pairs in length, this is the length of the centromeres of this particular yeast species THIS TYPE OF CENTROMERE with a specified and outlined and established base pair length, (recall that the centromeres within the particular yeast species saccharomyces cerevisiae are specifically 125 base pairs in length) is designated as a POINT CENTROMERE in comparison to these point centromeres with specified base pair lengths, there are centromeres found in far more complex eukaryotes these centromeres found in more complex eukaryotic organisms are MUCH LARGER these much larger sequences also contain a multitude of tandemly repeated DNA sequences these much larger sequences DNA sequences composing the centromeres of more complex eukaryotic organisms contain a multitude of copies of tandemly repeated DNA sequences THESE CENTROMERES In more complex eukaryotic organisms, being much larger in size in regards to the amount of DNA and the length of their DNA sequence, as well as containing a multitude of copies of tandem repeats, are designated as REGIONAL CENTROMERS REGIONAL CENTROMERES can range in size from SEVERAL THOUSAND BASE PAIRS IN LENGTH to OVER A MILLION BASE PAIRS IN LENGTH the repeated DNA sequences, the copies of repeated dna sequences found within regional chromosomes are not necessary or sufficient enough to form a functional centromere as well as a kinetochore these repeated DNA sequences, these copies of repeated DNA sequences found within regional centromeres are not considered necessary or sufficient on their own to form centromeres and kinetochores THERE ARE OTHER BIOCHEMICAL PROPERTIES THAT ARE REQUIRED IN ORDER TO PROPERLY PRODUCE A FUNCTIONAL CENTROMERE AND KINETOCHORE there are other biochemical properties necessary for the proper formation of centromeres and kinetochores recall that there are other biochemical properties required to properly form centromeres and their respective kinetochores there is a distinctive feature of ALL EUKARYOTIC CENTROMERES there is a distinctive biochemical feature of all eukaryotic centromeres every eukaryotic centromere created that is required in order for the proper formation of centromeres and their respective kinetochores to occur this biochemical feature of all eukaryotic chromosomes is that histone H3, this histone is replaced with a histone variant designated as CENP-A researchers are currently still trying to identify all of the biochemical features that are unique to regional chromosomes and required for the proper formation of centromeres and their respective kinetochores, and they are also still trying to comprehend how these particular biochemical features are transmitted to new cells during the process of cellular division what are telomeres? the ENDS OF LINEAR CHROMOSOMES there are specialized regions at the end of LINEAR CHROMOSOMES THAT ARE DESIGNATED AS TELOMERES there are specialized regions at the end of linear chromosomes that are designated as telomeres- these are specialized regions at the end of linear chromosomes that are designated as telomeres what are the important integral functions of telomeres that are responsible for/contribute to the successful replication and/or segregation of chromosomes during mitosis and meiosis telmores have several important functions that all contribute to the replication and stability of a given chromosome TELOMERES CONTRIBUTE TO THE REPLICATION AND STABILITY OF A GIVEN CHROMOSOME recall the professor in your lecture on Friday who talked about how telomeres hold chromosomes together, and unraveling, weakened telomeres are thought to be signs of aging TELOMERES serving as specialized regions at the ends of chromosomes PREVENT CHROMOSOMAL REARRANGEMENTS telomeres serving as specialized regions at the end of chromosomes prevent chromosomal rearrangements an example of chromosomal rearrangement would be translocations telomeres are preventative of chromosomal rearrangements such as translocations TELOMERES ALSO PREVENT CHROMOSOME SHORTENING in two ways telomeres prevent chromosome shortening in two ways the telomeres protect chromosomes from digestion via enzymes designated s exonuclease THE TELOMERES PROTECT CHROMOSOMES FROM DIGESTION THAT WOULD OCCUR TO THESE CHROMOSOMES DUE TO THE FUNCTION OF EXONUCLEASES THAT ARE REPSONSIBLE FOR DIGESTING CHROMOSOMES exonuclease enzymes are able to recognize the ends of DNA, and after recognizing the ends of the DNA, nucleases are able to digest chromosomes the telomeres prevent these exonuclease from being able to identify the ends of chromosomes, and therefore prevent these exonuclease from being able to digest the chromosomes that they serve as specialized end regions on there is a second way in which telomeres prevent chromosomal shortening recall that the first way they prevent chromosomal shortening is by preventing the function of exonuclease, enzymes that recognize the DNA sequences at the ends of chromosomes and proceed to digest them the telomeres stop the exonuclease from being able to recognize the ends of chromosomes, and therefore also stop the exonuclease from being able to digest the chromosomes the second way that telomeres go about preventing the shortening of chromosomes AN UNUSUAL FORM OF DNA REPLICATION may occur at the telomere this unusual form of dna replication may occur at the telomere in the telomeric region, in order to ensure that the EUKARYOTIC CHROMOSOMES do not become shortened with a multitude of rounds of DNA replication an unusual form of DNA replication may occur at the telomeres in order to prevent the shortening of eukaryotic chromosomes whenever a round of dna replication occurs there are genes located BW the centromeric and telomeric regions, genes that span along the entirety of the length of the eukaryotic chromosome A SINGLE CHROMOSOME usually contains about a few hundred to SEVERAL THOUSAND GENES the sequence of a typical eukaryotic gene (recall that typically, a eukaryotic chromosome will contain a few hundred to several thousand genes) will be around several thousand to tens of thousands of base pairs in length a given gene out of those few hundred to several thousand genes located on a single eukaryotic chromosome will contain several thousand to TENS OF THOUSANDS OF BASE PAIRS a given gene in the few hundred to several thousand genes on a single linear eukaryotic chromosome will have lengths of several thousand to tens of thousands of base pairs in less complex eukaryotes such as yeast, the genes tend to remain small these relatively smaller genes with shorter lengths and less base pairs tend to PRIMARILY CONTAIN NUCLEOTIDE SEQUENCES THAT ENCODE THE AMINO ACID SEQUENCES WITHIN PROTEINS these relatively smaller genes within the chromosomes of less complex eukaryotes such as yeast tend to primarily contain SEQUENCES THAT ENCODE THE AMINO ACID SEQUENCES FOUND WITHIN PROTEINS within less complex eukaryotes their genes will contain nucleotide sequences coding for the amino acid sequences found within protein in more complex eukaryotic organisms more complex eukaryotic organisms would be considered mammals and flowering plants mammals and flowering plants are considered more complex eukaryotic organisms in these more complex eukaryotic organisms such as mammals and flowering plants, THERE ARE STRUCTURAL GENES and these structural genes tend to be much longer DNA sequence wise due to the presence of INTRONS INTRONS ARE NONCODING INTERVENING SEQUENCES INTRONS are noncoding intervening sequences introns are noncoding intervening sequences of dna they do not code for anything and rather serve as interventions along a sequence of DNA they serve the purpose, in more complex eukaryotic organisms such as mammals and flowering plants, of lengthening the DNA sequences of structural genes INTRONS RANGE IN SIZE introns range in size as noncoding intervening sequences from less than 100 base pairs to MORE THAN 10,000 base PAIRS less than 100 base pairs to more than 10,000 base pairs introns can range in length from 100 to more than 100,000 base pairs recall that introns are noncoding intervening sequences of dna that are responsible in more complex eukaryotic organisms for lengthening the DNA sequences composing their structural genes THE PRESENCE OF LARGE INTRONS can have a dramatic affect on the length of structural genes in more complex eukaryotes, greatly lengthening these DNA sequences

eukaryotic chromatin

EUKARYOTIC CHROMATIN MUST BE COMPACTED IN ORDER TO FIT WITHIN A LIVING CELL EUKARYOTIC CHROMATIN MUST BE COMPACTED IN ORDER TO FIT WITHIN A LIVING CELL eukaryotic chromosomes are therefore folded in order to fit within a living cell eukaryotic chromosomes cannot fit within a living cell without being compacted first A TYPICAL EUKARYOTIC CHROMOSOME looking at a typical eukaryotic chromosome, a typical eukaryotic chromosome contains a SINGLE LINEAR DOUBLE STRANDED DNA MOLECULE a typical eukaryotic chromosome consists of a SINGLE LINEAR DOUBLE STRANDED DNA MOLECULE the dna molecule that a single eukaryotic chromosome consists of a is a SINGLE LINEAR DOUBLE STRANDED DNA MOLECULE this single, linear, double stranded dna molecule may be HUNDREDS OF MILLIONS OF BASE PAIRS IN LENGTH this single linear double stranded dna molecule that constitutes a single eukaryotic chromosome can be HUNDREDS OF MILLIONS OF BASE PAIRS IN LENGTH if the dna from a single set of human chromosomes was stretch from end to end the length of this dna would be OVER 1 METER if the dna from a single set of chromosomes was taken out of the nucleus and stretched from end to end, the length of the dna composing this single set of chromosomes would be OVER A METER IN LENGTH THE MAJORITY OF EUKARYOTIC CELLS ARE ONLY ABOUT 10 TO 100 MICROMETERS IN DIAMETER the cell nucleus is only about 2 to 4 MICROMETERS IN DIAMETER the diameter of the avg eukaryotic cell as well as the diameter of the cell nucleus, both of these are far too small to accommodate the length of DNA THEREFORE THE DNA within a eukaryotic cell must be folded and packaged by a dramatic staggering amount in order for this DNA to fit within the nucleus how is the appropriate compaction of the linear DNA found within eukaryotic chromosomes accomplished? what mechanisms are utilized in order to appropriately compact the eukaryotic dna enough for it to fit inside of the eukaryotic nucleus which is 2 to 4 micrometers in diameter and the eukaryotic cell which is 10 to 100 micrometers in diameter this compaction and folding and packaging of eukaryotic dna in order for it to fit into the eukaryotic nucleus 2 to 4 micrometers in diameter and the eukaryotic cell itself 10 to 100 micrometers in diameter is accomplished through mechanisms composed of INTERACTIONS BW DNA AND SEVERAL DIFFERENT PROTEINS in research done and implemented in past years, it has been determined that the proteins bound to chromosomal DNA, the proteins that bind and are then bound to chromosomal DNA, are subject to changes occurring over the course of the lifetime of the eukaryotic cell whose dna they are bound to these changes, which cause changes in the composition of the proteins attached to the DNA, affect the degree of compaction of the chromatin CHROMOSOMES ARE VERY DYNAMIC STRUCTURES chromosomes are v dynamic structures, and these structures alternate bw TIGHT AND LOOSE COMPACTION that is why they are known as dynamic bc they alternate bw tight and loose compaction their level of compaction is never stagnant chromosomes are dynamic structures whose level of compaction changes according to the changes that occur in protein composition

eukaryotic chromosomes

EUKARYOTIC SPECIES HAVE ONE OR MORE SETS OF CHROMOSOMES each set of chromosomes that a eukaryotic species has is composed of SEVERAL DIFFERENT LINEAR CHROMOSOMES each set of chromosomes that a eukaryotic species has is composed of several different LINEAR CHROMOSOMES looking at humans specifically, humans HAVE 2 SETS OF 23 CHROMOSOMES EACH- this comes out to a total of 46 chromosomes humans have multiple sets of chromosomes, each of the sets is composed of a multitude of linear chromosomes humans have 2 sets of chromosomes, there are 23 chromosomes per set, making for a total of 46 chromosomes within a eukaryotic species THE TOTAL AMOUNT OF DNA within EUKARYOTIC SPECIES is usually much greater than the total amount of DNA within cells of bacterial species, than that found in bacterial cells therefore when looking at eukaryotic genomes, eukaryotic genomes CONTAIN MANY MORE GENES THAN DO THEIR BACTERIAL COUNTERPARTS bacterial genomes eukaryotic genomes contain far more genes than bacterial genomes, their counterparts what is a distinguishing distinct identifying feature of eukaryotic cells? within eukaryotic cells, their chromosomes are located within a specific entity within the cell they are located inside of the cellular compartment known as the nucleus THE CHROMOSOMES ARE LOCATED IN A SEPARATE INDIVIDUAL CELLULAR COMPARTMENT DESIGNATED AS THE NUCLEUS in order for eukaryotic dna to fit inside this specified, individual entity designated as the nucleus within a given eukaryotic cell, the EUKARYOTIC DNA must be compacted by a remarkable amount the length of the eukaryotic dna must be compacted dramatically in order for the entirety of the eukaryotic dna to fit inside of that particular cellular compartment, the nucleus similar to what occurs in bacterial chromosome compaction, there is a binding of the eukaryotic dna to many different cellular proteins in order to accomplish the appropriate amount of compaction required to fit all of that dna within the eukaryotic cell what is the DNA-protein complex that comes about due to the need for compaction designated as? this dna protein complex that comes about due to the need for compaction in order to fit within the eukaryotic nucleus, the binding of dna to a multitude of cellular proteins promoting compaction, is identified as CHROMATIN chromatin IS A DYNAMIC STRUCTURE chromatin is a dynamic structure that is able to change its SHAPE AND COMPOSITION DURING THE LIFE OF A CELL during the life of a cell, chromatin is able to change and alter its shape and composition different eukaryotic species VARY DRAMATICALLY IN THE SIZE OF THEIR GENOMES looking at eukaryotic species and moving from one species to another, you will see dramatic changes in the sizes of genomes as you move from one eukaryotic species to another the chart that is given to us is showing the size of the genomes of various eukaryotic species on a log scale this variation in genome size is usually not related to the complexity of species the complexity and complications and set up of a species is usually not related to the size of a species's genome an example showcasing the the size of a genome is not in any way related to how complex an organism is THERE ARE TWO CLOSELY RELATED SPECIES OF SALAMANDER these two closely related species of salamander are known as Plethedon Richmondi and plethodon larselli these two closely related species of salamander designated as plethedon Richmondi and plethodon larsellia are two closely related salamander species THAT DIFFER GREATLY IN GENOME SIZE these two closely related salamander species differ greatly in genome size THE GENOME of plethodon larselli is more than twice the size of the plethodon richmondi salamander species however, the genome of the plethodon larselli, despite being twice as large as the genome of the plethodon richmondi, probably does not contain more genes than the genome of the plethodon richmondi then why are the genome sizes of plethodon larselli and plethodon richmondi so different? why is the genome of the plethodon larselli more than twice as large as the genome of the plethodon richmondi? how do we explain this dramatic difference in genome size? the additional dna found in the genome of plethodon larselli is due to THE ACCUMULATION OF REPETITIVE DNA sequences the accumulation of repetitive DNA sequences in multiple copies due to the accumulation of repetitive DNA sequences found in multiple copies, there is a dramatic difference in the size of the genomes of plethodon larselli and plethodon richmondi where the size of the plethodon larselli genome is twice that of the size of the plethodon richmondi genome in some species, these repetitive DNA sequences found in a multitude of copies CAN ACCUMULATE TO ENORMOUS LEVELS, levels that cause dramatic differences in genome size amongst v closely related species, such as plethodon larselli and plethodon richmondi in particular species these repetitive DNA sequences found in a multitude of copies can accumulate to ENORMOUS LEVELS in particular species, these repetitive DNA sequences found in multiple copies can accumulate to enormous levels, levels that can cause enormous and dramatic changes in genome size amongst closely related species that should have v similar genome sizes these highly repetitive sequences of DNA, repetitive sequences that occur quite frequently throughout the genome, DO NOT ENCODE PROTEINS these highly repetitive sequences of DNA do not encode proteins the function of these highly repetitive DNA sequences remain investigated, as researchers have not been able to pinpoint their exact function, the function/purpose that they serve besides making the genome of an organism dramatically larger the function of these highly repetitive sequences is a subject of much interest as well as controversy over what purpose these highly repetitive sequences serve in the genomes of particular individuals, particular species

genomic imprinting and its biological significance

GENOMIC IMRPINTING- VERY NEW AND EXCITING genomic imprinting has been discovered in many mammalian genes (so amongst mammals, the phenomenon and implementation of genomic imprinting is more common and widespread than previously thought) in some cases, the maternally inherited alleles are transcriptionally active and produce a functional gene product in other cases, the paternally inherited alleles are transcriptionally active and produce a functional gene product in both cases, the other inherited allele is not transcriptionally active and does not produce a gene product what is the biological significance of imprinting? lots of speculation on its significance there are several hypothesis that have been proposed to explain the possible ways in which genomic imprinting may be beneficial there is one hypothesis by David Haig: this explains the benefits of genomic imprinting through the differences found in bw the female and male mammalian reproductive patterns so David Haig is looking at the ways in which female and male mammalian reproductive patterns can be distinguished, and how that intertwines with genomic imprinting (and possibly explains the benefits of genomic imprinting) Ch. 24 and previously learned concept- the phenomenon of natural selection, this phenomenon of certain traits being selected to proliferate and others being selected out of a population is a process that favors the types of genetic variation that result in a reproductive advantage (ie, the ability to reach the age of reproduction and pass on the same trait that allowed them to live long enough and successfully procreate to their offspring) there may be differences in regards to which advantageous traits are passed on to the offspring, depending on the sex of the offspring (the probability of passing on an advantageous trait changes when you look at the sex of the organism) within a multitude of mammalian species, females may mate with multiple males (multiple male partners) due to the female mating within multiple males, there can be embryos generated within her uterus that contain genetic material from different fathers individually (one embryo resulting from one coupling, another resulting from a different one, where the mother and the maternally inherited genes remain the same, but the father and the paternally inherited genes shift as you move from embryo to embryo) within males, if there are genes that inhibit embryonic growth, it would be advantageous for those genes to be silenced within their genetic material, so that embryonic growth can proceed therefore, within the multitude of embryo's in the mother's uterus, those embryos with the paternally inherited genes where genes coding for the inhibition of embryonic growth are silenced are more likely to proliferate, survive and develop into a mature and healthy organism that embryos within the mother's uterus with paternally inherited genes where the genes coding for the inhibition of embryonic growth are not silenced, and their growth is therefore inhabited therefore the embryos with the paternally inherited genes where the genes coding for the inhibition of embryonic growth are silenced will survive and mature and be born as developed fetuses, containing those genes they will pass on to their offspring that will result in proper embryonic development however in females, the rapid growth of embryos may serve as a disadvantage the rapid growth of embryos can cause the mother to be drained of her biological resources in trying to accommodate the rapid growth of the fetus therefore within females, and the maternally inherited genetic material, the genes coding for rapid embryonic growth would be silenced amongst females, the silencing of the genes coding for rapid embryonic growth would be advantageous because all of the offspring would not be competing for resources, and the mother herself would not be drained and she would pass on this advantageous trait to her female offspring, who would also not experience any drain due to rapid embryonic growth, as they will inherit the maternal genes with genes coding for rapid embryonic growth silenced the above hypothesis is consistent with research done on genomic imprinting within several mammalian genes one of these mammalian genes is Igf2, coding for enhancement of growth within females, this gene coding for growth enhancement is silenced (probably to ensure less competition amongst her developing embryos for nutrition, as well as less draining of her biological resources) within males, this gene coding for growth enhancement is not silenced, probably because it is advantageous for the offspring to undergo growth enhancement and thrive into well developed organisms however, there are several imprinted genes that have nothing to do with embryonic development, that researchers want to further investigate to fully understand the scope of genomic imprinting

genetic material

Genetic material is transmitted from parent to offspring Genetic material is transmitted from parent to offspring Genetic material is transmitted from parent to offspring Genetic material is transmitted from parent to offspring Genetic material is also transmitted from cell to cell For transmission to occur, in order for the transmission of genetic material from parent to offspring and from cell to cell to occur, in order for the transmission of genetic material from parent to offspring and from cell to cell to occur, the genetic material must be copied There is a process that involves the genetic material being copied in order for said genetic material to be properly transmitted from parent to offspring and from cell to cell, this process is recognized and designated as dna replication During the process of dna replication that involves the copying of genetic material, the original dna srands are used as templates for the synthesis of new dna strands The original dna strands are used as templates for the synthesis of new dna strands Important features of the double helix that are extraordinarily important to the process of replication Important features of the double helix that are extraordinarily important to the process of the replication of genetic material, the replication of NDA The double helix is composed of two DNA strands The double helix is composed of two DNA strands The double helix is composed of two DNA strands The individual building blocks of each strand are nucleotides The individual building blocks of each dna strand that composes the double helix are nucletodies The nucleotides contain one of the four bases: adenine, thymine, cytosine, or guanine The double stranded structure, the double helix, the double stranded structure composed of the two dna strands containing sequences of nucleotides, the nucleotides of DNA being adenine, thymine, guanine, and cytosine, the double stranded structure of dna, the double helix, the double stranded structure of dna is held together due to base stacking and due to hydrogen bonding bw complemetnary nitrogenous bases, bw the nitrogenous bases adenine and thymine and the nitrogenous bases guanine and cytosine There are two hydrogen bonds bw the nitrogenous bases adenine and thymine And there are three hydrogen bonds bw the nitrogenous bases guanine and cytosine The presence of guanine and cytosine within a dna double helix contributes to the stability of the double helix, the stability of the dna double helix structure The presence of guanine and cytosine within a dna double helix contributes to the stability of the double helix The presence of guanine and cytosine within a dna double helix contributes to the stability of the double helix, as the The presence of guanine and cytosine within a dna double helix contributes to the stability of the double helix, as there are three hydrogen bonds bw guanine and cytosine as opposed to the two hydrogen bonds bw adenine and thymine A critical feature of the double helix structure is that the adenine hydrogen bonds with thymine the nitrogenous base adenine on one strand binds with the nitrogenous base thymine n the other, and that guanine hydrogen bonds with cytosine, the nitrogenous base guanine on one strand hydrogen bonds (3 hydrogen bonds) with the nitrogenous base cytosine on the other This is recognized as Chargaff's rule, the AT/GC rule, and this rule established by Chargaff is the basis for the complementarity of the base sequences within double stranded dna The AT/GC rule by Chargaff is the basis for the complementarity of the base sequences within double stranded dna, the rule of AT/GC is responsible for the complementarity of the base sequences within double stranded dna Another feature worth noting is that the strands within a double helix, the strands within a double helix have an antiparallel arrangement The strands within a double helix have an antiparallel arrangemtns Another feature worth noting is that the strands within a double helix have an antiparallel arrangement, one strand is running in the 5 prime to 3 prime direction while the complementary strand is running in the 3 prime to 5 prime direction the directionality of a strand is determined by the orientation of sugar molecuels the directionality of a strand is determined by the orientation of sugar molecules the directionality of a strand is determined by the orientation of sugar molecules, the orientation of the sugar molecules of the pentose sugars within the sugar phosphate backbone of a dna strand determines the directionality of the strand, the orientation of the sugar molecules, the orientation of the pentose sugars the issue of directionality will prove important when we consider the functionality the function of the ezmyes that are responsible for the synthesis of new dna dna replication is reliant upon the complementarity of the DNA strands dna replication is reliant upon the complementarity of the DNA strands, the complementarity of the DNA strands according to the AT/GC rule of Chargaff during the replication process, during the process of dna replication during the process of dna replication, the two complementary strands of dna come apart, and they serve as TEMPLATE STRANDS OR PARENTAL STRANDS for the synthesis of two new strands of dna the two dna strands composing the double stranded double helix of dna come apart during dna replication, they separate from one another and serve as the TEMPLATE STRANDS OR THE PARENTAL STRANDS the two strands composing the double helix of dna during replication separate and are then designated and serve as the template strands, or the parental strands, for the synthesis of two new strands of dna to occur after the double helix of dna has separated, the individual nucleotides now have access to the template strands once the two dna strands composing the double helix of dna have separated, the individual nucleotides now have access to the template strands once the two dna strands composing the double helix of dna have separated from one another, the individual nucleotides now have access to the template strands hydrogen bonding bw individual nucleotides that now have access to the template strands due to the separation of the two strands forming the double helix of dna into nonintertwined strands, hydrogen bonding bw the nucleotides the individual nucleotides and the template/parental srands must obey the AT/GC rule in order to complete the replication process, a covalent bond is formed bw the phosphate of one nucleotide and the sugar molecule, the pentose sugar of another nucleotide in order for the replication process to be completed, a covalent bond is formed bw the phosphate of one nucleotide and the sugar molecule, the pentose sugar of another nucleotide the two newly synthesized strands, the two newly synthesized daughter strands are designated as daughter strands the two newly synthesized strands are designated as daughter strands the two newly synthesized strands are designated as daughter strands, formed by independent and individual nucleotides that were able to hydrogen bond to the template/parental strands, there are two newly synthesized strands known as daughter strands the base sequences are identical in both of the double stranded molecules after dna replication has occurred therefore dna is replication so that copies of dna contain the exact same genetic information, the same sequence as the original molecule

the consequences of gene redundancy in a genetic cross

George Shull conducted one of the first studies that showcased the phenomenon of gene redundancy he researched a weed known as shepherd's purse this weed is a member of the mustard family the trait he analyzed specifically was the shape of the seed capsule of the shepherd's purse plant the shape of the seed capsule is normally triangular there are particular strains of shepherd's purse that produce smaller ovate (circular) capsules, and these smaller ovate seed capsules are due to loss of function alleles and their homozygous recessive appearance in two different genes that contribute to the overall morphology of the seed capsule, tt and vv Shull crossed a true-breeding plant with triangular capsules (the wild type dominant phenotypic trait) with a plant with smaller ovate seed capsules the first filial generation all had triangular seed capsules however, there was a surprising result in the second filial generation he observed a 15:1 ratio of shepherd's purses with triangular capsules to shepherd's purses with smaller, ovate capsules this result can be explained by gene redundancy having one functional copy of either of the two genes (T or V) is enough to produce the triangular phenotype, to have the triangular shape of the seed capsules expressed by a functional gene T and V are functional alleles of redundant genes that similarly contribute to the phenotypic expression of the same trait only one of these genes is necessary for seed capsules of shepherds purses to have a triangular shape when the functionality of both genes is knocked out, then we have a phenotypic change with the ttvv homozygote, where the seed capsules are smaller and ovate

Hershey and Chase

Hershey and Chase were two scientists that provided evidence that DNA is the genetic material of the T2 phage Hershey and Chase were two scientists that provided evidence that DNA is indeed the genetic material of the T2 phage Hershey and Chase provided evidence that DNA is indeed the genetic material of the T2 phage Hershey and Chase provided evidence that DNA is indeed the genetic material of the T2 phage Hershey and Chase provided evidence that DNA is the genetic material of the T2 phage there was a second experimental approach implemented that indicated that DNA is the genetic material there was a second experimental approach implemented that indicated that DNA is indeed the genetic material, that DNA is indeed the transforming principle this second experimental approach came from studies conducted and implemented by Alfred Hershey and Martha Chase in 1952 the research that they conducted that Alfred Hershey and Martha Chase in 1952 conducted centered and concentrated on the study of a virus known as T2 the studies and experiments that these aforementioned scientists Hershey and chase implemented were experiments that focused on a particular virus designated as T2 their experiments focused on a particular virus designated as T2 their experiments focused on a particular virus designated as T2 this particular virus known and designated as T2 infects escehrichia coli bacterial cells this particular virus designated as T2 infects escherichia coli bacterial cells, and due to this particular virus T2 infecting escherichia coli bacterial cells, this particular virus designated as T2 is known as a bacteriophage, or simply a phase the research conducted by these two scientists Hershey and Chase concentrated on a specific virus known and designated as T2, and this particular virus infects escherichia coli bacterial cells this particular virus that they focused their implemented studies on infects escherichia coli bacterial cells specifically this particular virus that they focused their implemented studies on infects escherichia coli bacterial cells specifically this particular virus that the focused their implemented studies on, the virus designated as T2 that Hershey and Chase focused their implemented studies on infects particularly, specifically escherechia coli bacterial cells, and therefore this T2 virus is recognized as a bacteriophage or simply a phage this T2 virus is recognized as a bacteriophage or simply a phage due to it specifically infecting escherechia coli cells the external structure of the T2 phage is known as the capsid or phage coat the external structure of the T2 phage is known as the capsid or phage coat the external structure of the T2 phage is known as the capsid or phage coat the external structure of the T2 phage is known as the capsid or the phage coat the external structure of the T2 phage is known as the capsid or the phage coat the external structure of the T2 phage is known as the capsid or the phage coat the external structure of the T2 phage is known as the capsid or the phage coat the external structure of the T2 phage is known as the capsid or the phage coat the capsid or the phage coat that constitutes the external structure of the T2 phage is composed of: a head sheath tail fibers base plate the components of the capsid or the phage coat are a head, sheath, tail fibers, and a base plate the components of the capsid or the phage coat are a head, sheath, tail fibers, and a base plate the components of the capsid or the phage coat are a head, sheath, tail fibers, and a base plate the components of the capsid or the phage coat are a head, sheath, tail fibers, and a base plate the components of the capsid or the phage coat are a head, sheath, tail fibers, and a base plate the components of the capsid or the phage coat are a head, sheath, tail fibers, and a base plate the components of the capsid or the phage coat are a head, tail, sheath fibers, and base plate biochemically, the capsid or the phage coat is composed entirely of protein biochemically, the capsid or the phage coat is composed entirely of protein biochemically the capsid or the phage coat is composed entirely of protein biochemically the capsid or the phage coat is composed entirely of protein biochemically the capsid or the phage coat is composed entirely of protein the protein that composes the capsid or the phage coat includes several different polypeptides the protein that composes the capsid or the phage coat includes several different polypeptides the protein that composes the capsid or the phage coat includes several different polypeptides the protein that composes the capsid or the phage coat includes several different polypeptides the protein that composes the capsid or the phage coat includes several different polypeptides DNA is found inside of the head of the capsid or phage coat DNA is found within the head of the capsid or the phage coat DNA is found within the head of the capsid or the head of the phage coat the head of the capsid/phage coat from a molecular point of view, this virus is rather simple from a molecular point of view this virus is rather simple from a molecular point of view this virus is rather simple from a molecular point of view this virus is rather simple from a molecular point of view this virus, the T2 virus is rather simple and this virus, the T2 virus is composed of only two types of macromolecules: DNA found within the head of the capsid/phage coat, and proteins this virus, the T2 virus is composed of only two types of macromolecules the T2 virus is composed of only 2 types of macromolecules, DNA found within the head of the capsid/phage coat, ad proteins although the viral genetic material contains the blueprint to make new viruses, a virus itself CANNOT SYNTHESIZE NEW VIRUSES the viral genetic material does indeed contain the blueprint to make new viruses however a virus on its own is not able to produce and synthesize new viruses a virus on its own is not able to produce and synthesize new viruses a virus on its own is not able to produce and synthesize new viruses a virus's genetic material does contain the blueprint in order to synthesize new viruses a viruses's genetic material does contain the blueprint in order to synthesize viruses, however a virus is not able to, on its own, synthesize new viruses a virus on its own is not able to synthesize new viruses a virus on its own is not able to synthesize new viruses a virus on its own is not able to synthesize new viruses a virus on its own is not able to synthesize new viruses instead, a virus must introduce its genetic material into the cytoplasm of a living cell a virus must introduce its genetic material into the cytoplasm of a living cell a virus must introduce its genetic material into the cytoplasm of a living cell a virus must introduce its genetic material into the cytoplasm of a living cell a virus must introduce its genetic material into the cytoplasm of a living cell a virus must introduce its genetic material into the cytoplasm of a living cell in order to proliferate, in order to synthesize new viruses, it is not capable of synthesizing new viruses on its own despite its genetic material containing a blueprint that can produce new viruses, a virus is still not capable of synthesizing new viruses on its own in the case of T2, in the case of a T2 virus, this first involves the attachment of its tail fibers ot the bacterial cell wall in the case of the T2 virus and the insertion of its genetic material into the cytoplasm of a living cell, the process first involves the attachment of its tail fibers to the living bacterial cell wall first there is the attachment of the tail fibers to the bacterial cell wall then there is the subsequent injection following the attachment of the tail fibers to the bacterial cell wall, the subsequent injection of the genetic material of the T2 virus into the cytoplasm of the cell the phage coat remains attached on the outside of the bacterium, the phage coat remains attached on the outside of the bacterium and does not enter the cell the tail fibers of the T2 virus attach to the living bacterial cell wall, and subsequently the genetic material of the T2 virus is inserted into the cytoplasm of the living bacterial cell the phage coat remains on the outside of hits bacterial cell, it remains attached to the outside of the bacterium and does not enter the cell after the entry of the viral genetic material, the bacterial cytoplasm provides all of the machinery required to make viral proteins and DNA after the injection of the viral genetic material into the cytoplasm of the living bacterial cell, the cytoplasm of this living bacterial cell contains all of the machinery necessary, and provides all of the machinery necessary to make viral proteins and DNA then, all the viral proteins and DNA that are produced by the machinery provided by the bacterial cell all of the machinery required to make viral proteins and DNA is provided by the cytoplasm of the bacterial cell that the viral dna is injected into once all of the viral proteins and DNA are produced, the viral proteins and the DNA produced by the machinery provided by the bacterial cytoplasm conglomerate amongst one another, gather, and assemble to make new viruses that are then released from that bacterial cell by lysis lysis is cell breakage in order to verify that DNA is the genetic material of T2, Hershey and Chase devised and conceited a method to separate the phage coat, which remains attached to the outside of the bacterium, the outside of the bacterial cell will the tail fibers of T2 attach to the bacterial cell wall and the viral genetic material is injected into the cytoplasm of the bacterial cell Hershey and chase in order to verify that DNA is indeed the genetic material of the T2 virus, devised and concocted a method to separate the phage coat which remains attached to the outside of the bacterium from the genetic material that is subsequently injected into the cytoplasm they were aware of previously implemented microscopy experiments implemented by Thomas Anderson these previously implemented microscopy experiments showcased that the T2 phage attaches itself to the outside of the bacterium through the utilization of its tail fibers attaching to the bacterial cell wall Hershey and Chase reasoned that this is a fairly precarious and most likely fairly unstable attachment, the attachment of the phage to the outside of the bacterium, facilitated by the attachment of the tail fibers of the T2 virus to the bacterial cell wall they reasoned that this attachment facilitated by the tail fibers of the T2 virus attaching to the bacterial cell wall was precarious and could be disrupted and broken by subjecting the bacteria to high shear forces they reasoned that they could potentially disrupt this attachment of the phage to the outside of the bacterium facilitated by the attachment of the tail fibers of the T2 virus to the bacterial cell wall by subjecting the bacterium to high shear forces the high shear forces they would subject the bacterium to in order to disrupt the attachment of the phage to the outside of the bacterium, an attachment facilitated by the attachment of the tail fibers of the T2 virus to the bacterial cell wall the method that Hershey and Chase implemented was one where they exposed the bacteria to the T2 phage they exposed the bacteria to the T2 phage, allowing a sufficient amount of time for the viruses to attach themselves to the bacteria and then inject their genetic material into the cytoplasm of the bacteria they then sheared the phage coats from the surface of the bacteria, from their attachment to the outside of the bacteria (facilitated by the attachment of their tail fibers to the bacterial cell wall) through the utilization of a blender treatment in this way, the phage's genetic material, the genetic material of the phage, with had been injected into the cytoplasm of the bacterial cells, could be separated from the phage coats that were sheared away the genetic material of the phage, which had been injected into the cytoplasm of the bacterial cells, could be separated from the phage coats that were sheared away from the outside of the bacterial cells Hershey and Chase utilized radioisotopes to distinguish proteins from DNA Hershey and Chase utilized radioisotopes to distinguish proteins from DNA Hershey and Chase utilized radioisotopes to distinguish proteins from DNA Hershey and Chase utilized radioisotopes to distinguish proteins from DNA Hershey and Chase utilized radioisotopes in order to distinguish proteins from DNA Hershey and Chase utilized radioisotopes in order to distinguish proteins from DNA sulfur atoms are found in proteins but they are not found in DNA sulfur atoms are found in proteins but they are not found in DNA sulfur atoms are found in proteins but they are not found in DNA sulfur atoms are found in proteins but they are not found in DNA sulfur atoms are found in proteins but they are not found in DNA phosphorus atoms are found in DNA but not in phage proteins phosphorus atoms are found in DNA but not in phage proteins phosphorus atoms are found in DNA but not in phage proteins phosphorus atoms are found in DNA but not in phage proteins 35 S is a radioisotope of sulfur 32 P is a radioisotope of phosphorus these two radioisotopes, 35 S and 32 P were utilized in order to specifically label phage proteins and DNA respectively these two radioisotopes, 32S a radioisotope of sulfur and 32P a radioisotope of phosphorus were utilized in order to label phage proteins and DNA respectively the 32S radioisotope of sulfur was utilized in order to label the phage proteins, as sulfur is found in proteins but is not found in DNA, so it could be utilized as a definitive marker for phage proteins the 32P radioisotope of phosphorus was utilized in order to label the DNA, as phosphorus is found within DNA but is not found within proteins, so this phosphorus radioisotope designated as 32P could be utilized to definitively label and distinguish DNA the researchers grew escherichia coli cells in media that contained either 35S or 32P The researchers grew Escherichia coli cells in media that contained 35S or 32P The researchers grew Escherichia coli cells in media that contained 35S or 32P The researchers grew Escherichia coli cells in media that contained 35S or 32P The researchers grew Escherichia coli cells in media that contained 35S or 32P The researchers grew Escherichia coli cells in media that contained 35S or 32P The researchers grew Escherichia coli cells in media that contained 35S or 32P The researchers grew Escherichia coli cells in media that contained 35S or 32P They then infected these Escherichia coli cells that were grown in media that contained 35s or 32P They then infected these Escherichia coli cells that were grown in media that contained 35S or 32P They then infected these Escherichia coli cells that were grown in media that contained 35S or 32P They then infected these Escherichia coli cells that were grown in media that contained 35S or 32P (recall that sulfur is found within proteins but not DNA, and phosphorus is found in DNA but not in phage proteins, therefor 35S labels and distinguishes proteins and 32P labels and distinguishes DNA) with T2 phages They then infected these Escherichia coli cells that were grown in media containing either 35S or 32P with T2 phages When these new phages were produced they were labeled with 35S or 32P In the experiment described, they began with Escherichia coli cells and two preparations of T2 phage that were obtained in this particular aforementioned manner Where escherichia coli was grown in media that contained either 35S or 32P, and then were infected with T2 phages, the new phages that were produced due to the infection of these Escherichia coli cells with T2 phages were labeled 35S or 32P There were Escherichia coli cells and two preparations of T2 phages that were obtained in this particular aforementioned manner One preparation was labeled with 35S in order to lable the phage proteins The other preparation of T2 phages was labeled with 32P in order to label the phage DNA So the phage proteins were labeled and distinguished with 35S, and the phage DNA was distinguished and labeled with 32P In separate flasks, each type of phage, the type labeled with 35S and the type labled with 32P was mixed with a new sample of E. Coli cells The phages were then given significant time to inject their genetic material into the Escherichia coli cells they were mixed with in those separate and individual flasks Then the sample the mixed sample, after the T2 phages labeled separately, one type of phage labeled with 35S mixing with Escherichia coli and then the other type of phage in a separate flask labeled with 32P mixed with Escherichia coli as well, the mixed sample, after the phages were given enough time to inject their genetic material into the Escherichia coli cells, the sample was subjected to shearing force using a blender, that would be able to separate the phage coats, the heads attached to the outside of the Escherichia coli cells due to the attachment of the tail fibers of the T2 phages to the bacterial cell walls, from the Escherichia coli cells The shearing force exerted on these mixed samples would separate the T2 phage heads, the phage coats of these T2 phages from the outside of the Escherichia coli bacterial cells, severing the attachment bw the two facilitated by the attachment of the tail fibers of the T2 phages to the bacterial cell walls of the Escherichia coli cells The treatment of the blender, the shearing force exerted upon the mixed sample was expected to remove the phage coat from the surface of the bacterial cell The sample was then subjected to centrifugation at a speed that would cause the heavier bacterial cells, the heavier and more weighted Escherichia coli cells to form a pellet at the bottom of the tube The light phage coats due to the centrifugation and the movement of the heavier and more weighted Escherichia coli cells to the bottom of the tube in the process of forming a pellet, the light phage coats due to this event would remain within the supernatant, would remain within the liquid above the pellet the light phage coats separated from the bacterial cell walls would remain in the supernatant, the liquid above the pellet the light phage coat separated from the bacterial cell walls would remain in the supernatant, remain in the liquid above the pellet when the sample was centrifugated the amount of radioactivity within the supernatant containing the phage coats that had been separated from the bacterial cells by shearing forces was determined using a Geiger counter the amount of radioactivity within the supernatant containing the phage coats that had been separated from the bacterial cells by shearing forces was determined using a Geiger counter the amount of radioactivity within the supernatant, emitted from either 35S or 32P within the supernatant was determined using a Geiger counter as seen in the data, most of the 35S isotope was found in the supernatant most of the 35 isotope, utilized to in order to label the phage proteins, as the phage proteins contain sulfur, most of the 35S isotope was found within the supernatant most of the 35S isotope was found within the supernatant because the shearing force exerted on the sample was expected to remove the phage coat from the Escherichia coli cells that had been infected by the T2 phages, this result indicates that empty phages contain primarily protein, they contain primarily the shearing force exerted on the sample separated the phage coats from the Escherichia coli cells that the T2 phages infected, and centrifugation resulting in this empty phage coats conglomerating within the supernatant of the tube, the liquid above the pellet containing the heavier and weighted bacterial cells that conglomerated at the bottom of the tube in a pellet after the shearing force separated them from the phage coats they were attached to the presence of 35S, the majority of the radioactive isotope 35S utilized in order to label phage proteins being found within the supernatant, the fluid above the pellet that contained all of the light phage coats, the majority of the radioactive isotope 35S being found within the supernatant on top of the pellet, the supernatant containing the empty phage coats, indicated that empty phages contain proteins, primarily proteins at that, considering the large and majority amount of 35 S being found within the supernatant containing the empty phages, and the comparably small amount of 32P labeling DNA being found within the supernatant containing the empty phages the indication was that within empty phages, they are composed of primarily protein by comparison, only about 35 percent of the 32P radioactive isotope utilized in order to label DNA was found within the supernatant containing the empty phages following shearing and centrifugation therefore the majorty of DNA was located within the bacterial cells, the Escherichia coli cells that had been infected by the T2 phages the majority of DNA was located within the bacterial cells that had conglomerated during centrifugation due to their weight in order to form a pellet therefore, most of the DNA was located within the bacterial cells in the pellet most of the DNA was located within the bacterial cells that had conglomerated during centrifugation and formed the pellet most of the DNA was located within the bacterial cells that had conglomerated during centrifugation and formed the pellet most of the DNA was located within the bacterial cells that had conglomerated during centrifugation and formed the pellet these results are consistent with the notion that the DNA is injected into the bacterial cytoplasm during infection these results are consistent with the notion that DNA is injected into the bacterial cytoplasm during infection these results are consistent with the notion that DNA is injected into the bacterial cytoplasm during infection implemented by the virus, which would be the expected result if DNA is indeed the genetic material by themselves, the evidence that was found within the experiment conducted was not enough to verifiably conclude that DNA is indeed the genetic material for example, you may have noticed that less than 100 percent of the phage protein was found within the supernatant containing the empty phages, not all of the phage protein was found solely within the empty phages within the supernatant liquid therefore some of the phage protein could have been introduced into the bacterial cells, considering that not all of the phage protein was found within the empty phages of the supernatant some of the phage protein could have potentially been introduced into the bacterial cells and therefore could potentially function as the genetic material instead of DNA nevertheless, the results of Hershey and Chase and their experimentation was consistent with the conclusion that the genetic material responsible for the transformation of bacterial cells initated and implemented by viruses is DNA and not protein overall the studies of the T2 phage were extremely influential in convincing the scientific world that DNA is indeed the genetic material, and that protein is not DNA is the genetic material ACED ALL YOUR FINALS!

reciprocal translocations

INDIVIDUALS WITH RECIPROCAL TRANSLOCATIONS MAY PRODUCE ABNORMAL GAMETES DUE TO THE SEGREGATION OF CHROMOSOMES individuals who contain reciprocal translocations may produce abnormal gametes due to the segregation of chromosomes individuals who contain reciprocal translocations may produce abnormal gametes due to the segregation of these chromosomes individuals who carry balanced translocations have a greater risk of producing gametes with unbalanced combinations of chromosomes individual who carry balanced chromosomes may not be phenotypically impacted themselves, due to the balanced translocation not resulting in an alteration of the totality of genetic material contained within these individuals due to the totality of genetic material remaining the same and unaltered despite the chromosomal aberration of a translocation occurring, individuals with these BALANCED TRANSLOCATIONS particularly one must focus on the balanced description of these translocations, these translocations are balanced, and therefore the genetic material the totality of genetic material contained within the individual is not altered, there is merely a rearrangement and slight shuffling of the genetic material instead however, despite the individual with the balanced translocation not experiencing any phenotypic effects or consequences due to the totality of genetic material not changing within their cells, merely a rearrangement of genetic material occurring, they have a greater risk of producing gametes WITH UNBALANCED COMBINATIONS OF CHROMOSOMES these individuals with balanced translocations that do not affect them phenotypically have a higher chance of forming gamete with unbalanced numbers of chromosomes, which will result in either phenotypically affected or nonviable zygotes when these gametes are fused with other gametes, even a genetically normal gamete whether or not this occurs, where or not an individual with a balanced translocation produces gametes with unbalanced numbers of chromosomes is dependent on the SEGREGATION PATTERN OF MEIOSIS I the segregation pattern of meiosis I influences whether or not an individual with a balanced translocation produces gametes with an unbalanced number of chromosomes the segregation pattern of meiosis I influences whether or not an individual with a balanced translocation produces gametes with an unbalanced number of chromosomes or not the segregation pattern of meiosis I influences whether or not an individual with a balanced translocation or balanced translocations produces gametes with an uneven and unbalanced number of chromosomes the segregation pattern of meiosis I, the segregation pattern of homologous pairs of chromosomes (sister chromatids that are attached to each other at centromeres but will be considered individual chromosomes once they segregate in meiosis II) in meiosis I influences whether or not an individual with a balanced translocation or balanced translocations forms gametes with unbalanced numbers of chromosomes in the example given, the parent carries a reciprocal translocation, where the overall amount of genetic material is not impacted by this chromosomal aberration of a reciprocal translocation, and this individual is expected to be phenotypically normal during meiosis, the homologous chromosomes attempt to synapse with one another THE HOMOLOGOUS CHROMOSOMES TEND TO SYNAPSE WITH ONE ANOTHER during meiosis, the homologous chromosomes tend to synapse with one another, synapse with one another and then experience genetic recombination and crossover because of the translocations in the individual's somatic cell that is going to be forming gametes, the PAIRING OF HOMOLOGOUS REGIONS LEADS TO AN UNUSUAL STRUCTURE FOR A SYNAPSE there is the formation of an unusual structure due to the pairing of homologous regions of chromosomes there is the formation of an unusual structure due to the pairing of homologous regions of chromosomes that occurs under the influence of the translocations in the somatic cell of the individual that will undergo meiosis in order to form gametes because of the translocations, the pairing of homologous regions leads to the formation of an unusual structure THIS UNUSUAL STRUCTURE CONTAINS FOUR PAIRS OF SISTER CHROMATIDS making for a total of 8 sister chromatids, 4 pairs of sister chromatids forming a structure for genetic recombination and crossing over, due to the translocations within the chromosome this is designated as a TRANSLOCATION CROSS the structure of 4 pairs of sister chromatids, a total of 8 chromatids, that conglomerate in order to create a structure for synapsing during meiosis, and this occurs because of the translocations present amongst these pairs of sister chromatids TO UNDERSTAND THE SEGREGATION OF TRANSLOCATED CHROMOSOMES pay close attention to the centromeres to understand the segregation of translocated chromosomes, play close attention to the centromeres for these translocated chromosomes that are part of a structure of 4 pairs of sister chromosomes, 2 pairs containing the chromosomal aberration of a reciprocal translocations, the way that they are eventually segregated depends upon the centromeres the expected segregation pattern of these chromosomes forming this structure is governed by the centromeres each haploid gamete should receive ONE CENTROMERE LOCATED ON CHROMOSOME 1 AND ONE CENTROMERE THAT IS LOCATED ON CHROMOSOME 2 that is why the segregation of these chromosomes is dependent upon their centromeres one possibility for this to occur, in which each haploid gamete that is formed contains one centromere from chromosome 1 and one centromere from chromosome 2 is alternate segregation when does alternation segregation occur? how does alternate segregation occur? alternate segregation occurs when the chromosomes that are DIAGONAL TO EACHOTHER WITHIN THE TRANSLOCATION CROSS within the structure of 4 pairs of sister chromatids, the chromosomes that are diagonal to one another in this structure will sort into the same cell one daughter cell will receive two normal chromosomes,, and the other cell will receive the two chromosomes that underwent a reciprocal translocation in alternate segregation, one cell created from meiosis one will contain the pairs of sister chromatids that underwent a reciprocal translocation, it will take those two abnormal chromosomes with chromosomal aberrations the chromosomes that are located diagonally across from one another will be sorted into the same cell, the chromosomes that underwent reciprocal translocations are located diagonally across from one another and therefore will be sorted into the same cell, and the normal chromosomes are also located diagonally across from one another in the translocation cross, the 4 pairs of sister chromatids forming a structure, a synapse there one cell will end up with both pairs of sister chromatids that underwent reciprocal translocation and one cell will end up with both normal pairs of sister chromatids this will result in the expected production after meiosis ii of four haploid cells two of the haploid cells will contain normal chromosomes, and two of the haploid cells will contain the chromosomes that underwent reciprocal translocation, but they will contain chromosomes that underwent a balanced translocation, the maintenance of the total amount of genetic material will occur

intergenic region

INTERGENIC REGIONS ARE NONTRANSCRIBED REGIONS OF DNA these intergenic regions are nontranscribed regions of dna these nontranscribed regions of DNA are located BW ADJACENT GENES nontranscribed regions of DNA are located between adjacent genes intergenic sequences are sequences of DNA that are located bw adjacent genes, and they are not transcribed intergenic sequences, recall that intergenic sequences are sequences of DNA that are located bw adjacent genes, and these sequences of DNA that are located bw adjacent genes are not transcribed

meiotic nondisjunction can produce aneuploidy or polyploidy

MEIOTIC NONDISJUNCTION CAN PRODUCE ANEUPLOIDY OR POLYPLOIDY meiotic nondisjunction can produce aneuploidy or polyploidy meiotic nondisjunction can produce aneuploidy or polyploidy nondisjunction during meiosis, meiotic nondisjunction can occur during meiosis I or meiosis II if meiotic nondisjunction occurs during meiosis I, an entire bivalent, two pairs of sister chromatids that have formed a bivalent migrates to one pole following the completion of meiosis, the four resulting haploid cells, the four resulting haploid gametes produced from this event, from meiotic nondisjunction in meiosis I are all abnormal if meiotic nondisjunction occurs during anaphase II of meiosis II, the net result is two abnormal and two normal haploid cells out of the four haploid cells, the four haploid gametes produced, there are two abnormal haploid cells and two normal haploid gametes due to the meiotic nondisjunction occurring during meiosis II if there is a gamete that is missing a chromosome and is still viable and participates in the process of fertilization, the resulting offspring is monosomic for the missing chromosomes, the chromosome that was missing from that gamete resulting from meiotic nondisjunction ALTERNATIVELY if there is a gamete carrying an extra chromosome, and this gamete carrying an extra chromosome unties with a normal gamete, the offspring resulting from the combination of this abnormal gamete with a normal gamete with a normal and expected amount of genetic material will result in a trisomic offspring, containing extra copies of those particular chromosomes that one of the gametes contributing to its formation had IN RARE CASES ALL OF THE CHROMOSOMES WITHIN A CELL CAN UNDERGO NONDISJUNCTION and migrate to one of the daughter cells in rare cases all of the chromosomes within a cell can undergo nondisjunction and migrate to one of the daughter cells in rare cases all of the chromosomes within a cell can undergo nondisjunction and migrate to one of the daughter cells, all of the chromosomes within a cell can undergo nondisjunction and migrate to one of the daughter cells the net result of this process where all of the chromosomes within a cell migrate to one of the daughter cells is designated as complete nondisjunction the cell that does not receive any of the chromosomes is a nonviable gamete, a nonviable cell that will not be able to participate in fertilization however, the diploid cell created due to all of the chromosomes undergoing nondisjunction and migrating to a single daughter cell, this diploid cell may participate in fertilization with a normal haploid gamete in order to produce a triploid individual this diploid cell may participate in fertilization with a normal haploid gamete in order to produce a triploid individual, and this combination of this diploid cell resulting from complete nondisjunction, all of the chromosomes within this cell migrating to one daughter cell rather than splitting bw two daughter cells, combining with a normal gamete with a normal amount of genetic material will result in a triploid individual, an offspring w 3 sets of chromosomes therefore, complete nondisjunction can produce individuals that are polyploid complete nondisjunction can produce individuals that are polyploid, individuals with multiple sets of chromosomes, more than the requisite number of sets of chromosomes that is required

a second important reason for cell division

MULTICELLULARITY IS ANOTHER IMPORTANT REASON FOR CELL DIVISION TO OCCUR cell division occurs in order for asexual reproduction to occur however, another reason that the process of cell division occurs is due to the multicellularity of organisms there are species such as: PLANTS ANIMALS THE MAJORITY OF FUNGI SOME PROTISTS these species are all derived from a single cell (a single embryonic cell in some cases) that has undergone repeated mitotic divisions, repeated cellular divisions in order to develop into a complete organism humans begin as a fertilized egg a zygote formed due to the fusion of a sperm cell and egg cell this zygote, this fertilized egg starts off as a single cell and then undergoes repeated mitotic division in order for this single fertilized egg, this zygote, this cell to develop into an entire human individual, a complete and developed human individual with TRILLIONS OF CELLS a human individual starts out as a single fertilized egg, a single zygote, a cell that is the combination of an egg cell and a sperm cell, and undergoes repeats of mitotic division, repetitive cellular division, until a complete and developed organism consisting of trillions of cells is created the precise transmission of chromosomes containing the entirety of that individual's genes during the occurrence of every single cellular division that occurs in order to create the fully developed human with trillions of cells is crucial, the precise transmission of chromosomes containing all of the genetic material of that individual is critical within cellular division and the subsequent development of organelles it is extremely important that all cells of an organism resulting from proliferation receive the correct amount of genetic material during cellular division all the cells of the body that proliferate from an original cell must receive the appropriate and correct amount of genetic material, and the reception of the appropriate amount of genetic material needs to be ensured throughout the process of mitosis/cellular division, as diploid cells proliferate from an original diploid cell THE PROCESS OF CELL DIVISION/MITOSIS REQUIRES 3 THINGS: the three things the process of cell division/mitosis requires is: DUPLICATION ORGANIZATION DISTRIBUTION of chromosomes the three things the process of cell division/mitosis requires is DUPLICATION of the chromosomes (during the synthesis phase that occurs prior to mitosis, duplication of all the genetic material), ORGANIZATION of the chromosome (the genetic material, particularly all of the genetic material including that that has been replicated being distinguishable and distinct from one another), and DISTRIBUTION of the chromosomes, (the appropriate number of chromosomes being received by each of the 2 daughter cells that proliferate from the original diploid cell) the process of division in bacteria bacteria contain a single circular chromosome- a single circular chromosome is all of their genetic material A SINGLE CIRCULAR CHROMOSOME IS ALL OF THEIR GENETIC MATERIAL all of a bacterium's genetic material is a single circular chromosome the division process is relatively simple for bacteria for bacteria to proliferate into more bacteria, the division process is simple and straightforward prior to the process of cellular division occurring in bacteria, the bacteria DUPLICATE THEIR SINGLE CIRCULAR CHROMOSOME the single circular chromosome of the bacteria is duplicated then the two copies of the single circular chromosome of the bacteria are distributed evenly, one copy of the single circular chromosome being distributed to each daughter cell each daughter cell receives one copy of the single circular chromosome (recall that one copy of the single circular chromosome from the original was created) THIS PROCESS IS KNOWN AS BINARY FISSION eukaryotes in contrast, HAVE MULTIPLE NUMBERS OF CHROMOSOMES THESE MULTIPLE NUMBERS OF CHROMOSOMES OCCUR AS SETS these multiple numbers of chromosomes are sorted into sets this added complexity of the multiple numbers of chromosomes occurring as sets within eukaryotes makes the process of cellular division amongst eukaryotes quite different there is a more complicated sorting process of the chromosomes that occurs during cellular division/mitosis in order to ensure that all of the daughter cells proliferating from the original mother cell receive the appropriate and proper amount of genetic information, genetic material with the added complexity, the process of cellular division still needs to ensure that each daughter cell receives the correct type and appropriate number of these correct types of chromosomes from the mother cell (that has during S phase gone under the process of replication, DNA replication) there is a mechanism designated as mitosis that is responsible for the organization and distribution (the sorting and distribution) of chromosomes during the process of cellular division, ensuring that each daughter cell receives the correct type and appropriate number of the correct types of chromosomes from the mother cell that they are proliferating from

Mary Lyon experiments and research done on dosage compensation

Mary Lyon in 1961 proposed the notion that dosage compensation that occurs within mammals (the phenomenon that causes the phenotypic expression within organisms possessing different levels of gene expression for the phenotype we are observing to be the same) occurs due to the inactivation of a single X chromosome within females (one of the female's X chromosomes turning into a Barr body and therefore becoming inactivated) Liane Russell also proposed this notion two lines of study were brought together due to these proposed notions made by Mary Lyon and Liane Russell the first evidence verifying this notion was one that arrived from cytological studies Murray Barr and Ewart Bertram identified a very condensed and compacted structure within the nuclei of somatic cells the nuclei where this very condensed and compacted structure was found were interphase nuclei these highly condensed and compacted structures found within the interphase nuclei of somatic cells were found only in the somatic cells of female cats, and not the somatic cells of male cats they designated this condensed and compacted structure they found in the interphase nuclei of the somatic cells of female cats, the Barr body Susumu Ohio correctly proposed the notion in 1960 that the condensed and compacted structure found in the interphase nuclei of the somatic cells of female cats and designated as the Barr body is a highly condensed X chromosome, and she was correct in addition to this cytological evidence found in 1949 by Murray Barr and Ewart Bertram, there was evidence known my Mary Lyon the examples she was familiar with were mammalian examples, amongst mammals with varying coat patterns different mammals would have differently colored coats, and could have patterns of colors on their coats an example of this is the calico cat the calico cat is a female cat that is heterozygous for a particular X-linked gene that wields a lot of influence over the color of the cat's coat this X-linked gene has an allele coding for orange, and an allele coding for black with calico cats, the orange and black patches of their coats are distributed differently varying from cat to cat the coat patterns vary as well, the locations of orange and black patches change and there is not a lot of consistency besides the relative unevenness of the patches of orange and black on their coats the calico pattern of orange and black patches is not found in male cats mosaic patterns similar to the calico pattern are found in the female mouse the hypothesis Lyon had for why the Barr body exists, why these patterns of calico orange and black occur in female calico cats, why the mosaic patterns occur in female mice was the following: X-inactivation in the cells of female mammals is what causes the presence of these highly compacted and condensed Barr bodies being found in the cells of female mammals, as well as the calico pattern of orange and black patches being found exclusively in female cats

Mendel experimentation with a single character

Mendel did not have an established hypothesis that could properly explain the formation of hybrids However, he did understand that if he conducted quantitative experiments, he might be able to uncover mathematical relationships amongst reproduction, governing mathematical principles that might explain reproduction, particularly the formation of hybrids empirical approach- he wanted to determine the relationships governing and determining and manipulating hereditary traits, how those traits are passed on empirical laws are the laws established by the usage of an empirical approach Mendel started with true-breeding plants that differed in regards to a single character (so they each had a variant of this character) this generation of true breeding plants that would be crossed with one another- designated as the parental generation/ P generation the crossing of these two true-breeding members of the parental generation is known as a P cross the offspring of the parental generation is known as the F1/first filial generation all plants of the F1 generation showed the phenotype of one parent, but not the other (showed the dominant trait, influenced by the dominant allele inherited from one parent that trumped the recessive allele inherited from the other) the F1 generation self fertilized, and this produced the F2/ second filial generation (where the morphology of the offspring was different and split due to two heterozygous allelic combinations breeding) the traits of the offspring were never intermediate in character, which disproved the blending mechanism of heredity theory that had been established the offspring always showcased a trait they shared with one of the parents, never both when the parents had variants of the same character (there was never an intermediate characteristic) he gleaned from his experimentation that one variant of a character is dominant over the other variant of a character an example of this- the green pod variant is dominant over the yellow pod variant, which is recessive recessive- means this variant is masked by the presence of a dominant trait (the presence of a dominant allele in the individual's allelic combination), but can reappear in subsequent generations if there is an allelic combination with 2 recessive alleles that occurs examples of recessive variants- yellow pods, dwarf stems when a true breeding plant with a dominant trait is crossed with a true breeding plant with a recessive trait, Mendel found that in the first filial generation, all of the offspring expressed the dominant trait however, in the subsequent generation resulting from the first filial generation self fertilizing, there were some offspring showcasing the dominant trait, and others showing the recessive trait (a smaller number) the proposal he gleaned from this was that the genetic determinants of traits (the factors that genetically determine what the trait of the offspring will be) are passed as "unit factors" interacting with one another from generation to generation he found a recurring pattern in regards to the second filial generation there was always a 3:1 ratio bw the dominant trait and the recessive trait he understood that genes segregate from one another when gametes are formed (that is how a gamete ends up with an allele, half of an allelic combination that is formed when it fuses with another gamete)

Mendel's experiments and loss-of-function alleles

Mendel encountered many loss-of-function alleles during his experimentation, found many defective genes lots of the recessive traits that he found expressed by some of his pea plants were expressed bc of genes being defective and losing their functionality

Morgan provided evidence for the linkage of x linked genes

Morgan provided evidence for the linkage of x linked genes Morgan provided evidence for the linkage of x linked genes Morgan provided evidence for the linkage of x linked genes Morgan provided evidence for the linkage of x linked genes Morgan provided evidence for the linkage of x linked genes, and proposed that crossing over bw X chromosomes can occur as well Morgan provided evidence for the linkage of x linked genes, and he proposed that crossing over and genetic recombination can indeed occur bw two x chromosomes the first direct evidence that different genes are physically located on the same chromosome what was the first direct evidence that different genes are physically located on the same chromosome the first direct evidence that different genes are physically located on the same chromosome the first direct evidence that different genes are physically located on the same chromosome came from the studies of Thomas Hunt Morgan in 1911 the first direct evidence that different genes are physically located on the same chromosome came from the implemented studies of Thomas Hunt Morgan that he conducted in 1911, these experiments are where the first pieces of evidence pointing towards genes being located on the same chromosome came from, genes being physically located on the same chromosome, this notion was first proposed and backed by evidence from the studies of Thomas Hunt Morgan Thomas Hunt Morgan investigated the inheritance patterns of different characters/traits that had been shown to follow an X-linked pattern of inheritance Morgan investigated the inheritance patterns of different characters/traits that had been proved and shown to follow an X-linked pattern of inheritance, follow an X-linked pattern of inheritance Morgan conducted a particular experiment involving three characters what were these three characters/traits that he studied t the three characters/traits that Morgan studied were body color, eye color, and wing length what were the parental crosses the parental crosses were wild type male flies, with the traits of gray body, red eyes, and long wings the dominant wild type traits, crossed and mated with females that had yellow bodies, white eyes, and miniature wings, all of the recessive traits within this species of fruit flies Morgan crossed wild type males with the dominant/wild type traits of grey bodies, red eyes, and long wings to females with the recessive traits of yellow bodies (the homozygous recessive allelic combination yy), white eyes (the homozygous recessive combination ww), and miniature wings (the homozygous recessive combination mm) the wild type alleles for these three genes coding for body color, eye color and wing length were the following: y+- the wild type allele coding for a gray body in the gene coding for body color w+- the wild type allele coding for red eyes in the gene coding for eye color m+- the wild type allele coding for long wings in the gene coding for wing length as expected, the phenotypes of the f1 generation produced from wild type males with the traits of gray bodies, red eyes, and long wings, and recessive females with homozygous recessive allelic combinations coding for the recessive traits of yellow bodies, white eyes, and miniature wings was the following: the phenotypes of the f1 generation were wild type females, female fruit flies displaying the wild type traits of gray bodies, red eyes, and long wings that the wild type male parental fruit flies in the parental generation had and in the f1 generation, all of the male fruit flies had the recessive traits of yellow bodies, white eyes, and miniature wings that the female parental flies with homozygous recessive allelic combinations coding for recessive traits had within the parental generation these results were expected and anticipated due to all three of these traits, body color, eye color, and wing length being x-linked meaning that in females, as long as they inherited one dominant allele for a trait, they would display the dominant trait that that dominant allele is coding for, even in the presence of a recessive allele however in males, there is hemizygosity, meaning that whatever allele they inherit in their single X chromosome inherited from their mother will determine the phenotypic trait that they display in this particular experiment the parental recessive females only had homozygous recessive allelic combinations of yy, ww, and mm on their X chromosome the male offspring of the f1 generation would inherit their x chromosome in their sex chromosome combination from their mother, and the y chromosome (that does not have genes affecting any of these traits) from their father therefore whatever alleles they inherited from their mother would determine the phenotypic traits coded for by the genes containing these alleles the only alleles that the males could inherit were recessive alleles, y coding for yellow body, w coding for white eyes, and m coding for miniature wings, bc the female parental flies had only homozygous recessive allelic combinations of yy, ww, and mm, that would result in the formation of gametes with recessive alleles only therefore the males within the f1 generation were guaranteed to inherit an x chromosome from their mother containing all recessive alleles, a y allele coding for yellow body, a w allele coding for white eyes, and an m allele coding for miniature wings, and the y allele would not have any genes encoding these traits, therefore there would be no other allele for these genes present within the male fruit fly offspring genomes to battle it out with the allele inherited from the mother therefore all of the male fruit flies due to their hemizygosity had the recessive traits of yellow bodies, white eyes, and miniature wings, matching the parental female fruit flies the linkage of these genes was revealed when the F1 fruit flies were mated to one another, and the F2 generation was examine recall that within the f1 generation all of the female fruit flies had the dominant traits of gray bodies, red eyes, and long wings (with presumably heterozygous allelic combinations for these x linked genes, where the dominant alleles coding for gray bodies, red eyes, and long wings won out) and all of the female fruit flies had the recessive traits of yellow bodies, white eyes, and miniature wings, all of their allelic combinations for these x linked genes consisting of one recessive allele within the f2 generation, instead of equal proportions of the 8 possible phenotypes being observed, there was a much higher proportion of the combinations of traits that were found in the parental generation observed within the f2 generation there were 758 total flies with gray bodies, red eyes, and long wings, mimicking and matching the phenotypic combinations of traits found within the male fruit flies of the parental generation, who also had the phenotypic combinations of gray bodies, red eyes, and long wings there were also 700 flies with the recessive traits of yellow bodies, white eyes, and miniature wings, mimicking and matching the combinations of phenotypic traits found within the parental generation within the female fruit flies, who all had the recessive traits of yellow bodies, white eyes, and miniature wings the combination of gray body, red eyes, and long wings was found in the males of the parental generation, in the male fruit flies of the f1 generation, and was the highest proportion of phenotypic combinations found amongst all the fruit flies produced in the f2 generation the combination the phenotypic combination of yellow body, white eyes, and miniature wings mimicked and matched the phenotypic combinations of the female fruit flies in the parental generation, and was the phenotypic combination found in the second highest proportion within the f2 generation what was Morgan's explanation for this higher proportion of parental combinations? Morgans explanation for this higher proportion of parental combinations was that all three of these genes coding for the traits of body color, eye color, and wing length are located on the x chromosome, and therefore tend to be transmitted together as a unit however in order to fully account for the data shown in figure 6.3 Morgan needed to explain why a significant proper in order to fully account for the data shown in figure 6.3 Morgan needed to explain why a significant proportion of the F2 generation had non parental combinations of alleles w why a significant proportion of the f2 generation had nonparental combinations of alleles along with the two parental phenotypes, there were 5 other phenotypes that did not appear within the f2 generaiton along with the two parental phenotypes found within the f2 generation that matched the phenotypic combinations found within the parental generation, there were 5 additional phenotypes, 5 additional phenotypic combinations, that did not match either of the phenotypic combinations found within the parental generation how did Morgan explain this data how did Morgan explain this date of high proportions of the 2 phenotypic combinations showcase and displayed within the parental generation occurring within the f2 generation, as well as the presence of 5 additional phenotypic combinations occurring within the f2 generation that did not match up with any phenotypic combinations found within the parental generation? Morgan considered the implemented and conducted studies of the Belgian cytologist Frans Alfons Janssens this Belgian cytologist Frans Alfons Janssens conducted experiments and studies in 1909 that Morgan referred to this Belgian cytologist observed chiasmata under the microscope, and then proposed that crossing over involves a physical exchange bw two homologous chromosomes he proposed that crossing over involves a physical exchange of chromosomal segments bw two homologous chromosomes Morgan shrewdly recognized and realized that crossing over bw homologous chromosomes, the physical exchange of chromosomal segments bw two homologous chromosomes, particularly the physical exchange of chromosomal segments bw two homologous X chromosomes was consistent with the data that he discovered within his f2 generation of fruit flies Morgan assumed that crossing over did not occur bw the x and Y chromosome, due to the x and Y chromosome not being homologous chromosomes and the phenomenon of crossing over and physically exchanging segments of chromosomes only occurring bw homologous chromosomes Morgan also assumed that these three fruit fly genes coding for body color, eye color, and wing length were not found on the Y chromosome, and therefore the y chromosome did not impact the traits that these genes code for with these ideas in mind, he hypothesized that the genes coding for body color, eye color, and wing length are all physically located and therefore linked on the same chromosome, namely the X chromosome therefore the alleles for all three of the characters that these genes code for, body color, eye color, and wing length are most likely to be inherited together, as the genes that these alleles are found within are physically located on the same chromosome, namely the x chromosome, so they are genetically linked and are therefore most likely to be inherited together due to the phenomenon of crossing over, the physical exchange of chromosomal segments bw homologous chromosomes, Morgan also proposed that the homologous x chromosomes within the female, the two homologous X chromosomes within the female sex chromosome combination of XX can undergo crossing over, where they physically exchange chromosomal segments with one another, and produce new, non parental combinations of alleles, and therefore through the new and nonparental combinations of alleles, produce new and non parental combinations of traits within the f2 generation in order to appreciate the proposals that Morgan made, let us simplify his data, and consider only two of the the three genes that he analyzed in his experiments: the gene coding for body color and the gene coding for eye color the following results were obtained in the f2 generation in the analysis of the traits of body color and eye color: 1159 offspring with gray body, red eyes- parental combination (matching the males of the parental generation, the wild type males with gray bodies and red eyes) 1017 offspring with yellow body, white eyes- parental combination (matching the females of the parental generation with the traits of yellow bodies and white eyes) 17 offspring with gray body and white eyes- recombination, non parental offspring 12 offspring with yellow body, red eyes- recombinant, non parental offspring how could Morgan's proposals account for this data the parental offspring with gray bodies and red eyes or yellow body and white eyes, these parental offspring with these particular phenotypic combinations were produced when no crossing over had occurred bw the two genes the gene coding for body color and eye color, no crossing over occurred bw these two genes, and thus the parental phenotypic combinations of gray bodies and red eyes and yellow bodies and white eyes were seen in the f2 generation, due to crossing over not occurring in the production of those offspring this was the most common situation, the most prevalent phenotypic combinations in the f2 generation were the parental combinations of gray bodies, red eyes and yellow bodies, white eyes however, crossing over could alter the pattern of alleles along each chromosome, and therefore account for the non parental offspring, the offspring in the f2 generation with recombinant and non parental combinations of phenotypic traits why were there relatively few nonparental and recombinant offspring within the f2 generation

nucleosome association

NUCLEOSOMES BECOME CLOSELY ASSOCIATED IN ORDER TO FORM A 30 NM FIBER in eukaryotic chromatin, nucleosomes associate with one another in order to form a more compact structure nucleosomes associate with one another in order to form a more compact structure, this more compact structure that are formed by nucleosomes closely associating is 30 NANOMETERS IN DIAMETER nucleosomes closely associate with one another in order to form 30 nm fibers (the diameter of these compact fibers is 30 nm) evidence for the packaging and close association of nucleosomes in order to further DNA compaction was obtained by Fritz Thomas in 1977 through his microscopy studies through Fritz Thomas's microscopy studies conducted and implemented in 1977, he was able to discover evidence for the packaging and close association of nucleosomes that occurs in order to further the process of DNA compaction, the creation of the more compact fiber with a 30 nm diameter he treated chromatin samples WITH A RESIN THAT REMOVED H1 the H1 histone, the linker histone that is responsible for binding to the linker region this resin technically removed the H1 histone, but what was truly responsible for the removal of the H1 histone from the linker region was the SALT CONCENTRATION the salt concentration was responsible for the proper removal of the H1 histone the linker histone from the linker region THERE WAS A MODERATE SALT SOLUTION A 100 MILLILMOLAR mM SALT SOLUTION THAT REMOVED THE H1 histone, the linker histone a solution with no added salt, no added NaCL did not manage to remove the H1 histone, the linker histone the samples were then observed underneath a microscope AT THESE MODERATE SALT CONCENTRATIONS- A 100 MILLIMOLAR CONCENTRATION SALT SOLUTION, when the DNA was exposed to this salt solution with this concentration of NaCL resulting in the proper removal of the H1 histone the linker histone, and these samples exposed to this moderately concentrated salt solution were placed under a microscope and analyzed, the chromatin exhibited the ESTABLISHED AND CLASSIC BEADS ON A STRING MORPHOLOGY the samples without added NaCl, the samples of DNA where the H1 histone the linker histone was not properly removed due to the lack of salt concentration, the BEADS on the string CLOSELY ASSOCIATED WITH ONE ANOTHER they closely associated with ONE ANOTHER INTO A MORE COMPACT CONFORMATION they did not subscribe to the beads on a string model these results suggested that nucleosomes are indeed packaged into a MORE COMPACT UNIT and the H1 histone, the linker histone has a role in the PACKAGING AND COMPACTION OF NUCLEOSOMES AND DNA the presence of the H1 histone, the linker histone has a role in regards to the compaction of nucleosomes and DNA, the close association of nucleosomes and the resulting compaction of DNA the specific role of the H1 protein remains fairly unclear recent implemented research has shown that the CORE HISTONES ALSO PLAY A KEY ROLE IN THE COMPACTION AND RELAXATION OF CHROMATIN the core histones the histones composing the octamer that the double stranded DNA molecule wraps itself around has been found to be responsible for the both the compaction and relaxing/decompaction of chromatin the nucleosome units closely associate and form the compact structure designated as the 30 nm fiber this 30 nm fiber SHORTENS THE TOTAL LENGHT OF THE DNA ANOTHER SEVENFOLD THE TOTAL LENGTH OF THE DNA IS SHORTENED ANOTHER SEVENFOLD DUE TO THE association of nucleosome units into a 30 nm fiber the structure of this 30 nm fiber has been difficult to pinpoint this is bc the structure of DNA may be dramatically and irreparably altered when the DNA is extracted from living cells, so researchers are unable to say for sure whether or not DNA takes on a specific form in this level of compaction where a 30 nm fiber is created there are many models for the 30 nm fiber, and what the 30 nm fiber looks like in cells there are two main classes for 30 nm fiber models one class is the SOLENOID CLASS: the solenoid model the solenoid model is one class of 30 nm fiber models THE SOLENOID MODEL proposes a structure of 30nm fiber models the solenoid model proposes the following specific structure, A HELICAL STRUCTURE in this helical structure, proposed by the solenoid model, there is CONTACT BW THE NUCLEOSOMES composing the 30 nm fiber in the helical structure proposed by the solenoid model, it is proposed that the NUCLEOSOMES are in contact with one another THERE IS CONTACT BW THE NUCLEOSOMES in the proposed solenoid model, creating a helical structure the contact bw the nucleosomes PRODUCES A SYMMETRICALLY COMPACT STRUCTURE WITHIN THE 30 NM FIBER the contact bw the nucleosomes that is proposed by the solenoid model produces a SYMMETRICALLY COMPACT HELICAL STRUCTURE the contact bw the nucleosomes that is proposed by the solenoid model produces a symmetrically compact helical structure this type of model, the solenoid model that proposes the 30 nm fiber structure consisting of visible contact bw the nucleosomes resulting in a symmetrical helical compact structure is favored by some researchers within the genetics field studying and proposing structures for the 30 nm fiber there however, is experimental data about the 30 nm fiber that suggests that THE 30 NM FIBER MAY NOT FORM SUCH A REGULAR STRUCTURE there is experimental data that contradicts the proposed solenoid model that proposes that there is contact bw the nucleosomes, and this contact results in the creation and maintenance of a symmetrical, helical, and compact structure there is evidence contradicting this proposed model there is an alternative zig zag model that has come to light due to experimental data this alternative zig zag model for the structure of the 30 nm fiber is advocated for and endorsed by Rachel Horowitz, Christopher Woodcock, and others how did this alternative zig zag model for the 30 nm fiber get proposed? this model that is advocated for by Rachel Horowitz, Christopher Woodcock, and others is based on a variety of techniques including: CRYOELECTRON MICROSCOPY- cryoelectron microscopy is electron microscopy that occurs at a v low temperature recall that cryoelectron microscopy is electron microscopy that occurs at a v low temperature according to this proposed zig zag model that was based on cryoelectron microscopy experimentation, electron microscopy at a v low temperature, the linker regions that are part of the composition of the 30 nm structure are VARIABLY BENT AND TWISTED the linker regions that are a part of the composition of the 30 nm structure are VARIABLY BENT AND TWISTED the linker regions that are part of the composition of the 30 nm fiber, are VARIABLY BENT AND TWISTED differentially bent and twisted there is little face to face contact occurring bw chromosomes v little face to face contact occurring bw chromosomes according to the proposed zig zag model that once again was developed due to cryoelectron microscopy, electron microscopy at a v low temperature at this level of compaction, the amount of compaction that is occurring within a 30 nm fibe, THE OVERALL PCITRUE OF CHROMATIN That develops from the proposed zig zag model is AN IRREGULAR FLUCTUATING 3 DIMENSIONAL ZIG ZAG STRUCTURE composed of stable nucleosome units these stable nucleosome units are connected by deformable linker regions so the chromatin model that develops out of the proposed zig zag model is one that is IRREGULAR, 3D, and has a zig zag structure the chromatin model that develops due to the proposed zig zag model is one that is irregular, 3D and has a zig zag structure this chromatin model is composed of STABLE NUCLEOSOME UNITS the nucleosome units composing this chromatin in this chromatin model are quite stable, in this zig zag model for chromatin, the nucleosome units composing this chromatin in this zig zag model are quite stable, in addition to forming an IRREGULAR 3D FLUCTUATING STRUCTURE in addition to forming an irregular 3D fluctuating structure, the nucleosome units are generally quite stable units quite stable individual units these stable individual nucleosome units are CONNECTED BY DEFORMABLE LINKER REGIONS these stable individual nucleosome units are CONNECTED BY DEFORMABLE LINKER REGIONS in 2005, Timothy Richmond and his colleagues were the first individuals to SOLVE THE CRYSTAL STRUCTURE OF A SEGMENT OF DNA CONTAINING MULTIPLE NUCLEOSOMES in 2005, Timothy Richmond and his colleagues were the first individuals to be able to solve and propose the correct model of the crystal structure of a segment of DNa that contains multiple nucleosomes Timothy Richmond and his colleagues were the first individuals to be able to solve and propose the correct model of the crystal structure of a segment of DNA containing a multitude of nucleosomes in this case they determined the crystal structure of a segment of DNA containing 4 nucleosomes the structure with 4 nucleosomes that Timothy Richmond and his four colleagues proposed, a crystal structure of a DNA segment with 4 nucleosomes, showcased a discovery their correct solution and model showcased that the LINKER DNA ZIGZAGS back and forth bw each nucleosome, the linker DNA region zigzags back and forth bw each individual nucleosome that the dna segment they are modeling is composed of this is a feature that is consistent with the zigzag proposed model

DNA and RNA structure- nucleotides and important features

Nucleotides are linked together in order to form a strand Nucleotides are linked together in order to form a single strand of DNA or RNA Nucleotides are linked together in order to form a single strand of DNA or RNA Nucletotides are linked together in order to form a single strand of DNA or RNA A strand of DNA or RNA contains and is composed of nucleotides that are covalently attached to one another in a linear fashion A strand of DNA ro RNA contains and is composed of nucleotides that are covalently attached to one another in a linear manner, in a linear formation A strand of DNA or RNA contains and is composed of nucleotides that are covalently attached to one another in a linear manner, in a linear formation There is a short strand of DNA with four nucleotides shown within the book A short strand of DNA with four nucleotides shown in the book There are a few structural features that should be examined and remembered There are a few structural features that should be examined and remembered There are a few structural features that should be examined and remembered There are a few structural features that should be examined and remembered There are a few structural features that should be examined and remembered First the linkage bw the nucleotides in this linear formation The linkage bw the nucleotides in this linear formation The linkage bw the nucleotides in this linear formation The linkage bw the nucleotides in this linear formation The linkage bw the nucleotdies in this linear formation involves AN ESTER BOND THERE IS AN ESTER BOND bw a phosphate group on one nucleotide and the sugar molecule on the adjacent nucleotide There is an ester bond bw a phosphate group on one nucleotide and the sugar molecule on the adjacent nucleotide There is an ester bond bw a phosphate group on one nucleotide and the sugar molecule on the adjacent nucleotide The linkage bw nucleotides involves an ester bond bw a phosphate group on one nucleotide and the sugar molecule on an adjacent nucleotide The linkage bw nucleotides involves an ester bond bw a phosphate group on one nucleotide and the sugar molecule on an adjacent nucleotide The linkage bw nucleotides involves an ester bond bw a phosphate group on one nucleotide and the sugar molecule on an adjacent nucleotide The linakge bw nucleotides involves an ester bond bw a phosphate group on one nucleotide and the sugar molecule, the pentose sugar on an adjacent nucleotide Another way of viewing this linkage bw nucleotides, the ester bond bw the phosphate group of one nucleotide and the pentose sugar of an adjacent nucleotide is to notice that A PHOSPHATE GROUP CONNECTS TWO SUGAR MOLECULES A PHOSPHATE GROUP CONNECTS TWO SUGAR MOLECULES A PHOSPHATE GROUP CONNECTS TWO SUGAR MOLECULES In a linear arrangement of nucleotides, a phosphate groups CONNECTS TWO SUGAR MOLECULES For this reason, the linkage in DNA or RNA strands is designated as a phosphodiester linkage For this reason, the linkage in DNA or RNA strands is designated as a phosphodiester linkage The linkage in DNA or RNA strands is designated as a phosphodiester linkage, due to a phosphate group linking the two sugars in the nucleotides' linear conformation The phosphates and the sugar molecules form the BACKNBONE OF A DNA OR RNA STRAND THE PHOSPHATES AND THE SUGAR MOLECULES FORM THE BACKBONE OF A DNA OR RNA STRAND IN THE LINEAR CONFORMATION OF THE NUCLEOTIDES The bases project from the back from the phosphate sugar backbone The phosphodiester bonds bw the phosphates and sugar molecules, the linking of two sugar molecules, of two pentose sugars by a phosphate group constitutes a structure of a chain of phosphate groups and sugars alternating with one another, constituting the sugar-phosphate backbone of a strand of DNA or RNA (which would depend upon the sugars being deoxyribose or ribose) The bases project from the phosphate sugar backbone of the strand of DNA or RNA The bases project from the phosphate sugar backbone of the strand of DNA or RNA The bases project from the phosphate sugar backbone of the strand of DNA or RNA The backbone, the phosphate sugar backbone of the strand of DNA or RNA is negatively charged, due to the presence of a negative charge on the phosphate sugar backbone The backbone, the sugar phosphate backbone of thestrand of DNA or RNA is negatively charged, due to the presence of a negative charge within each of the phosphate molecules, within each of the phosphate groups there is a negative charge, and that influences and results in the sugar phosphate backbone of a DNA or RNA strand having a negative charge A SECOND IMPORTANT STRCUTURAL FEATURE There is a second important structural feature This second important structural feature of the linear sequence of nucleotides constituting a strand of DNA or RNA is the ORIENTATION OF THE NUCLEOTIDES The orientiation of the nucleotides As mentioned, the carbon atoms in a sugar molecule are numbered in a particular way The carbon atoms in a sugar molecule are numbered in a v particular way The caron atoms in a sugar molecule are numbered in a v particular way The carbon atoms in a sugar molecule are numbered in a v particular way A phosphodiester linkage bw two nucleotides involves a phosphate attachment to the 5 prime carbon within one nucleotide and the 3 prime carbon in the other nucleotide The phosphate that is connecting the two nucleotides,the phosphate that is connecting the two sugars of two nucleotides is attached to the 5 prime carbon of the sugar of one of the nucleotides, and is attached to the 3 prime carbon of the sugar of the other nucleotide, this is how a phosphodiester bond links two nucleotides to one another, the phosphate group that links the two sugars together in order to form and constitute the sugar phosphate backbone, the phosphate group that links two nucleotides to one another attaches to the 5 prime carbon of one nucleotide's sugar, and the 3 prime carbon of the other nucleotide's sugar In a strand, in a single strand of dna or rna, all of the sugar molecules are oriented in the same direction The 5 prime carbon in every sugar molecule are located above the 3 prime carbon, the 5 prime carbon is somewhat adjacent on the left of the oxygen molecule within the pentose sugar though the 5 prime carbon in particular is not included within the ring/pentagon structure of the pentose sugar, and the 3 prime carbon is located below the 5 prime carbon and the 4 prime carbon Therefore a strand has a directionality based on the orientation of the sugar molecules within the nucleotides composing this strand by arranging themselves in a particular linear fashion In the figure show, the direction of the strand is 5 prime to 3 prime when going from top to bottom There is another critical aspect regarding the structure of DNA and RNA This critical aspect is that a single DNA or RNA strand contains a particular composition of bases, a particular and specific sequence of bases In the shown figure, the sequence of bases is thymine-adenine-cytosine-guanine The sequence of bases is thymine-adenine-cytosine-guanine The sequence of bases is thymine-adenine-cytosine-guanine This sequence of bases of nitrogenous bases is TACG Furthermore in order to showcase and identify the directionality of the strand, the strand should be abbreviated as 5'-TACG-3', indicating that the DNA strand goes in the direction of 5 prime to 3 prime when you are looking at this sequence from top to bottom The nucleotides within a strand are covalently bonded to one another The nucleotides within a strand are covalently bonded to one another The nucleotides within a strand are covalently bonded to one another The nucleotides within a strand are covalently bonded to one another And therefore, the sequence of bases within a DNA strand cannot shuffle around and become rearranged The sequence of bases within a DNA strand cannot shuffle around and become rearranged The sequence of bases within a DNA strand cannot shuffle around and become rearranged The sequence of nucleotide bases, the sequence of nitrogenous bases within a DNA strand cannot shuffle around and become rearranged Therefore the sequence of bases within a dna strand remains the same over time, throughout cellular division and dna replication, expect in rare cases when there is the potential occurrence of mutations

euploid

ORGANISM THAT ARE EUPLOID HAVE A CHROMOSOME NUMBER THAT IS AN EXACT MULTIPLE OF A CHROMOSOME SET organisms that are euploid have a chromosome number a total chromosome number that is an exact multiple of a chromosome set organisms that are euploid are euploid organisms that have a chromosome number, a total chromosome number that is an exact multiple of a chromosome set, this total chromosome number of this organism is an exact multiple of a chromosome set an example of euploid in drosophila melanogaster, a normal individual, a normal drosophila melanogaster organism has 8 chromosomes the species is a diploid species, having two sets of chromosomes, 2 sets of 4 chromosomes each an organism within this species with 8 total chromosomes, two sets of 4 chromosomes each is a euploid organism, because its total number of chromosomes is a multiple of a chromosome set of 4 chromosomes, it is that multiplied by 2 making for a total of 2 sets of 4 chromosomes, 8 chromosomes a normal fruit fly is designated as euploid because 8 chromosomes divided by 4 chromosomes per chromosomal set equals exactly 2 sets, the total number of chromosomes, 8, is a multiple of a chromosome set, containing 4 chromosomes, it is a chromosome set, containing 4 chromosomes, multiplied by 2 in order to result in 2 chromosomal sets, making this a diploid organism containing two sets of chromosomes one inherited paternally and the other maternally, for a total of 8 chromosomes ON RARE OCCASIONS AN ABNORMAL FRUIT FLY CAN BE PRODUCED on rare occasions an abnormal fruit fly can be produced with 12 chromosomes, containing 3 sets of chromosomes each containing 4 chromosomes per set

rna functions as the genetic material within some viruses

RNA indeed functions as the genetic material within some viruses RNA indeed functions as the genetic material RNA indeed functions as the genetic material within some viruses RNA indeed functions as the genetic material within some viruses RNA indeed functions as the genetic material within some viruses RNA indeed functions as the genetic material within some viruses RNA indeed functions as the genetic material within some viruses RNA functions as the genetic material in some viruses We know now that ARCAEA BACTERIA PROTISTS FUNGI PLANTS ANIMALS All use dna as their genetic material We know now that archaea, bacteria, protists, fungi, plants, and animals all use DNA as their genetic material We know now that archaea, bacteria, protists, fungi, plants, and animals all use DNA as their genetic material Archaea, bacteria, protists, fungi, plants, and animals all utilize DNA as their genetic material Archaea, bacteria, protists, fungi, plants, and animals all utilize DNA as their genetic material Archaea, bacteria, protists, fungi, plants, and animals all utilize DNA as their genetic material Viruses also have their own genetic material Viruses also have their own genetic material Viruses also have their own genetic material Hershey and Chase concluded from their experiments that this genetic material is DNA Hershey and Chase concluded from their experiments that the genetic material contained within viruses is indeed DNA they concluded that the genetic material that viruses have is indeed DNA In the case of the T2 bacteriophage, that is a verifiable and accurate conclusion, that the T2 bacteriophage contains In the case of the T2 bacteriophage that is a verifiable and accurate conclusion, that the T2 bacteriophage contains the genetic material DNA In the case of the T2 bacteriophage, it is a verifiable and plausible conclusion made by Hershey and Chase that the genetic material contained by the T2 bacteriophage is DNA In the case of the T2 bacteriophage it is a verifiable and plausible conclusion made by Hershey and Chase, that the genetic material contained by the T2 bacteriophage is indeed DNA However that isn't true for all viruses The T2 bacteriophage does indeed contain DNA as its genetic material, as was verified by the experiments of Hershey and Chase However, not all viruses contain DNA as their genetic material Many viruses utilize RNA instead of DNA as their genetic material Many viruses utilize RNA instead of DNA as their genetic material Many viruses utilize RNA instead of DNA as their genetic material Many viruses utilize RNA instead of DNA as their genetic material In 1956, Alfred Gierer and Gerhard Schramm isolated RNA from the tobacco mosaic virus (TMV) They isolated RNA from the tobacco mosaic virus, which is a virus that infects plant cells Tobacco mosaic virus is a virus that infects plant cells Tobacco mosaic virus is a virus that infects plant cells Tobacco mosaic virus is a virus that infects plant cells The aforementioned scientists isolated RNA from the tobacco mosaic virus The aforementioned scientists isolated RNA from the tobacco mosaic virus, which is a virus that infects plant cells When this purified RNA collected from the tobacco mosaic virus was applied to plant tissue, the plants developed the same types of lesions that occurred when they were exposed to fully intact and composite tobacco mosaic viruses Gierer and Schramm who had isolated this rna from the tobacco mosaic virus and then taken the purified rna collected from the virus and applied it to plant tissue, conclude to to the development of lesions on the plants that occurred when they were put into contact with completely intact tobacco mosaic virus, and apparently also specifically purified RNA extracted from the tobacco mosaic virus, concluded that the viral genome of TMV the viral genome of the tobacco mosaic virus is composed of RNA Since that time, many other viruses have been found to contain RNA as their genetic material We can compare the genetic compositions of a multitude of viruses, and see what functions as the genetic material of these viruses Examples of dna and rna containing viruses- this chart showcases how different viruses contain within them either rna or dna functioning as their genetic material, how this can differ and different viruses utilize different things as their genetic material Tomato bushy stunt virus The host of the tomato bushy stunt virus is the tomato, and the nucleic acid this virus contains is RNA Tobacco mosaic virus The tobacco mosaic virus, the host of the tobacco mosaic virus is tobacco, and the nucleic acid of the tobacco mosaic virus, the genetic material of the tobacco mosaic virus is RNA Influenza virus The influenza virus, the host of the influenza virus is humans The nucleic acid of the influenza virus is RNA HIV The host of HIV is humans The nucleic acid of HIV is RNA F2 The host of f2 is Escherichia coli The nucleic acid of f2 is RNA Qbeta The host of Qbeta is the bacterium Escherichia coli The nucleic acid of Qbeta is RNA Cauliflower mosaic virus The host of the cauliflower mosaic virus is cauliflower The nucleic acid of the cauliflower mosaic virus is DNA Herpesvirus The host of the herpes virus is humans The nucleic acid of herpesvirus is DNA SV40 The host of the SV40 virus is primates The nucleic acid of the SV40 virus is DNA Epstein-Barr virus The host of the Epstein-barr virus is DNA The nucleic acid of the Epstein-barr virus is DNA T2 The host of the T2 virus is Escherichia coli The nucleic acid of the Escherichia coli virus is DNA M13 The host of the M13 virus is Escherichia coli The nucleic acid of Escherichia coli is DNA

sequence complexity

SEQUENCE COMPLEXITY Refers to the NUMBER OF TIMES THAT A PARTICULAR BASE SEQUENCE appears throughout a genome Sequence complexity is a term that refers to the number of times a particular base sequence occurs throughout a genome, essentially how repetitive a particular base sequence is throughout a genome in contrast, unique or non repetitive sequences are genetic DNA sequences within the genome that are found ONCE OR A FEW TIMES WITHIN THE GENOME but certainly not often within the genome, they are found once or simply a few times within the genome, unique or nonrepetitive sequences moderately repetitive sequences MODERATELY REPETITIVE SEQUENCES are DNA sequences that are found A FEW HUNDRED TO SEVERAL THOUSAND TIMES IN THE GENOME moderately repetitive sequences are dna sequences that are found a few hundred to several thousand times within the genome moderately repetitive sequences are DNA sequences within the genome that are found a few hundred to several thousand times within the genome there are a few cases where moderately repetitive sequences are MULTIPLE COPIES OF THE SAME GENES moderately repetitive sequences can sometimes be multiple copies of the same genes moderately repetitive sequences can sometimes be multiple copies of the same genes an example of how moderately repetitive sequences can sometimes be multiple copies of the same genes THE GENES THAT ENCODE ribosomal RNA (rRNA) are found in many copies the genes that encode ribosomal RNA, rrna, are found in many copies RIBOSOMAL RNA is necessary for the function of ribosomes, they contribute/are responsible for the function of ribosomes cells therefore need a large amount of rrna in order to make the large amount of functional ribosomes that they require how is this accomplished? how do cells obtain the specific large amount of rrna that they require in order to make functional ribosomes? the cells obtain this large amount of rrrna that they require in order to make a particular, high number of functional ribosomes by having multiple copies of the gene (and therefore moderately repetitive sequences encoding this gene) to produce as much rrna as they need in order to produce the specific number of ribosomes that the cell requires another gene that is found in multiple copies, in the form of moderately repetitive sequences representing multiple copies of genes the histone genes ARE ALSO FOUND IN MULTIPLE COPIES why are histone genes found in multiple copies, why are there multiple copies of histone genes histone genes are found in multiple copies because A LARGE NUMBER OF HISTONE PROTEINS ARE REQUIRED FOR THE STRUCTURE OF CHROMATIN the structure of chromatin requires a large number of histone proteins, and therefore there are multiple copies of the histone gene coding for multiple copies of histones that the cell will require (it will require this high number of histones) in order to form the structure of chromatin there are other types of repetitive, moderately repetitive DNA sequences that are FUNCTIONALLY IMPORTANT an example of a different kind of moderately repetitive sequence moderately repetitive sequences may play role in the regulation of gene transcription and translation MODERATELY REPETITIVE SEQUENCES MAY PLAY A ROLE IN THE REGULATION OF GENE TRANSCRIPTION AND TRANSLATION moderately repetitive sequences may play a role in the regulation of the processes of gene transcription, and translation, processes that fall under the overarching concept of gene expression there are also some moderately repetitive sequences THAT DO NOT PLAY A FUNCTIONAL ROLE these moderately repetitive sequences DO NOT PLAY A FUNCTIONAL ROLE they ARE NOT FUNCTIONALLY IMPORTANT these moderately repetitive sequences do not play a functional role, they are not functionally important, and these moderately repetitive sequences that do not play a functional role and are not functionally important are DERIVED FROM TRANSPOSABLE ELEMENTS what are transposable elements- transposable elements are segments of DNA that are able to move within the genome transposable elements are segments of DNA within the genome that have the ability to move within the genome it belongs to highly repetitive sequences HIGHLY REPETITIVE SEQUENCES ARE DNA sequences THAT ARE FOUND TENS OF THOUSANDS OR EVEN MILLIONS OF TIMES THROUGHOUT THE GENOME highly repetitive sequences of DNA are DNA sequences that are found tens of thousands or even MILLIONS of times throughout the entirety of the genome each copy of a HIGHLY REPETITIVE SEQUENCE IS RELATIVELY SHORT a copy of a highly repetitive sequence is around a few nucleotides to several hundred in length the length of a highly repetitive sequence can span from a few nucleotides to several hundred nucleotides an example of highly repetitive sequences: highly repetitive sequences in humans: THE ALU FAMILY OF SEQUENCES FOUND IN HUMANS AND OTHER PRIMATES an example of repetitive sequences in humans and primates, a highly repetitive sequence in humans and primates is the ALU FAMILY OF SEQUENCES the ALU sequence is approximately 300 base pairs long this alu sequence derives its name from the observation made by researchers that this DNA sequence contains a site along its length of 300 base pairs, a site that is primed for cleavage by a RESTRICTION ENZYME KNOWN AS ALUI there is a site along every Alu gene somewhere along its 300 base pairs, that is primed for cleavage by a restriction enzyme the restriction enzyme that this site on the Alu gene along its 300 base pairs is primed for is designated as AluI the ALU sequences is PRESENT IN ABOUT 1 MILLION COPIES IN THE HUMAN GENOME within the human genome, there is a gene that is a highly repetitive sequence and is found in 1 million copies, that is the ALu gene the ALU GENE REPRESENTS ABOUT 10 PERCENT OF THE TOTAL HUMAN DNA this alu gene also occur every 5000 to 6000 base pairs this sequence is highly repetitive, it occurs about 1 million times in the human genome, it composes about 10 percent of the totality of human dna, and in the human genome it occurs every 5000 to 6000 base pairs evolutionary studies conducted on the Alu gene propose that the ALU gene sequence, this highly repetitive sequence that there are 1 million copies of in the human genome, making up 10 percent of the totality of human dna and occurring every 5000 to 6000 base pairs, arose 65 million years ago the alu gene arose 65 million years ago from A SECTION OF A SINGLE ANCESTRAL GENE DESIGNATED AS THE 7SL RNA gene since that time, this 7SL RNA gene has become a type of transposable element (a gene that can move throughout the genome) this 7SL RNA gene that the alu gene arose from 65 million years ago and descended from has become a transposable element, one that can move throughout the genome, and is specifically designated as a retroelemekt A RETROELEMENT IS A SEQUENCE that can be transcribed into RNA, copied into DNA, and inserted into the genome A RETROELEMENT IS A SEQUENCE THAT CAN BE TRANSCIRBED INTO RNA copied into DNA and inserted into the genome a retroelement can be transcribed into RNA, copied into DNA, and inserted into the genome A RETROELEMENT can be transcribed into RNA, copied into DNA, and inserted into the genome over the course of 65 million years since the Alu gene first arose and descended from the 7SL RNA sequence, the ALU sequence has been copied and INSERTED into the human genome a multitude of times, as it is a retroelemekt that can be transcribed into RNA, copied into DNA, and inserted into the genome, in order to achieve a totality of 1 million copies of the Alu gene within the human genome these highly repetitive sequences such as the ALU family ARE INTERSPERSED THROUGHOUT THE GENOME however there are some moderately and highly repetitive sequences that can be clustered together in the formation of A TANDEM ARRAY a tandem array is a collection, a conglomeration and cluster of moderately and highly repetitive sequences a tandem array is also designated as a tandem repeat recall that a tandem array is designated as a collection/conglomeration of moderately and highly repetitive dna sequences IN A TANDEM ARRAY, there is a v short nucleotide sequence that is repeated a multitude of times A VERY SHORT NUCLEOTIDE SEQUENCE IS REPEATED MULTIPLE TIMES, MANY TIMES IN A ROW an example of a tandem array occurs in drosophila looking at drosophila melanogaster, 19 percent of the chromosomal DNA found in the drosophila melanogaster genome is HIGHLY REPETITIVE DNA this highly repetitive dna that is found in 19% of the drosophila melanogaster genome is found in tandem arrays look at example in notes TANDEM ARRAYS that are composed of short sequences tend to be commonly found in the centromeric regions of chromosomes these are tandem arrays composed of short sequences, highly or moderately repetitive short sequences that are clustered together, and these types of tandom arrays consisting of v short sequences that are also highly repetitive and clustered together compose centromeric regions on chromosomes these centromeric regions on chromosomes that are composed of tandem arrays can be MORE THAN 1,000,000 BASE PAIRS IN LENGTH they can be more than a million base pairs in length why are highly repetitive sequences functionally significant whether these highly repetitive sequences have a significant function, serve an integral or important purpose is highly debated and controversial there are some experiments that have been conducted on the drosophila melanogaster fly species, and these implemented experiments indicate that the highly repetitive sequences composing 19 percent of the drosophila melanogaster genome, that is found in tandem arrays, may be responsible for the appropriate segregation of chromosomes during meiosis, that ensures that the gametes end up with the appropriate amount of genetic material it is not confirmed whether highly repetitive sequences play a role in the proper segregation of chromosomes during meiosis in other species, species other than drosophila melanogaster the sequences within highly repetitive dna, the particular base pairs/sequences composing these highly repetitive sequences vary as one moves from species to species the amount of highly repetitive dna within an organism compared to the amount of highly repetitive dna within a similar organism, an organism in a closely related species may also be dramatically different, such as in the case of the two closely related salamander species, plethodon larselli and plethodon richmondi, the former having a genome twice the size of the latter

robertsonian translocation

THE ABNORMAL CHROMOSOME THAT OCCURS IN FAMILIAL Down syndrome IS AN EXAMPLE OF A ROBERTSONIAN TRANSLOCAITON the abnormal chromosomes that occurs in familial Down syndrome is an example of a robertsonian translocation a robertsonian translocation what is a robertsonian translocation what is a robertsonian translocation a robertsonian translocation an example of a robertsonian translocation is the abnormal chromosome that occurs in familial Down syndrome an example of a robertsonian translocation is the abnormal chromosome that occurs when an individual has familial Down syndrome, the abnormal chromosome that is a fusion of the q arms of chromosome 14 and chromosome 21, that is there in the individual's genetic material in addition to one normal chromosome 14 and 2 normal chromosome 21's, which yields an excess of chromosome 21 genetic material, almost the equivalent of what is seen in a different form of down syndrome, one that comes about due to 3 copies of chromosome 21 this type of translocation, a robertsonian translocation was first described by Willam Robertson William Robertson first described this type of fusion in grasshoppers, a robertsonian translocation type of fusion, William Robertson was the first individual to describe this particular type of chromosomal fusion, and he first described this specific kind of chromosomal fusion in grasshoppers WHAT IS THIS TYPE OF TRANSLOCATION WHY IS IT UNIQUE a robertsonian translocation involves the BREAKS NEAR THE CENTROMERES OF TWO NONHOMOLOGOUS AND ACROCENTRIC CHROMOSOMES acrocentric chromosomes are chromosomes where the centromeres are located extremely off center acrocentric chromosomes are chromosomes where the centromeres are located extremely off center acrocentric chromosomes are chromosomes where the centromeres are located extremely off center acrocentric chromosomes are chromosomes where the centromeres are located extremely off center robertsonian translocation- this specific kind of translocation involves the following: a robertsonian translocation involves breaks occurring near the extremely off center centromeres of two nonhomologous acrocentric chromosomes there are breaks occurring near the centromeres, the extremely off center centromeres of two nonhomologous acrocentric chromosomes, so breaks occurring in two nonhomologous chromosomes, chromosomes that are not homologous to one another, with centromeres that are located extremely off center in the specific example given to us in the book, in figure 8.13, the LONG ARMS OF CHROMOSOMES 14 and 21 had fused the long, q arms of chromosomes 14 and 21 had fused, and this created one large single chromosome the two short arms of these chromosomes, the two short, p arms of these chromosomes were lost, when the two long q arms of chromosome 14 and 21 fused together with one another, creating one large chromosome THIS TYPE OF TRANSLOCATION BW TWO NONHOMOLOGOUS ACROCENTRIC CHROMOSOMES IS THE MOST COMMON TYPE OF CHROMOSOME REARRANGEMENT IN HUMANS the most common type of chromosome rearrangement In humans is a translocation bw two nonhomologous acrocentric chromosomes, this is the most common type of chromosome rearrangement that occurs in humans, a translocation occurring bw two nonhomologous acrocentric chromosomes, so a translocation occurring bw two chromosomes that are not homologous to one another and belong to different pairs of chromosomes and should definitely not be crossing over with one one another, these chromosomes whose pieces due to breaks are fusing together are also acrocentric, meaning that their centromeres are located extremely off center in the example given to us of a robertsonian translocation, there is a robertsonian translocation where the long q arms of chromosome 14 and chromosome 21 were fused together, and the two short p arms of chromosome 14 and chromosome 21 were lost when the two q arms the two long arms of chromosome 14 and 21 were fused together, resulting in the genetic content of the offspring, the zygote created from the gamete with a robertsonian translocation and a normal gamete having one fused chromosome consisting of the long q arms of chromosome 14 and 21, then two copies of chromosome 21, resulting in an excess amount of chromosome 21 material (again mimicking the other form that Down syndrome can manifest in, which is where there are 3 copies of chromosome 21, an amount of genetic material that is comparable to the 2 copies of chromosome one and the long q arm of another copy of chromosome 21 present in a fused chromosome that occurs in individuals with familial Down syndrome, down syndrome that is inherited due to one of the parents having translocations occur during their gamete formation that result in translocations in the offspring and phenotypic consequences in the offspring), and a deficiency in chromosome 14 genetic material, due to only one complete copy of chromosome 14 and then the long q arm of another copy of chromosome 14 present in the fused chromosome this type of translocation bw two nonhomologous acrocentric chromosomes such as chromosome 14 and 21 is the most common type of chromosome arrangement in humans this type of chromosome rearrangement in humans, the most common type of chromosome rearrangement, where there is translocation that occurs bw two nonhomologous and acrocentirc chromosomes, is the most common form of chromosome rearrangement in humans, and it OCCURS AT A FREQUENCY OF APPROXIMATELY 1 in 900 BIRTHS in humans, ROBERTSONIAN TRANSLOCATIONS INVOLVE ONLY THE ACROCENTRIC CHROMOSOMES 13, 14, 15, 21, and 22 in humans, robertsonian translocation only involve translocations bw nonhomologous acrocentric chromosomes and they specifically involves chromosomes 13, 14, 15, 21, and 21

eukaryotic cell division

THE COMMON AND EXPECTED OUTCOME OF EUKARYOTIC CELL DIVISION- MITOSIS the common and expected outcome of eukaryotic cell division/mitosis is the production of two genetically identical daughter cells, two genetically identical daughter cells that HAVE THE SAME NUMBER AND TYPES OF CHROMOSOMES AS THE ORIGINAL MOTHER CELL THEY PROLIFERATED FROM the two genetically identical daughter cells that develop from the original mother cell are genetically identical to one another and to their original mother cell in the way that they have the exact same number of chromosomes and the exact same types of chromosomes (and particularly exact same numbers of particular types of chromosomes) as the original mother cell that they proliferated from THE PROCESS that produces two daughter cells that are genetically identical to one another and the original mother cell they proliferated from is A REPLICATION AND DIVISION PROCESS a dna replication and dna and cell division process that is far more complex than the aforementioned and far simpler process of binary fission EUKARYOTIC CELLS THAT ARE DESTINED FOR CELLULAR DIVISION THAT ARE DESTINED TO UNDERGO THE PROCESS OF MITOSIS GO THROUGH A SERIES OF PHASES THAT CONSTITUTE ULTIMATELY THE CELL CYCLE, a process consisting of interphase (which in itself consists of G1, synthesis, and G2), mitosis, and cytokinesis there are 3 designations for phases: G for the gap phase S for the synthesis phase (synthesis of the genetic material, synthesis and replication of the DNA found within the original cell that will undergo proliferation) M for mitosis, the mitotic phase (where the synthesized and replicated DNA material will be sorted into two different portions of the original cell, and the original cell will divide and proliferate into two daughter cells why are the gap phases designated as such, designated as gap phases? they are designated as gap phases bc when researchers were conducting experiments on cells and microscopically examine and determine the cell cycle, these phases were thought to be fairly insignificant, and simply functioning as periods of time in bw the more important S phase and mitosis however, it was later discovered that both gap phases, G1 and G2 are integral and critical to the cell cycle, functioning in regards to restricting cell growth at a reasonable point, checking the replicated DNA and organelles for any particular errors, etc, and thus are important parts of the cell cycle that should be acknowledged the designation with their original term remained though, but it is understood that many important molecular changes occur during the G1 and G2 phases of the cell cycle TOGETHER THESE THREE AFOREMENTIONED PHASES: G1, S, and G2 constitute the conglomeration phase designated as interphase interphase is an overarching conglomeration of the G1, S, and G2 phase, these three phases together constitute the overarching portion of the cell cycle known as INTERPHASE there is another phase that a cell can enter into during the implementation of the cell cycle it is a phase that actively dividing and cells programmed to divide do not normally enter, but some cells that are designated to stop proliferating after a particular point, or are simply directed in some fashion to stop proliferating after a particular point will enter this phase of the cell cycle designated as G0 cells can remain permanently, or simply for extended periods of time within the G0 phase of the cell cycle a cell that enters into the G0 phase is either temporarily not proceeding through the remainder of the cell cycle (these are cells that are entering the G0 phase for a long period of time, but a finite amount of time nonetheless, so they will eventually exit the G0 phase, reenter the cell cycle, proceed through the cell cycle, and proliferate into genetically identical daughter cells) or they are cells that are permanently entering the G0 phase (they will never exit this phase and never reenter the cell cycle, they are not destined or directed to implement any more proliferation of genetically identical daughter cells these cells that permanently enter the G0 phase of the cell cycle and never go through the cell cycle or undergo cell division are designated as TERMINALLY DIFFERENTIATED CELLS permanently differentiated, set on a different path cells an example of these permanently differentiated cells that will enter the G0 phase and never proceed through the cell cycle and proliferate again are an ADULT MAMMALS NERVE CELLS after a particular point, once an adult mammal's brain is fully developed, there is no need for the nerve cells to keep proliferating as they are all fully formed, the nervous system is complete and the neural system systems of the body are set in place and functioning therefore these nerve cells within an adult mammal will become terminally differentiated, enter into the G0 phase of the cell cycle, and never again proceed through the phase and proliferate DURING THE G1 phase of interphase of the cell cycle the cell may prepare to undergo cellular/mitotic division depending on the cell type and the environment that the cell is found in (the environment and its characteristics that a cell exists within), a cell that is going through the G1 phase of interphase of the cell cycle can undergo particular molecular changes, or a multitude of molecular changes in order to prepare this cell for cellular division to occur examples of the molecular changes a cell may undergo during G1 in order to prepare the cell for cellular division THE SYNTHESIS OF PROTEINS particular proteins that will be needed in the process of cellular division and the implementation of this process will be formed during G1 in order to help prepare the cell to proceed through the cell cycle and cellular division once the G1 phase occurs and the cell has entered and gone through this phase, cell biologists designate the cell as having reached a restriction point, where it now will proceed through the rest of the cell cycle, undergo cellular division, and proliferate into two daughter cells at the end of G1 there is a restriction point that cells pass, where from this point onward, they will proceed through the cell cycle, undergo cellular division, and proliferate into two genetically identical daughter cells once the cell passes the restriction point of G1, the cell will proceed to S phase during S PHASE (the phase that the cell proceeds to once passing the restriction point at the end of G1 that commits the cell on the path of undergoing cellular division and proliferating into two genetically identical daughter cells), the genetic material within the cell is replicated, all of the DNA within these cells is replicated, all of the chromosomes within the cell containing all of the DNA of the cell, the cell's genome will be replicated after replication occurs, the two copies of each chromosome of a pair are designated as CHROMATIDS, they are two halves of a whole, forming chromosomes, considered components of the ultimate entity of a chromosome these chromatids are joined together at the CENTROMERE these two chromatids forming an individual chromosome are joined AT A REGION OF DNA KNOWN AND DESIGNATED AS THE CENTROMERE the two chromatids are joined at the centromere, a particular region of DNA and they form a unit designated as sister chromatids, they are sister chromatids as they are joined at the centromere to form a chromosome THE KINETOCHORE- this is a group of proteins that is bound to the centromere, this group of proteins designated as the kinetochore is bound to the centromere, and thus essentially located where the centromere is on every individual chromosome the proteins within the kinetochore, a group of proteins located by the centromere, which connects the two sister chromatids that come together in order to form a chromosome, also hold the sister chromatids together the proteins within the kinetochore also hold the sister chromatids together in order to form a single entity designated as a chromosome, composed of two sister chromatids that are genetically copies of one another the kinetochore is where the kinetochore microtubule connect during metaphase, so that when the kinetochore microtubules draw back towards opposing sides of the cell, they will draw the chromosomes with them, splitting the two sister chromatids which will now be designated as two individual chromosomes- CHROMOSOME SORTING DURING ANAPHASE kinetochores have a key role in that once the S phase has been implemented, a cell has twice as many sister chromatids as chromosomes in the G1 phase the number of sister chromatids after the S phase has been implemented is double the number of chromosomes we found in the cell during the G1 phase, due to all of the DNA within the cell being replicated during the S phase all of the DNA within the cell, all of the chromosomes within the cell were replicated forming sister chromatids, and therefore the number of sister chromatids within the cell after the S phase has been implemented is double the number of chromosomes found in the cell in the G1 phase, when the dna was not yet replicated a human cell in the G1 phase has 46 distinct and identifiable chromosomes in the G2 phase, as this cell has started to undergo the process of cellular division and begun to proceed through mitosis, the cell has 46 PAIRS OF SISTER CHROMATIDS< coming out to 92 sister chromatids, double the amount of chromosomes found within the cell during the G1 phase CHROMOSOME- this term was originally utilized in order to designate a distinct structure that is visible and observable through the utilization of a microscope CHROMOSOME MEANS COLORED BODY that can be observed and visible through a light microscope the term chromosome can refer to A PAIR OF SISTER CHROMATIDS DURING THE G2 PHASE after replication has occurred during the S phase it can also be referred to as a pair of sister chromatids during the early stages of the M phase, the mitotic phase where mitosis actually occurs it can also refer to the individual structures and entities found towards the end of the M phase, when mitosis is almost complete it can also refer to the individual entities found within the G1 phase during the G2 phase, this is what occurs to the cell when it is undergoing this phase: the cell accumulates all of the materials that it requires in order for nuclear and cellular division, in order for the nucleus to divide and for the cell itself to divide once it accumulates and gathers all of the material that it requires in order to undergo nuclear and cellular division, it will proceed to the next phase of the cell cycle mitosis

diploid

THE MAJORITY OF EUKARYOTIC SPECIES ARE DIPLOID the majority of eukaryotic species are diploid (containing two sets of chromosomes within each of their somatic cells) or they have a diploid phase to their life cycle diploid essentially means that within this diploid individual's somatic cells, there are 2 chromosomes for each type of chromosome, forming pairs within a human individual, they are diploid, having 2 sets of chromosomes, 1 set inherited from the mother, and the other set inherited paternally, from the father there are 23 pairs total within a human individual's somatic cells, and these 23 pairs demarcate 23 different types of chromosomes within each pair of chromosomes, there are 2 chromosomes, 2 for each kind of chromosome there are other diploid species these different diploid species have different numbers of chromosomes within their somatic cells the dog- 39 chromosomes per set, 2 sets making for a total of 78 chromosomes within their somatic cells the fruit fly- has 4 chromosomes per set, 2 sets making for a total of 8 chromosomes within their somatic cells the tomato- has 12 chromosomes per set, 2 sets, making for a total of 24 chromosomes when there is a diploid species, the members of a single pair of chromosomes are designated as homologs each individual type of chromosome contains two pairs each type of chromosome is found within a homologous pairing, 2 chromosomes to a pair an example to illustrate this 2 chromosome per type of chromosome pairing: a human somatic cell, within a human somatic cell, there are 2 copies of chromosome 1, 2 copies of chromosome 2, and so on and so forth within each pair of chromosome, the chromosome on the left is a homolog to the chromosome on the right, there are 2 homologous chromosomes to a pair, designating a type of chromosome in each pair of chromosomes, designating a particular type of chromosome, one chromosome is maternally inherited from the mother the homolog in this pair is paternally inherited from the father the two chromosomes within a homologous pair are NEARLY IDENTICAL IN SIZE the two chromosomes within a homologous pair are NEARLY IDENTICAL IN SIZE HAVE THE SAME BANDING PATTERN, as they have the same genes on them in the exact same order but perhaps different alleles of these genes coding for variants of the characteristic/trait the gene codes for CONTAIN A SIMILAR COMPOSITION OF GENETIC MATERIAL they have the same genetic material within them, as they contain the same genes coding for the same traits/characteristics BUT THEY MAY HAVE DIFFERENT ALLELES CODING FOR VARIANTS OF THAT TRAIT THAT THE GENE IS CODING FOR if a particular gene is found on one homolog of a pair, it will be found on the exact same location of the other homolog HOWEVER the homologs may carry different and distinct alleles of those genes, coding for variants of the trait that that particular gene is coding for (the gene they share) an example showcasing the principles described above: a gene in humans- OCA2 OCA2 is one of a few different genes that influences and impacts eye color the OCA2 gene is located on CHROMOSOME 15, this OCA2 gene comes in variants, a multitude of variants include: BROWN GREEN BLUE eyes in a person with brown eyes, one copy of chromosome 15 may carry the dominant allele of the OCA2 gene coding for brown eyes, which will overwhelm the other allele and cause the individual with this allelic combination to present with brown eyes its homolog could carry a recessive allele coding for blue eyes so the two homologs/copies of chromosome 15 both have the gene at the exact same location, specifically the OCA2 gene coding for eye color however, these two homologs/copies of chromosome 15 can have different alleles within their respective genes for eye color, perhaps one can have the dominant brown allele coding for the dominant variant of brown eyes, and one can have the recessive allele coding for the recessive variant of blue yes AT THE MOLECULAR LEVEL HOW SIMILAR ARE HOMOLOGOUS CHROMOSOMES bw homologous chromosomes, the SEQUENCE OF BASES OF ONE HOMOLOG the sequence of bases of one homologous chromosome of a pair tends to differ by LESS THAN 1 PERCENT compared to the sequence of nucleotide bases of the other homolog of the pair an example showcasing this genetic similarity bw homologues: THE DNA sequence of the maternally inherited chromosome 1, the chromosome 1 that you inherited from your mother would be be greater than 99 percent identical to the paternally inherited chromosome 1, the chromosome 1 that you inherited from your father, as these two chromosomes are homologous chromosomes, the same type of chromosome, and therefore are going to have fairly similar to identical gene sequences due to the fact that they are coding for the same genes the only variation you will find is within these gene sequences, where the two chromosomes may be coding for different variants of the trait that the gene is coding for, so there might be small difference in the genetic sequence of particular genes bw the two chromosomes that will occur and reflect that HOWEVER THE SEQUENCES ARE NOT IDENTICAL the slight differences that occur in the DNA sequences bw the two homologous chromosomes account for the allelic differences that are possible within genes, where there can be different alleles coding for variants of a trait that that gene codes for looking at eye color specifically EYE COLOR SPECIFICALLY AS ANE XAMPLE there is a slight difference within the DNA sequence encoding the OCA2 gene that distinguish brown, green, and blue alleles coding for brown, green, and blue eye color THE STRIKING SIMILARITIES BW HOMOLOGOUS CHROMOSOMES DOES NOT APPLY TO THE INDIVIDUAL AND DISTINCT SEX CHROMOSOMES X AND Y the sex chromosomes x and y differ in their genetic composition, as well as their size obviously two X chromosomes are homologous to one another and are identical/v similar in their genetic composition, coding for the exact same set of genes and perhaps only having genetic differences (differences in their genetic sequence) within these genes where they may have different alleles their DNA sequences are coding for that are coding for variants of the gene that both homologous chromosomes are coding for however bw X and Y, they may have some genes that are pseudoautosomally inherited and are found on both of them, but overall, the X and Y chromosomes are different in size (the X chromosome is much larger than the Y chromosome, this leads to the necessity of a Barr body of one X chromosome within all the somatic cells of a human female in order to balance out the amount of gene expression occurring naturally within the somatic cells of human males with the XY combination and human females with the XX) the X and Y chromosomes also differ in regards to their genetic composition, the X and Y chromosomes differ in regards to the genes that they have on the them, the genes that they share there may be some genes that are sex limited, some traits that are sex linked genes you will only find on the X chromosome, or only find within males, and therefore only on the Y chromosome, and therefore there will be different genes that are found on the X and Y chromosomes, and therefore they are not considered homologs to one another (though there are some areas of homology) there are particular genes found solely on the X chromosome that are not found on they Y chromosome there are particular genes on the Y chromosome that are not found on the X chromosome RECALL THAT THEY DO HAVE SHORT REGIONS OF HOMOLOGY BW THE TWO OF THEM BUT OVERALL THEY ARE FAIRLY DIFFERENT AND ARE NOT ULTIMATELY CONSIDERED HOMOLOGOUS TO ONE ANOTHER let us consider two HOMOLOGOUS CHROMOSOMES these two homologous chromosomes are coding for the same genes, they have the exact same genes on the exact same locations, as they are homologs of on another, they belong to a homologous pair of one type of chromosome) these two homologous chromosomes are labeled with 3 different genes AN INDIVIDUAL THAT IS CARRYING THESE TWO CHROMOSOMES THAT FORM A HOMOLOGOUS CHROMOSOMAL PAIR OF ONE TYPE OF CHROMOSOME would be homozygous for the dominant allele of gene A so for gene A, this individual is homozygous dominant bc it has the allelic combination AA, with one dominant allele A of gene A on one of the homologous chromosomes, and another dominant allele A of gene A on the other one of the homologous chromosomes for gene B, the individual with these two chromosomes containing these genes and forming a homologous pair would be heterozygous dominant for the second gene, gene B, bc it has the dominant allele B for gene B on one of its homologous chromosomes in this pair, and it has the recessive allele b for gene B on the other one of its homologous chromosomes in this pair, creating the heterozygous dominant allelic combination Bb for gene C, the individual is homozygous recessive for gene C, bc on both of its homologous chromosomes, it has the recessive allele c for Gene C on them, resulting in the homozygous recessive allelic combination cc

Punnett Square

THE MALE GAMETES GO ACROSS THE TOP OF THE PUNNET SQUARE THE FEMALE GAMETES GO ALONG THE SIDE OF THE PUNNET SQUARE

locus

THE PHYSICAL LOCATION OF A GENE THE PHYSICAL LOCATIONS OF GENES- LOCI the physical location of a gene, where a gene is located on a chromosome is the loci

balanced translocations

THE RECIPROCAL TRANSLOCATIONS THAT WE HAVE CONSIDERED THUS FAR ARE ALSO DESIGNATED AS BALANCED TRANSLOCATIONS the reciprocal translocations that we have analyzed so far are designated as balanced translocations, they are designated as balanced translocations because there is no loss or gain of genetic material, there is merely a rearrangement of the genetic material the total amount of genetic material is not altered in balanced translocations LIKE INVERSIONS balanced translocations, merely rearrangement of genetic material amongst chromosomes that does result in a change of the overall amount of genetic material,, does not result in any phenotypic consequences in the individual that has the balanced translocation or balanced translocations in their genetic material why does an individual with balanced translocations usually not experience phenotypic consequences, this is because the total amount of genetic material is not altered, the individual still has the normal amount of genetic material, all of the genetic material that it required IN A FEW CASES BALANCED TRANSLOCATIONS can result in position effects that are similar to those that can occur in inversions, where particular genes are impacted by chromosomal breakage, and therefore phenotypic consequences are seen in both inversion, where a chromosomal segment arises from a chromosomes being broken in two places and then flipped over to the opposite direction, there could be a gene or genes at the breaks required to separate out that chromosomal segment and flip it, and these genes can be affected by the break and result in phenotypic consequences in balanced translocations, translocations in general, but particularly balanced translocations, there are also chromosomal breaks resulting in chromosomal segments that are then fused together in different ways translocations can work in ways such as the chromosomal breakage resulting in chromosomal segments without telomeres, the chromosomal segments resulting from breakage do not have telomeres, which help cells to recognize where chromosomes naturally end, and prevent the addition of chromosomal dna to these established ends of the chromosomes with the lack of telomeres then the DNA repair enzymes, due to multiple breaks in multiple chromosomes may not be able to differentiate bw the different chromosomal segments, and which ones were originally paired with one another, and then may fuse two chromosomal segment back together that were not originally paired, resulting in translocations at these chromosomal breaks, there may be genes there that are impacted by these breaks and result in phenotypic effects there can also be crossing over bw nonhomologous chromosomes, and that can cause a reciprocal translocation to occur, and the breaking of these chromosomes into chromosomal segments in order for the crossing over of genetic material to occur can impact genes at the breakpoints and result in position effects and phenotypic consequences in the individual formed from a gamete where two nonhomologous chromosomes crossed over one another in addition to this, carriers of a reciprocal translocation are at risk of having offspring with an unbalanced translocation

nucleosome

THE REPEATING STRUCTURAL UNIT WITHIN EUKARYOTIC CHROMATIN is designated as the nucleosome the nucleosome is designated as the REPEATING STRUCTURAL UNIT WITHIN EUKARYOTIC CHROMATIN the repeating structural unit found within eukaryotic chromatin is designated as the nucleosome a double stranded segment of DNA wrapped around an octamer of histone proteins specifically, underneath the overarching definition of the nucleosome as the repeating structural unit found within eukaryotic chromatin, a nucleosome is DNA wrapped around an octamer (a conglomeration of 8 histones total, 4 different kinds of histones, two copies each) A NUCLEOSOME IS SPECIFICALLY DEFINED A SEGMENT OF DOUBLE STRANDED DNA WRAPPED AROUND AN OCTAMER OF HISTONES this double stranded dna segment is wrapped around an octamer of histones, and that is the repeating structural unit found in eukaryotic chromatin that is designated as a nucleosome the octamer that this segment of double stranded dna is wrapped around consists of 4 different types of histones: H2A, H2B, H3, and H4, w two copies of each histone, making for a total of 8 histones composing this octamer the double stranded dna is wrapped around these 8 histones composing an octamer THE DOUBLE STRANDED DNA LIES ON THE SURFACE OF THIS OCTAMER CONSISTING OF 8 HISTONES, 4 DIFFERENT TYPES OF HISTONES AND 2 COPIES EACH this double stranded dna lies on top of the histone octamer, then this double stranded dna makes 1.65 NEGATIVE SUPERHELICAL TURNS AROUND THIS HISTONE OCTAMER recall that the double stranded dna lies on top of the octamer consisting of 8 histones, 4 distinctive types of histones, 2 copies each, and then makes 1.65 NEGATIVE SUPERHELICAL TURNS AROUND THE HISTONE OCTAMER the double stranded dna lies on top of this histone octamer, then makes 1.65 NEGATIVE SUPERHELICAL TURNS AROUND THIS HISTONE OCTAMER THE AMOUNT OF DNA REQUIRED FOR THE DOUBLE STRANDED DNA TO PROPERLY WRAPPED AROUND THE HISTONE OCTAMER IS 146 to 147 base pairs the amount of dna required for the double stranded dna to properly wrap around the histone octamer is 146 TO 147 BASE PAIRS the amount of dna required for the double stranded dna to properly wrap around the histone octamer is 146- 147 base pairs AT ITS WIDEST POINT A NUCLEOSOME, DOUBLE STRANDED DNA WRAPPED AROUND AN OCTAMER OF HISTONES, where. it takes about 146 to 147 base pairs to wrap around this octamer of histones, is 11 nm in diameter AT ITS WIDEST POINT A NUCLEOSOME IS 11 NM IN DIAMETER the chromatin of eukaryotic cells contains a REPEATING PATTERN IN WHICH THE NUCLEOSOMES ARE CONNECTED BY LINKER REGIONS OF DNA the chromatin within eukaryotic cells contains a repeating pattern within this repeating pattern found within the chromatin of eukaryotic cells, the nucleosomes are connected by linker regions of DNA the nucleosomes in this repeating pattern found within the chromatin of eukaryotic cells are connected by LINKER REGIONS OF DNA these linker regions of DNA vary in length from 20 to 100 base pairs these linker regions of DNA linking nucleosomes to one another in a repeating pattern within the chromatin of eukaryotic cells vary in length from 20 to 100 BASE PAIRS it depends on the species and cell type, what the length of these linker regions is ranging from 20 to 100 BASE PAIRS what is the overall structure of connected nucleosomes the overall structure of connected nucleosomes RESEMBLES BEADS ON A STRING this structure of the beads on a string, these nucleosomes connected by repeating linker regions varying from 20 to 100 base pairs in length, SHORTENS THE LENGTH OF THE DNA MOLECULE ABOUT 7 FOLD the length of the dna molecule is shortened about sevenfold due to the structure represented by beads on a string, the nucleosomes attached to one another by repeating sequences of linker regions, each individually measuring 20 to 100 base pairs in length EACH OF THE HISTONE PROTEINS CONSISTS OF A GLOBULAR DOMAIN AND A FLEXIBLE CHARGED AMINO TERMINUS each of the histone proteins consists of a globular domain and a FLEXIBLE CHARGED AMINO TERMINUS THAT IS CALLED AN AMINO TERMINUS TAIL each of the histone proteins consists of these structures: a globular domain a flexible, charged amino terminus called an amino terminal tail a histone protein consists of a GLOBULAR DOMAIN AND A FLEXIBLE CHARGED AMINO TERMINUS THAT IS DESIGNATED AS AN AMINO ACID TAIL a histone protein consists of a globular domain and a flexible charged amino terminus that is designated as an amino acid tail a histone protein consists of the following structures: a GLOBULAR DOMAIN A FLEXIBLE CHARGED AMINO TERMINUS- AN AMINO ACID TAIL histone proteins are VERY BASIC PROTEINS why are histone proteins very basic proteins histone proteins are v basic proteins bc they contain a LARGE NUMBER OF POSITIVELY CHARGED LYSINE AND ARGININE AMINO ACIDS histone proteins are v basic proteins bc they consist of a LARGE NUMBER OF POSITIVELY CHARGED LYSINE AND ARGININE AMINO ACIDS histone proteins are v BASIC PROTEINS they are v basic proteins bc they CONSIST OF A LARGE NUMBER of POSITIVELY CHARGED LYSINE AND ARGININE AMINO ACIDS the ARGININES THAT COMPOSE HISTONE PROTEINS and contribute to why histone proteins are v basic, PLAY A MAJOR ROLE IN TERMS OF BINDING TO DNA the arginines play an integral role in the binding of histone proteins to DNA arginines that compose histone proteins, ARGININES That are part of the conglomeration of lysine and arginine amino acids that compose and constitute histone proteins, arginines specifically FORM ELECTROSTATIC AND HYDROGEN BONDING INTERACTIONS WITH THE PHOSPHATE GROUPS ALONG THE DNA BACKBONE the arginines found within histone proteins form electrostatic and hydrogen bonding interactions with the phosphate groups located along the DNA backbone the arginines found within histone proteins form ELECTROSTATIC and HYDROGEN BONDING INTERACTIONS with the phosphate groups located along the DNA backbone, this is how these arginines within histone proteins facilitate and are integral to the process of the histone protein binding to the dna the OCTAMER OF HISTONES CONTAINS TWO MOLECULES OF EACH OF THE FOUR FOLLOWING DIFFERENT HISTONE PROTEINS: H2A H2B H3 H4 these are the four different proteins composing an octamer, found in two copies each, making for 8 proteins composing a single histone octamer THESE ABOVE HISTONES ARE CALLED THE CORE HISTONES in 1997, Timothy Richmond and his colleagues determined the structure of a nucleosome through the implementation of X-ray crystallography there is another histone designated as H1 this H1 histone protein is found IN MOST EUKARYOTIC CELLS AND IS CALLED THE LINKER HISTONE THE H1 histone protein is found in the majority of eukaryotic cells, and the H1 histone protein is also given the designation as a linker histone THIS HISTONE PROTEIN H1, designated as the linker histone, binds to the DNA in the LINKER REGION BW NUCLEOSOMES (that is why it is designated as the linker histone) the histone protein H1, designated as the linker histone, binds to the DNA in the LINKER REGION FOUND BW NUCLEOSOMES AND ASSISTS IN COMPACTING ADJACENT NUCLEOSOMES the histone protein H1, also known as the linker histone, binds to the DNA in the linker regions bw nucleosomes and assists in the further compaction of adjacent nucleosomes THE LINKER HISTONES ARE LESS TIGHTLY BOUND TO THE DNA than are the core histones THE LINKER HISTONES ARE LESS TIGHTLY BOUND TO THE DNA THAN ARE THE CORE HISTONES THE LINKER HISTONES ARE LESS TIGHTLY BOUND TO THE DNA THAN ARE CORE HISTONES in addition to the role that the histone protein H1 plays in binding to the dna in linker regions bw nucleosomes and assisting in the further compaction of nucleosomes, there are NON HISTONE PROTEINS there are non histone proteins in addition to the histone H1 that are bound to the linker regions bw nucleosomes, and these NONHISTONE PROTEINS play a role in the ORGANIZATION AND COMPACTION OF CHROMOSOMES these nonhistone proteins also bound to the linker regions bw nucleosomes in addition to the H1 histone that is also bound there assist in the SORTING AND COMPACTION/FOLDING OF CHROMOSOMES the presence of these nonhistone proteins in the linker regions bw nucleosomes may also affect the expression of genes located near these nonhistone proteins

additional sequences in chromosomal DNA

THERE ARE OTHER SEQUENCES IN CHROMOSOMAL DNA THAT INFLUENCE DNA REPLICATION, GENE TRANSCRIPTION AND CHROMOSOME STRUCTURE there are other sequences in chromosomal DNA that influence DNA REPLICATION- the replication of DNA GENE TRANSCRIPTION- the transcription of genes that encode proteins to mRNA and then proteins CHROMOSOME STRUCTURE - the structure, the physical structure of chromosomes is influenced as well by particular and specific DNA sequences BACTERIAL CHROMOSOMES HAVE ONE ORIGIN OF REPLICATION bacterial chromosomes have one origin of replication this origin of replication, recalling that bacterial chromosomes simply contain one origin of replication, is usually a nucleotide sequence a DNA sequence that is a few hundred nucleotides in length the origin of replication in a bacterial chromosome is usually a few hundred nucleotides in length this nucleotide sequence functions as AN INITATION SITE FOR THE ASSEMBLY OF SEVERAL PROTEINS THAT ARE INTEGRAL AND REQUIRED FOR THE PROCESS OF DNA REPLICATION the nucleotide sequence that is the bacterial chromosome's origin of replication functions as an initiation site, an initiation site for the synthesis of a multitude of proteins that are integral to DNA replication repetitive sequences of DNA a variety, a multitude of repetitive sequences have been identified in many bacterial species a variety of repetitive sequences have been identified in many bacterial species A VARIETY OF REPETITIVE SEQUENCES OF DNA these repetitive sequences of DNA found within bacterial species are found in MULTIPLE COPIES AND ARE USUALLY interspersed with the intergenic regions occurring throughout the entirety of the bacterial chromosome repetitive sequences found in bacterial species are usually on bacterial chromosomes, interspersed with intergenic regions nucleotide sequences bw genes that are not transcribed repetitive sequences may play a role in a variety, in a multitude of of genetic processes repetitive sequences may play a role in a variety of genetic processes, including: DNA folding- the folding and compaction of DNA DNA replication- the replication of DNA that occurs during the synthesis phase prior to mitosis and meiosis I and ii gene regulation- how much a gene is unregulated or down regulated genetic recombination- genetic sequences being swapped with eachother, genetic material being exchanged during the formation of a synapse during prophase I of meiosis I in order to bring about genetic variation and phenotypic variation there are some repetitive sequences that are transposable elements some repetitive sequences are TRANSPOSABLE ELEMENTS some repetitive sequences are TRANSPOSABLE ELEMENTS what does it mean that repetitive sequences can also be transposable elements serve as transposable elements what this means is that these repetitive sequences of DNA can move throughout the genome, can shift throughout the genome

topoisomerase I

THIS IS A SECOND TYPE OF ENZYME this enzyme of topoisomerase I is responsible for and capable of relaxing negative supercoils this enzyme topoisomerase I can bind to a negatively supercoiled region of DNA, and then this enzyme topoisomerase I can introduce a break into one of the DNA strands in the DNA region that it is focusing on, the negatively supercoiled region that it is now bound to so the topoisomerase I enzyme is able to relax negative supercoils the way it goes about doing this, the way topoisomerase I goes about relaxing negative supercoils, is that this enzyme TOPOISOMERASE I binds to a negatively supercoiled region of DNA and introduces a break in one of the DNA strands of this negatively supercoiled region of DNA that it has bound to once this DNA strand in the negatively coiled region that topoisomerase I bound to is broken by topoisomerase I, the DNA molecule is able to ROTATE in order to RELIEVE THE TENSION caused by negative supercoiling due to the broken DNA strand in the negatively supercoiled region, the DNA molecule is able to rotate in order to relieve the built up tension that occurred due to the negative supercoiling the rotation of the DNA in order to relax negative supercoiling occurs due to the DNA strand in a negatively supercoiled region being broken by topoisomerase I, the enzyme that is bound to that region IT RELIEVES THE TENSION CAUSED BY SUPERCOILING the broken strand is then resealed, the DNA strand in the formerly negatively supercoiled region that was broken by topoisomerase I is now resealed the COMPETING ACTIONS OF DNA GYRASE/TOPOISOMERASE II AND TOPOISOMERASE I GOVERN THE OVERALL SUPERCOILING OF THE BACTERIAL DNA the competing and competitive actions of DNA gyrase/topoisomerase II and topoisomerase I the former, DNA gyrase/topoisomerase II forming negative supercoils and relaxing positive supercoils, and the latter, the topoisomerase I, relaxing negative supercoils govern the overall supercoiling that occurs in the bacterial DNA THE ABILITY OF GYRASE THE ABILITY OF DNA GYRASE TO INTRODUCE NEGATIVE SUPERCOILS INTO THE DNA IS CRITICAL IN ORDER FOR THE BACTERIA TO SURVIVE the ability of dna gyrase to introduce negative supercoils into dna, particularly bacterial chromosomal dna, is critical for the bacterial cells to survive in order for the bacterial cells to survive, they require the ability of dna gyrase to introduce negative supercoils into the bacterial chromosomal dna bacteria are able to survive due to dna gyrase and its function of introducing negative supercoils into bacterial dna therefore extensive research has been done investigating drugs that specifically block bacterial dna gyrase's function of introducing negative supercoils into bacterial chromosomal dna (which allows the bacterial chromosomal dna as well as bacterial cells to survive) researching and discovering drugs that are responsible for mitigating the function of bacterial dna gyrase help to alleviate or cure diseases that are caused by bacteria the discovery of drugs that block the function of dna gyrase, which is to introduce negative supercoils into bacterial chromosomal dna, which allows both the bacterial chromosomal dna and the bacterial cells containing them to survive, ensures that we have drugs that are able to block this extremely important function of dna gyrase and therefore cure or alleviate diseases caused by bacteria, as the enzyme responsible for allowing them to subsist and consistently live, allowing the bacterial cells to proliferate and remain alive, is rendered nonfunctional by said drugs, and therefore results in the mitigation of the proliferation of the bacterial cells of the disease you are targeting THERE ARE TWO MAIN CLASSES OF DRUGS that are responsible for inhibiting the function of dna gyrase: QUINOLONES COUMARINS quinolone and coumarins are the two main classes of drugs that are responsible for inhibiting the function of dna gyrase THESE TWO AFOREMENTIONED CLASSES OF DRUGS QUINOLONES AND COUMARINS are responsible for inhibiting the function of dna gyrase and OTHER BACTERIAL TOPOISOMERASES these two classes of drugs are able to inhibit the function of dna gyrase and other bacterial topoisomerases responsible for introducing negative supercoils into or relaxing positive supercoils in bacterial chromosomal dna, AND THEREFORE BLOCK BACTERIAL CELL GROWTH these drugs responsible for inhibiting the function of dna gyrase and other bacterial topoisomerases are NOT ABLE TO INHIBIT THE FUNCTION OF EUKARYOTIC TOPOISOMERASES this is bc the eukaryotic topoisomerases are structurally different from their bacterial counterparts of bacterial dna gyrase and bacterial topoisomerases, and therefore these classes of drugs quinolones and coumarins targeting and inhibiting the function of bacterial dna gyrase and other bacterial topoisomerases are unable to target these enzyme's structurally different eukaryotic counterparts, that would require different kinds of specific targeting drugs in order to inhibit their function THIS FINDING of quinolones and coumarins being classes of drugs that are able to inhibit the function of dna gyrase and other bacterial topoisomerases has assisted with the production of a multitude of drugs that have IMPORTANT BACTERIAL APPLICATIONS meaning important applications in inhibiting the proliferation of bacterial cells of particular diseases and therefore inhibiting the proliferation of bacterial diseases an example of a drug that has been created to stop the proliferation of bacterial cells of a particular bacterial disease due to the knowledge that the particular classes of drugs quinolones and coumarins are able to inhibit the function of dna gyrase and other bacterial topoisomerases, the inhibiting of which will stop bacterial cell proliferation and therefore stop the proliferation of bacterial diseases is CIPROFLOXACIN the brand name of this drug is Cipro, and this drug is used to treat a wide spectrum of bacterial diseases, due to its ability to inhibit the function of dna gyrase and other bacterial topoisomerases a disease that it is able to inhibit and mitigate is anthrax amongst others

translocations

TRANSLOCATIONS INVOLVE EXCHANGES BW DIFFERENT CHROMOSOMES translocations involve exchanges bw different chromosomes there is another type of chromosomal rearrangement this additional type of chromosomal rearrangement is a translocation in which a piece of one chromosome is taking from that chromosome and attached to a different chromosome, or attached to a different part of the chromosome that it detached from eukaryotic chromosomes have telomeres eukaryotic chromosomes have telomeres, these telomeres tend to prevent translocations from occurring eukaryotic chromosomes have telomeres, and these telomeres tend to prevent translocations from occuring eukaryotic chromosomes have telomeres and these telomeres tend to prevent translocations from occurring TELOMERES what are telomeres telomeres are specialized repeated sequences of DNA telomeres are specialized repeated sequences of DNA THAT ARE FOUND AT THE ENDS OF NORMAL CHROMOSOMES, PARTICULARLY IN NORMAL EUKARYOTIC CHROMOSOMES telomeres are specialized repeated sequences of DNA that are found at the ends of normal chromosomes, particularly in normal eukaryotic chromosomes telomeres allow cells to identify where a chromosome ends and prevent the attachment of chromosomal DNA to the natural ends of a chromosome TELOMERS ALLOW CELLS to identify where a chromosome ends, and prevent the attachment of chromosomal dna to the natural ends of a chromosome telomeres allow cells to identify the locations where a chromosome ends, and then prevent the attachment of chromosomal dna to the natural and identified ends of the chromosomes if cells are exposed to agents that cause chromosomes to break, the broken ends lack telomeres and are said to be reactive if cells are exposed to agents that cause chromosomes to break, the broken ends lack telomeres and are said to be reactive eukaryotic chromosomes have telomeres eukaryotic chromosomes have telomeres that tend to prevent translocations from occurring eukaryotic chromosomes have telomeres that tend to prevent translocations those specific kinds of chromosomal aberrations from occurring TELOMERES ARE SPECIALIZED REPEATED SEQUENCES OF DNA telomeres are specialized repeated sequences of DNA telomeres ARE SPECIALIZED REPEATED SEQUENCES OF DNA telomeres are specialized repeated sequences of DNA and they are specialized repeated sequences of DNA that are found at the ends of normal chromosomes, they are specialized repeated sequences of DNA that are found at the ends of normal eukaryotic chromosomes TLEOMERES these specialized repeated sequences of DNA that are found at the ends of normal eukaryotic chromosomes help cells to identify where a chromosome ends, and due to telomeres, these specialized repetitive sequences of DNA found at the end of normal eukaryotic chromosomes allowing cells to identify the ends of chromosomes, they ensure that chromosomal dna does not attach to the natural ends of the eukaryotic chromosomes that they are on, telomeres as specialized repeated sequences located on the ends of normal eukaryotic chromosomes allow cells to identify where chromosomes end, and therefore prevent the attachment of chromosomal DNA to the natural ends of chromosomes HOWEVER if cells are exposed to agents that cause chromosomes to break, the broken ends LACK TELOMERES AND ARE SAID TO BE REACTIVE if cells are exposed to agents that cause chromosomes to break, the broken ends of the chromosomes resulting from the chromosome breakage lack telomeres at their ends and are said to be reactive what does it mean that these broken ends of chromosomes do not have telomeres and are now reactive? THIS MEANS THAT A REACTIVE END OF A CHROMOSOME READILY BINDS TO ANOTHER REACTIVE END OF A CHROMOSOME if a single chromosome break occurs, DNA repair enzymes will usually recognize the two reactive, broken ends that are created and join these two reactive ends back together, if there is a single chromosome break and two reactive ends to stitch back together in this scenario where there is one break and therefore two resulting broken chromosome ends that are both reactive due to lack of telomeres and can be stitched back together, they are stitched back together by DNA repair enzymes and the chromosomal repair is complete, the chromosome is repaired properly however, if multiple chromosomes are broken, the reactive ends may be joined incorrectly however, if multiple chromosomes are broken, the reactive ends may be joined incorrectly to one another, bc the DNA repair enzymes may not be able to recognize which reactive end pairs with another, as there are so many due to multiple breaks, multiple chromosomes breaking and resulting in a multitude of reactive ends that need to be stitched back together in this scenario of multiple chromosomes being broken, multiple reactive ends needing to be stitched back together, and the DNA repair enzymes perhaps not being able to adequately differentiate bw reactive ends, and which ones should go together, abnormal chromosomes may be created by the stitching of non paired reactive ends together with one another this mechanism of new abnormal chromosomes being created due to incorrect repairing of reactive ends, pairing nonpaired reactive ends together in stitching chromosomes back together, and creating new abnormal chromosomes, this is one mechanism that can cause reciprocal translocations to occur

the discovery of the double helix structure

The discovery of the double helix feature There were a few key events that led to the discovery of the double helix structure There were a few key events that led to the discovery of the double helix structure There were a few key events that led to the discovery of the double helix structure There were a few key events that led to the discovery of the double helix structure There was a major discovery in molecular genetics that was made in 1953 by James Watson and Francis Crick There was a major discovery in molecular genetic made in 1953 by James Watson and Francis Crick At that time DNA was already known to be composed of nucleotides At that time of the discovery made by Watson and crick in 1953 A major discovery in molecular genetics was made in 1953 A major discovery in molecular genetics was made in 1953 A major discovery in molecular genetics was made in 1953 A major discovery in molecular genetics was made in 1953 What was the major discovery At the time of this discovery, DNA was already known to be composed of nucleotides At the time of this discovery DNA was already known to be composed of nucleotides However it was not fully understood or understood how the nucleotiddes are bonded together in order to form the structure of DNA Watson and Crick committed themselves to determining the structure of DNA bc they felt this knowledge was needed in order to understand the functioning of genes Watson and crick committed themselves to determining the structure of DNA because they felt that understanding and comprehending the structure of DNA was integral to comprehension of the functioning of genes They felt that understanding and comprehending the structure of dna was integral and critical to the comprehension of how in the world genes functions There were other researchers rosalid franklin and mauric wilkins who also believed that it was extremely important to understand and comprehend the structure of dna, they believed that understanding and comprehending the structure of dna was integral to understanding the function of genes In the early 1950's linus pauling proposed that regions of proteins are able to fold into a secondary structure known as an alpha helix In the early 1950s linus pauling proposed that regions of proteins are able to fold themselves into a secondary structure known as an alpha helix He proposed that regions of proteins are able to fold themselves into a secondary structure designated as an alpha helix In order to elucidate and establish this structure, linus pauling constructed large models by linking together simplistic ball and stick units By carefully scaling the objects in his models, he could visualize if atoms fit together properly in a complex and complicated 3 dimesnional structure He carefully scaled the objects in the models he constructed of ball and stick models linked together, so that he could verifiably visualize if the atoms fit together with one another in a complex and complicated 3 dimensional strcutrue Is this approach still utilized today, of linking together ball and stick models? Yes this approach is still utilized today, however, researchers today construct their 3 dimensional models on computers Watson and crick also utilized and implemented a ball and stick approach in order to solve the structure of the DNA helix, in order to understand where all of the components of the two strands of DNA intertwined and connected and fit to form a comprehensive structure There was a second important development that led to the elucidation of the double helix There was a second important development that led to the elucidation of the double helix The second important development that led to the elucidation of the double helix was X ray diffraction data When a purified substance, such as DNA is subjected to X rays, it produces a well defined diffraction pattern When a purified substance, such as DNA is subjected to x rays, it produces a well defined diffraction pattern When a purified substance, such as DNA is subjected to x rays, it produces a defined diffraction pattern An interpretation of the diffraction pattern, through the utilization of mathematical theory, can ultimately provide information to us concerning the structure of the molecule An interpretation of the diffraction pattern given off due to the purified DNA being subjected to x rays and producing a diffraction pattern, an interpretation of the presented diffraction pattern utilizing mathematical theory can ultimately provide information concerning the particular structure of the molecule the interpretation of the diffraction pattern through the utilization of mathematical theory Rosalind Franklin worked in the same laboratory as Maurice Wilkins Rosalid franklin utilized the technique of x ray diffraction in order to study wet dna fibers Rosalind franklin utilized the technique of x ray diffraction in order to study wet dna fibers Rosalid franklin utilized the technique of x ray diffraction in order to study wet dna fibers Franklin made marked advances in x ray diffraction techniques while she worked with dna and analyzed these wet dna fibers Franklin made marked and substantial advances in regards to the process and technique of x ray diffraction as she utilized this process in order to analyze and study wet dna fibers Franklin adjusted her equipment so that she could produce an extremely fine beam of x rays She adjusted her equipment so that she could produce an extremely fine beam of x rays She also extracted finer DNA fibers than ever before, and arranged these finer than ever before dna fibers that she extracted in parallel bundles She extracted dna that was finer than ever before, and arranged these finer than ever before extracted dna fibers in parallel bundles Franklin also studied the fibers' reactions to humid conditions The diffraction pattern of franklin's dna fibers The pattern show, the diffraction pattern of franklin's dna fibers showcases and suggests that there are several structural features of dna The diffraction pattern that Rosalind franklin developed suggested that there were several key components to the structure of dna First, it was consistent with a helical structure The diffraction pattern that Rosalind franklin developed was consistent with a helical structure Second, the diameter of the helical structure was far too wide to be only a single stranded helix, suggesting that there was more than one strand forming this helix, due to the diameter being far too wide, the diameter of the helical structure being far too wide to be formed by a single strand, suggesting the presence of multiple strands forming this helix with the wide diameter The diffraction pattern that Rosalind franklin developed also indicated that the helix contains about 10 base pairs per complete turn of the helix The helix contains about 10 base pairs per turn

molecular structure of dna

The molecular structure of the dna double helix has several key feature s The molecular structure of the dna double helix has several key features The general structural features of the double helix In a dna double helix, two dna strands are twisted together around a common axis In a dna double helix two dna strands are twisted together around a common axis In a dna double helix two dna strands are twisted together around a common axis in order to form a structure that resembles a spiral staircase In a dna double helix two dna strands are twisted together around a common axis in order to form a structure that resembles a spiral staircase This double stranded structure is stabilized by base pairs This double stranded structure in the conformation of a spiral staircase due to the twisting of the two dna strands around a common axis, the double stranded structure is stabilized by base pairs Base pairs are pairs of bases in opposite strands that are hydrogen bonded to one another Counting the bases, if you move past 10 base pairs, then you have gone 360 degrees around the dna backbone, meaning you have completed one turn The linear distance of a complete turn consisting of 10 base pairs is 3.4 nm Each base pair transverses 0.34 nm The linear distance of a complete turn consisting of 10 base pairs is 3.4 nm A section of the dna double helix consisting of 10 base pairs constitutes a single turn, as following along a dna segment of 10 base pairs will result in a 360 degree rotation around the dna double helix backbone The linear distance of a complete turn consisting of 10 base pairs is 3.4 nm Each base pair, each individual base pairs constitutes and transverses a length of 0.37 nm What is a distinguishing feature of the hydrogen bonding bw base pairs A distinguishing feature of the hydrogen bonding bw base pairs is its specificity A distinguishing feature of the hydrogen bonding bw base pairs is its specificity An adenine base in one strand hydrogen bonds with a thymine base in the opposite strand, or guanine base in one strand hydrogen bonds with a thymine base in the opposite strand An adenine base in one strand hydrogen bonds with a thymine base in another strand or the guanine base in one strand hydrogen binds with a cytosine base in another strand This AT/GC rule of specificity, explained the earlier data of Chargaff showing tha the DNA from many organisms contains equal amounts of adenine and thymine The dna from many organisms contains equal amounts of adenine and thymine and equal amounts of guanine and cytosine The AT/GC rule indicates that purines (the nitrogenous bases with the two ring structure, adenine and guanine) will always hydrogen bond with pyrimidines (the nitrogenous bases with a single ring structure, thymine and cytosine- an in rna, uracil replacing thymine and hydrogen bonding with adenine) This keeps the width of the double helix relatively constant THREE HYDROGEN BONDS OCCUR BW GUANINE AND CYTOSINE 3 HYDROGEN BONDS OCCUR BW GUANINE AND CYTOSINE 3 hydrogen bonds occur bw guanine and cytosine 2 hydrogen bonds occur bw adenine and thymine For this reason, dna sequences that contain a higher proportion tend to form a more stable double stranded helix For this reason, dna sequences that contain a higher proportion of guanine and cytosine tend to form a more stable double stranded structure, because 3 hydrgoen bonds form bw a guanine and cytosine nitrogenous base located on two antiparallel strands, and this multitude of 3 hydrogen bond bonds and attachments bw guanine and cytosine nitrogenous bases due to the higher concentration of guanine and cytosine will result in a more stable double helix in a more stable dna structure The AT/GC rule implies that we can predict the sequence on one dna strand if the sequence in the opposite strand of dna is known If we are considering a dna strand with the sequence of 5'-ATGGCGGATTT-3' if we are considering this dna strand, the opposite strand would have to be antiparallel to the original strand, with a corresponding nucleotide sequence in particular, a corresponding sequence of nitrogenous bases to complement the original strand, going from 3 prime to 5 prime, 3'-TACCGCCTAAA-5' In genetic terms, we would say that these two sequences these two sequences of dna, these particular two sequences of nitrogenous bases within these two strands of dna are complementary to one another We could also say that these two dna sequences that are complementary to one another, we could say that these two dna sequences, these two dna strands exhibit complementarity In addition, we may have notice that the sequences of dna, that the sequences of dna the two strands are labeled with 5 prime and 3 prime ends The two stands are labeled with 5 prime and 3 prime ends These numbers designated the direction of the dna backbones, of the direction of the backbones of these strands, the 5 prime and 3 prime designation The direction of dna strands is depicted within this book with the particular dna strands that it is showing When going from the top of this figure to the bottom, there is one strand running in the 5 prime to 3 prime direction, and the other strand is running in the 3 prime to the 5 prime direction The opposite orientation of these two intertwining dna strands, the opposite orientation of these two intertwining dna strands where, when read from top to bottom, one is going in the 5 prime to 3 prime direction and the other is going in the 3 prime to 5 prime direction, is designated as an antiparallel arrangement An antiparallel arrangement of the two strands of the double helix of dna was a model, an arrangement initially proposed in the models created by Watson and crick There is a schematic model withinthe book that emphasizes particular molecular features of the structure of DNA The bases within this model of the structure of DNA are depicted as flat and rectangular structures, and these flat and rectangular structures hydrogen bond with one another in pairs, adenine binding to thymine and guanine binding to cytosine The hydrogen bonds are the dotted links bc the dna bases depicted as flat and rectangular structures Although the dna bases are not actually rectangular they do indeed form flattened planar structures Within dna the bases are oriented so that the flattened regions are facing one another The bases are oriented so that the flattened regions are facing one another, and this arrangement is referred to as base stacking If you think of the bases as flat plates, these plates are stacked on top of one another in the double stranded dna structure, as depicted within the model Along with hydrogen bonding, base stacking, the bases shaped like rectangles that are oriented so that the flattened regions are facing one another, is a structural feature that stabilizes the double helix structure of the dna by excluding water moleucles The helical structure of the dna backbone depends on the hydrogen bonding occurring bw base pairs and also on base stacking, the orientation of the bases so that the flattened regions are facing eachother The direction of the dna double helix, the double helix spirals in a direction that is called right handed The dna double helix spirals in a direction designated as right handed As the dna double helix spirals away from you if one end of the helix is located close to you, and the other end of the helix is at the opposite end of the desk, as the dna double helix spirals away from you, a right handed helix, a right handed double helix in that particular conformation, a right handed conformation, turns in a clockwise direction Both strands in the dna double helix shown spiral in a right handed conformation, in a clockwise direction There is also a space filling model of dna within the textbook There is also a space filling model, and within this space filling model, the atoms of this space filling model are represented by spheres This model this space filling model emphasizes the surface features of dna It emphasizes the surface features of dna The backbone of the dna double helix that is composed of pentose sugars and phosphate groups is on the outermost surface Within a living cell, the backbone composed of pentose sugars and phosphate groups, within a living cell has the most contact with water In contrast, the bases are more internally located within the double helix, within the double stranded structure Biochemists utilize the term grooves in order to designate and describe the indentations where the atoms of bases are in contact with the surrounding water Biochemists utilize the term grooves in order to designate and describe the indentations where the atoms of bases are in contact with the surrounding water Biochemists utilize the term grooves in order to describe and designate the indentations within the double helix structure where the atoms of the bases are in contact with the surrounding water As you travel around the dna helix the structure of dna has two groove the major groove and the minor groove As you travel around the dna helix the structure of dna has two grooves the major groove and the minor groove, grooves are indentations within the double helix structure where the atoms of the base pairs face and come into contact with the surrounding water Proteins are able to bind to dna and affect the conformation of the dna and its function Some proteins are able to hydrogen bond to the bases found within the major groove, the groove where these are indentations where the atoms of the base pairs within this indentation within this area are in contact with the surrounding water, proteins may be able to hydrogen bond to these major larger groooves This hydrogen bonding can be extremely precise, and that can result in a particular protein interacting with a v particular sequence of bases A protein is therefore able to recognize a specific gene and affect its ability to be transcribed, affect this gene's ability to be transcribed Alternatively, other proteins bind to the dna backbone, other proteins bind to the backbone of the dna There are histone proteins that form ionic interactions with the negatively charged phosphates the negatively charged phosphate groups of the dna backbone, and these histones are extremely important and play an important role in regards to the compaction of dna within eukaryotic cells Histones also play an important role in regards to the transcription of genes

repeating nucleotide structure

There is a repeating unit of nucleotides that composes a single strand of RNA and DNA The locations of the attachment sites of the base and phosphate to the sugar molecule are important to the function of the nucleotide The locations of the attachment sites of the base and phosphate to the sugar molecule are important to the function of the nucleotide The locations of the attachment sties of the base and the phosphate group to the sugar molecule, to either the deoxyribose or ribose are important to function of the nucleotide The location of the attachment sites of the nitrogenous base and phosphate group to the sugar within the structure of a nucleotide, these locations of the attaachemnt sites of the nitrogenous base and the phosphate group or groups to the sugar is important in regards to the function of the nucleotide In the sugar ring, in the ring of the sugar composing the nucleotide, either the deoxyribose sugar or the ribose sugar, the carbon atoms are numbered in a clockwise direction In the sugar ring, in the ring of the pentose sugar composing a given nucleotide, the carbon atoms are numbered in a clockwise direction In the sugar ring, in the ring of the pentose sugar composing a given nucleotide, the carbon atoms are numbered in a clockwise direction, beginning with a carbon atom that is adjacent to the ring oxygen atom The clockwise direction of the labeling of the carbon atoms composing the given pentose sugar begins with a carbon labeled with 1' (1 prime) that is adjacent to the oxygen molecule within this pentose sugar, located at the top point of the pentagon structure The 5th carbon is always located outside of the ring structure of the pentose sugar, on both the deoxyribose sugar and the ribose sugar The 5th carbon is always located outside of the established and visible discernible ring structure of the pentose sugar The 5th carbon is always located outside of the established and visible discernible ring structure of the pentose sugar In a single nucleotide, in a single given nucleotide, the nitrogenous base is always attached to the 1 prime carbon atom of the sugar, it is always attachedto the 1 prime carbon atom of the sugar, the 1 prime carbon atom that is adjacent to the oxygen atom located at the point of the pentagon composing the sugar The nitrogenous base within a nucleotide composition, the nitrogenous base composing a nucleotide will always be attached to the 1 PRIME carbon, the first carbon of the pentose sugar, recall that the first carbon of the pentose sugar is located adjacent to the oxygen atom of the pentose sugar, this oxygen atom is located at the pinnacle of the pentagon structure of the pentose sugar, and this 1 prime carbon is located adjacent to this oxygen atom, to the right of the oxygen atom, and this, the 1 prime carbon, is where the nitrogenous base attaches One or more phosphate groups are attached to the 5 prime carbon The 5 prime carbon is not included within the ring structure of the pentose sugar, it is outside of the ring structure of the pentose sugar, it is located outside of thi, and the 5 prime carbon of the pentose structure is where the phosphate group or phosphate groups attach The OH group that is attached to the 3 prime carbon of the pentose sugar The OH group that is attached to the 3 prime carbon of the pentose sugar The OH group that is attached to the 3 prime carbon of the pentose sugar The OH group that is attached to the 3 prime carbon of the pentose sugar, this OH group is important in regards to allowing nucleotides to form covalent linkages with one another The OH group attached to the 3 prime carbon of the pentose sugar is important in regards to nucleotides in a repeating structure being able to form covalent linkages with one another The terminology utilized in order to describe the nucleid acid units is based on three structural features, the type of base the type of nitrogenous base attached to the first prime, the 1 prime carbon of the pentose sugar, the type of sugar whether it is a deoxyribose or ribose sugar, and the number of phosphate groups attached to the 5 prime carbon of this pentose sugar The terminology utilized in order to identify and designate nucleic acid units is based upon three criteria, three structural features: The type of base- the type of base that is attached to the 1 prime carbon, the 1 prime carbon, the first carbon of the pentose sugar The type of sugar the type of pentose sugar, whether it is a deoxyribose sugar or a ribose sugar The number of phosphate groups attached to the 5 prime carbon of the pentose sugar, the number of phosphate groups attached to the 5 prime carbon of the pentose sugar WHEN A NITROGENOUS BASE IS ATTACHED ONLY TO A SUGAR and there is no phosphate group attached to the 5 prime carbon of the pentose sugar When a nitrogenous base is attached only to a sugar, and there are no phosphate groups attached to the 5 prime carbon of the pentose sugar, this structure of a nitrogenous base attached to a pentose sugar is known and designated as a nucleoside If there is an adenine nitrogenous base (adenine is a purine with a double ring structure, recall that purines are the nitrogenous bases with the double ring structure, and the two purine nitrogenous bases are adenine and guanine) If there is an adenine nitrogenous base attached to a ribose sugar, this pair of the adenine nitrogenous base and a ribose sugar adenosine Nucleosides that contain guanine thymine cytosine or uracil are called: Guanosine Thymidine Cytidine Uridine The nucleosides are: Adenosine- an adenine nitrogenous base plus a ribose sugar Guanosine- a guanine nitrogenous base plus a ribose sugar Thymidine- a thymine nitrogenous base plus a ribose sugar Cytidine- a cytosine nitrogenous base plus a ribose sugar Uridine- a uracil nitrogenous base plus a ribose sugar When a base is attached to only a pentose sugar When a nitrogenous base is attached to only a pentose sugar, this is known as a nucleoside the nucleosides are designated as the following: Adenosine Guanosine Thymidine Cytidine Uridine These are the nucleoside the nitrogenous bases attached solely to a pentose sugar, with no phosphate groups attached to the 5 prime carbon of the pnetome sugar When only the bases are attached to deoxyribose, when the nitrogenous bases are simply attached to a deoxyribose pentose sugar and there are no phosphate groups attached to this deoxyribose sugar, they are called the following: deoxyadenosine Deoxyguanosine Deoxythymidine Deoxycytidine So the terminoly for nucleosides but due to the nitrogenous bases being attached to a deoxyribose pentose sugar with no phosphate groups attached to the 5 prime carbon, there is a deoxy prefix The covalent attachment of one or more phosphate molecules to a nucleoside creates a nucleotide The covalent attachment of one or more phosphate moelcules to the 5 prime carbon of the pentose sugar turns the structure into a nucleotide, the structure due to the attachment of one or more phosphate molecules to the 5 prime carbon of the pentose sugar within the structure is now designated as a nucleotide, consisting of a nitrogenous base attached to the 1 prime carbon of the pentose sugar either deoxyribose or ribose, and 1 or more phosphate groups, one or moe phosphate molecules attached to the 5 prime carbon of the pentose sugar, either deoxyribose or ribose If a nucleotide contains the nitrogenous base adenine, ribose, and phosphate: Due to the combination of the nitrogenous base adenine and a ribose sugar rather than a deoxyribose sugar, due to the combination of the nitrogenous base adenine and a ribose sugar, the designation adenosine comes in Due to the single phosphate group attached to the 5 prime carbon of the pentose sugar, the word monophosphate to designate one phosphate is added Therefore a structure containing a nitrogenous base, adenine, attached to a ribose sugar attached to a single phosphate group, this structure is designated as adenosine monophosphate., this is abbreviated as adenosine monophosphate If a structure, a nucleotide contains adenine, ribose, and three phosphates, three phosphate groups/molecules attached to the 5 prime carbon of the ribose sugar, the structure, the nucleotide is designated as adenosine triphosphate, or ATP If there is a nucleotide, a structure containing the nitrogenous base guanine, a ribose sugar, and three phosphate groups attached to the 5 prime carbon of this ribose sugar, this nucleotide will be designated as guanosine triphosphate, or GTP A nucleotide can also be composed of the nitrogenous base adenine, the sugar deoxyribose, and three phosphate groups attached to the 5 prime carbon of the deoxyribose sugar A nucleotide can be composed of the aforementioned components of the nitrogenous base adenine, the pentose sugar deoxyribose, and 3 phosphate groups attached to the 5 prime carbon fo the pentose sugar deoxyribose This nucleotide will be designated as deoxyadenosine triphosphate This nucleotide composed of the nitrogenous base adenosine, the pentose sugar deoxyribose, and 3 phosphate groups attached to the 5 prime carbon of the deoxyribose pentose sugar is designated as deoxyadenosine trisphosphate, dATP

viral genomes

VIRAL GENOMES ARE PACKAGED INTO THE CAPSID THROUGH THE IMPLEMENTATION OF AN ASSEMBLY PROCESS when there is an infected cell, the reproductive cycle of the virus eventually leads to the synthesis of VIRAL NUCLEIC ACIDS AND PROTEINS the reproductive cycle of the virus when there is a cell that has been infected by a virus, this reproductive cycle of the virus will eventually lead to the creation of VIRAL NUCLEIC ACIDS AND PROTEINS these newly synthesized viral chromosomes and capsid proteins that are created due to the reproductive cycle of the virus, these newly created viral chromosomes and capsid proteins will then conglomerate and assemble to make MATURE VIRUS PARTICLES they will conglomerate these viral chromosomes and capsid proteins will then conglomerate and assemble into MATURE VIRUS PARTICLES viruses that have a simple structure are able to SELF ASSEMBLE viruses with a simple structure may self assemble SELF ASSEMBLY OF VIRUSES WITH A SIMPLE STRUCTURE INVOLVES THE NUCLEIC ACID AND CAPSID PROTEINS SPONTANEOUSLY BINDING TO ONE ANOTHER IN ORDER TO FORM A MATURE VIRUS the self assembly of viruses with a simple structure occurs through the following mechanism it involves the nucleic acid and the capsid proteins spontaneously binding to one another in order to form a mature and put together virus the nucleic acid and the capsid proteins spontaneously bind to one another in order to form A MATURE AND PUT TOGETHER VIRUS this process usually occurs with virus composed of a simple structure, where the nucleic acid and capsid proteins spontaneously bind to one another and form a mature virus WHAT IS ONE KIND OF SELF ASSEMBLING VIRUS one kind of self assembling virus is the TOBACCO MOSAIC VIRUS the tobacco mosaic virus is a self assembling virus, a virus who's structure is fairly simplistic, to the extent that it is able to self assemble, and its nucleic acid and capsid proteins spontaneously bind to one another in order to form a mature virus in the tobacco mosaic virus, the proteins assemble around the RNA genome THE RNA GENOME BECOMES TRAPPED INSIDE THE HOLLOW CAPSID the proteins assemble around the RNA genome the RNA genome becomes trapped inside the hollow capsid this assembly process of the proteins assembling around the RNA genome of the tobacco mosaic virus and the RNA genome can occur in vitro if the PURIFIED CAPSID PROTEINS AND RNA ARE MIXED TOGETHER the assembly process of the proteins assembling around the RNA genome of the tobacco mosaic virus and the RNA genome can occur in vitro depending on whether the PURIFIED CAPSID PROTEINS AND THE RNA ARE MIXED TOGETHER this can means the the proteins assemble around the RNA genome, and the RNA genome becomes trapped inside of the hollow capsid, the entire process taking place in vitro due to the purified capsid proteins and the RNA being mixed together in contrast, some viruses such as THE T2 BACTERIOPHAGE HAVE MORE COMPLICATE STRUCTURES these more complicated structures of the T2 bacteriophage DO NOT SELF ASSEMBLE these more complicated structures of the T2 BACTERIOPHAGE ARE NOT CAPABLE OF SELF ASSEMBLY (recall that viruses with simple structures are v capable of self assembly, and the self assembly occurs when the proteins assemble and conglomerate around the RNA genome, and the RNA genome that the proteins assemble and conglomerate around becomes trapped inside of the hollow capsid, such as with the tobacco mosaic virus, this above example is one of how the tobacco mosaic virus self assembles) the T2 BACTERIOPHAGE has a more complicated structures, and therefore is not capable of self assembly the correct assembly of this more complex virus that is not capable of self assembly due to the complexity of its structure is the following: the correct assembly of this more complex virus requires the assistance of proteins THAT ARE NOT FOUND WITHIN THE MATURE VIRUS PARTICLE ITSELF the correct assembly of this more complex virus requires the assistance of proteins that are not found within the mature complex virus particle itself the virus assembly of a complex virus requires the participation of noncapsid proteins, proteins that are not contained within the mature virus particle itself, the participation of these noncapsid proteins (that are not found within the mature virus particle itself) when the assembly of a complex virus requires the participation of capsid proteins, proteins that are not found within the mature virus particles, the process is KNOWN AS DIRECTED ASSEMBLY why is the process known as directed assembly? the process by which noncapsid proteins found outside of the virus particle are utilized in order to construct and assemble a virus is known as directed assembly why is it known as directed assembly? it is known as directed assembly because THE NONCAPSID PROTEINS proteins outside of the virus particles that are recruited to assist w protein assembly direct the PROPER ASSEMBLY OF THE VIRUS these recruited noncapsid proteins outside of the virus particles are recruited to assist and direct the proper assembly of the virus, and that is why this process of assembly is known as directed assembly what are the functions of the noncapsid proteins that are responsible for the directed assembly of the virus? there are some noncapsid proteins known as SCAFFOLDING PROTEINS these scaffolding proteins catalyze the assembly process THESE SCAFFOLDING PROTEINS CATALYZE THE ASSEMBLY PROCESS the scaffolding proteins catalyze the assembly process these scaffolding proteins are transiently associated with the capsid in addition to catalyzing the assembly process of the complex virus (recall that these are noncapsid proteins that are recruited in order to assemble the virus, and also recall that they are transiently associated with the capsid, in addition to catalyzing this assembly process as noncapsid proteins recruited by the cell in order to do so) however, as the viral assembly nears completion, as the virus is almost completely put together and completed, the scaffolding proteins are taken out of the mature virus as these noncapsid proteins are no longer needed in order to assemble the now mature and assembled and conglomerated virus other noncapsid proteins act as proteases- THESE PROTEASES SPECIFICALLY CLEAVE VIRAL CAPSID PROTEINS there are other noncapsid proteins that are recruited to assemble the virus, and some of these noncapsid proteins are dedicated as PROTEASES PROTEASES ARE RESPONSIBLE FOR SPECIFICALLY CLEAVING VIRAL CAPSID PROTEINS the cleavage of these specific viral capsid proteins that is carried out and implemented by proteases recruited as noncapsid proteins by the virus in order to implement assembly causes something to occur the cleavage of these viral capsid proteins by the proteases leads to a SMALLER CAPSID PROTEIN THAT IS SOMEWHAT SMALLER AND ABLE TO ASSEMBLE CORRECTLY the cleavage of these viral capsid proteins by the proteases that are recruited by the virus as noncapsid proteins results in another capsid protein that is smaller and able to assemble properly and correctly FOR A LOT OF VIRUSES< THE CLEAVAGE OF CAPSID PROTEINS INTO SMALLER UNITS IS AN IMPORTANT EVENT THAT PRECEDES VIRAL ASSEMBLY the cleavage of capsid proteins into smaller units is an important event that needs to occur before viral assembly occurs recalling the structure of the tobacco mosaic virus the tobacco mosaic virus is a simple virus and thus self assembling the self assembling virus is composed of a coiled RNA molecule this coiled RNA molecule is surrounded by 2130 IDENTICAL PROTEIN SUBUNITS the coiled RNA molecule is surrounded by 2130 IDENTICAL PROTEIN SUBUNITS the diagram that is depicted is one of only a portion of the tobacco mosaic virus there are several layers of proteins surrounded the RNA genome that have been omitted in order to showcase how the 2130 identical protein subunits surround the RNA genome the RNA genome is trapped inside of the protein coat the tobacco mosaic virus is a simple virus contained by 2130 identical protein subunits, and it, as a simple virus, is capable of self assembly

viruses

VIRUSES ARE SMALL INFECTIOUS PARTICLES viruses are small infectious particles, they are small particles that are also infectious these small infectious particles contain NUCLEIC ACID AS THEIR GENETIC MATERIAL the genetic material of viruses is nucleic acid recall that viruses are small, infectious particles whose genetic material is composed of nucleic acids viruses, these small infectious cells are surrounded by A PROTEIN COAT A CAPSID what are bacteriophages specifically? bacteriophages fall under the category of viruses BACTERIOPHAGES ARE VIRUSES THAT INFECT BACTERIA SPECIFICALLY bacteriophages are viruses the infect bacteria, bacterial cells specifically THE CAPSID OF BACTERIOPHAGES, the protein coat that surrounds bacteriophages, a type of virus that infects bacterial cells may contain A SHEATH A BASE PLATE TAIL FIBERS the capsid, the protein coat of bacteriophages may contain: A SHEATH A BASE PLATE TAIL FIBERS there are also particular eukaryotic viruses (recall that viruses are small infectious particles that infect cells) these particular eukaryotic viruses have an envelope consisting of a MEMBRANE EMBEDDED W SPIKE PROTEINS these particular eukaryotic viruses have an envelope consisting of A MEMBRANE EMBEDDED WITH SPIKE PROTEINS this membrane consisting of spike proteins is covering these particular eukaryotic viruses BY THEMSELVES VIRUSES ARE NOT CONSIDERED CELLULAR ORGANISMS by themselves, viruses are not considered cellular organisms THEY ARE NOT CONSIDERED CELLULAR ORGANISMS BY THEMSELVES why are viruses by themselves not considered cellular organisms? they are not considered cellular organisms bc they do not contain ENERGY PRODUCING ENZYMES RIBOSOMES OR CELLULAR organelles they are not considered cellular organisms bc they do not contain energy producing enzymes, ribosomes or cellular organelles, all components that result in the designation of something as a cellular organism due to viruses not having energy producing enzymes, ribosomes, or cellular organelles, they are not considered cellular organisms VIRUSES THEREFORE RELY ON THEIR HOST CELLS their host cells are the cells that the viruses infect THE HOST CELLS ARE THE CELLS THAT THE VIRUSES INFECT THE HOST CELLS ARE THE CELLS THAT THE VIRUSES INFECT these viruses rely on their host cells, the cells that these viruses infect in order to make new viruses, in order for these viruses to proliferate they rely on their host cells in order to proliferate, they rely on the cells they infect in order to synthesize new viruses THE MAJORITY OF VIRUSES EXHIBIT A LIMITED HOST RANGE what is a limited host range? a limited host range is THE SPECTRUM OF HOST SPECIES (and incidentally, all the cells within those particular species) that the virus can infect the host range of a virus is the spectrum of host species/host cells that this virus is able to infect and utilize and designate as a host cell MANY VIRUSES CAN INFECT ONLY SPECIFIC TYPES OF CELLS OF ONE HOST SPECIES many viruses are only able to infect particular types of cells of a particular host species so they can infect cells within this host species but only particular types of cells within this host species depending on the life cycle of the virus THE HOST CELL MAY OR MAY NOT BE DESTROYED DURING THE PROCESS OF VIRAL REPLICATION AND RELEASE depending on the life cycle of the virus, how long the virus is able to sustain itself, the host cell may or may not be destroyed during the implemented processes of viral replication and viral release

human karyotype

WHAT IS A HUMAN KARYOTYPE? a human karyotype is a display that showcases the entire complement of chromosomes within the somatic cells of a human individual how is a human karyotype made? a human karyotype is made through a process described in Ch. 3 WHAT IS A KARYOTYPE a karyotype is a MICROGRAPH a karyotype is a micrograph in which ALL OF THE CHROMOSOMES WITHIN A SINGLE CELL (USUALLY A SINGLE SOMATIC CELL) HAVE BEEN ARRANGED IN A STANDARD FASHION, ORGANIZED IN SOME MANNER all of the chromosomes within the nucleus of a single cell have been organized and showcased in a particular, specified, distinguishing manner when karyotypes are prepared, when a full micrograph showcasing all of the chromosomes within the nucleus of a somatic cell of an organism are organized, they are all aligned in a particular manner: the short, p arms on top, and the long, q arms on the bottom all of the chromosomes within a karyotype are organized with the p arms, the short arms, on the top, and the q arms, the long arms, on the bottom by convention, the chromosomes are numbered roughly, organized and distinguished according to their size THE LARGEST CHROMOSOMES are given the smallest numbers the SMALLEST CHROMOSOMES are given the largest number by convention, the chromosomes are organized and distinguished according to their size an example showcasing the common utilization of this convention, within humans, the largest chromosomes are designated as 1, 2, and 3 chromosomes with the designations of 1, 2, and 3 are relatively large in size chromosomes with the designation of 21 and 22 are the smallest chromosomes in the somatic cells of humans an exception to this conventional numbering system, where chromosomes are organized, distinguished, and designated a number according to size is not obeyed by the designation of the sex chromosomes the sex chromosomes are designated with letters different chromosomes oftentimes have SIMILAR SIZES AND CENTROMERIC LOCATIONS, geneticists need to utilize additional methods besides chromosome size and centromeric location in order to accurately distinguish bw chromosomes an example of similarity in regards to chromosome size and centromeric location that can make it hard to distinguish chromosomes from one another: chromosomes 8, 9, and 10 all have a similar size, and similar locations for their centromere therefore going off of size and centromeric location alone is not enough to adequately and confidently distinguish these chromosomes from one another cytogeneticists and geneticists overall therefore need to utilize additional methods in order to confidently and verifiably distinguish the chromosomes within a karyotype they are creating therefore for more detailed and verifiable chromosomal identification, chromosomes are TREATED WITH STAINS chromosomes are treated with stains in order to produce CHARACTERISTIC AND DISTINCT BANDING PATTERNS chromosomes are treated with stains in order to produce CHARACTERISTIC AND DISTINCT BANDING PATTERNS that will assist cytogeneticists and geneticists in verifiably and confidently distinguishing chromosomes through the utilization of this additional chromosomal distinction method there are several different staining procedures that are utilized by cytogeneticists in order to distinguish chromosomes from one another verifiably when they are creating a karyotype one type of staining that cytogeneticists utilize in order to further distinguish chromosomes is G BANDING G BANDING this procedure involves CHROMOSOMES BEING TREATED WITH MILD HEAT OR WITH PROTEOLYTIC ENZYMES chromosomes are treated with mild heat or chromosomes are treated with proteolytic enzymes proteolytic enzymes are enzymes that are able to partially digest chromosomal proteins PROTEOLYTIC ENZYMES ARE ENZYMES THAT ARE RESPONSIBLE FOR PARTIALLY DIGESTING CHROMOSOMAL PROTEINS proteolytic enzymes are able to and will partially digest chromosomal proteins in G banding, which is one of the standardized procedures utilized in order to stain chromosomes so that they showcase CHARACTERISTIC BANDING PATTERNS AND therefore verifiable distinction of these chromosomes can occur, chromosomes are treated to mild heat or proteolytic enzymes (proteolytic enzymes are able to and will partially digest chromosomal proteins) WHEN CHROMOSOMES ARE EXPOSED TO THE DYE CALLED GIEMSA GIEMSA this is a dye named after its inventor GUSTAV GIEMSA giemsa- this is a dye named after its inventor, Gustav Giemsa when chromosomes are stained with Giemsa, when chromosomes are exposed to the dye Giemsa, THERE ARE SOME CHROMOSOMAL REGIONS THAT BIND THE GIEMSA DYE HEAVILY these chromosomal regions that bind the giemsa dye heavily PRODUCE A DARK BAND so when chromosomes are stained with Giemsa, there are particular chromosomal regions that bind this dye heavily, and therefore, due to binding this Giemsa dye heavily, produce a dark and discernible band, a dark, heavy, discernible band that can be seen microscopically by a cytogeneticist in other regions of the chromosome, regions of the chromosome where the Giemsa dye does not bind, THE STAIN DOES NOT BIND AT ALL, OR HARDLY BINDS AT ALL and therefore a light band is produced in regions of the chromosomes that do not bind the Giemsa dye, the dye does not bind at all, or binds v little, and a light band is produced therefore on the chromosomes, there will be regions that have heavily bound to the dye and produce, heavy, dark, discernible bands, and regions that are not heavily bound to the dye, that are lightly bound to the dye and therefore produce light, yet still discernible bands THE MECHANISM OF STAINING IS NOT FULLY UNDERSTOOD OR COMPREHENDED however, the dark bands are thought to represent regions of chromosomes that are more tightly compacted it is thought that more tightly compacted and condensed regions of chromosomes will bind the dye more heavily and produce a dark, heavy, discernible band that designates these regions of chromosomes as tightly compacted regions THE ALTERNATING PATTERN OF G BANDS is a unique feature for each chromosome, this is how chromosomes are distinguished from one another verifiably, in addition to the usage of chromosome size and centromeric location, through standardized staining procedures, such as the commonly used procedure with Giemsa, where the G banding patterns that the chromosomes develop and showcase due to being stained with dye (where some regions, most likely more tightly compacted regions of chromosomes, bind the dye heavily and produce a dark, heavy, discernible, distinguishable band, and other regions of the chromosomes do not bind the dye heavily and produce a light yet still discernible band) are utilized in order to verifiably distinguish chromosomes as unique from one another in the case of specifically human chromosomes, chromosomes found within the nuclei of human cells APPROXIMATELY 300 G BANDS CAN USUALLY BE DISTINGUISHED DURING METAPHASE when chromosomes are in metaphase (which is when they are the most tightly compacted and condensed, with a diameter of 1400 nm), APPROXIMATELY 300 G BANDS Can BE DISTINGUISHED ON THESE CHROMOSOMES due to the higher level of compaction of these chromosomes during metaphase A LARGER NUMBER OF G BANDS IN THE RANGE OF 800 G BANDS CAN BE OBSERVED MICROSCOPICALLY IN PROMETAPHASE CHROMOSOMES a larger number of g bands, somewhere in the range of 800 g bands can be observed microscopically in prometaphase chromosomes why can more g bands be observed microscopically in pro metaphase chromosomes? why can more g bands be observed microscopically, somewhere in the range of 800 in pro metaphase chromosomes (as compared to the more tightly compacted metaphase chromosomes, where about 300 g bands can be observed) more g bands can be observed in pro metaphase chromosomes bc PROMETAPHASE CHROMOSOMES ARE SLIGHTLY MORE EXTENDED THAN METAPHASE CHROMOSOMES bc pro metaphase chromosomes are slightly more extended than metaphase chromosomes (which are more tightly compacted and therefore less extended), more G bands can be observed on pro metaphase chromosomes what is the conventional numbering system that is utilized in order to distinguish and designated G bands along a set, a pair of human chromosomes? what is the conventional numbering system of G bands? the LEFT CHROMATID IN EACH PAIR OF SISTER CHROMATIDS looking at the left sister chromatid in each pair of sister chromatids constituting a chromosome, the left sister chromatids shows the EXPECTED BANDING PATTERN of the chromosome that will occur during metaphase the right sister chromatid in the sister chromatid pair that constitutes a chromosome showcases the banding pattern that is expected to show up during pro metaphase WHY IS THE BANDING OF EUKARYOTIC CHROMOSOMES USEFUL? why is the banding of eukaryotic chromosomes useful? the banding of eukaryotic chromosomes is useful because when chromosomes are stained, chromosomes can be distinguished from one another due to the unique and discernible banding patterns that they each individually showcases to give themselves a unique and verifiable identifier chromosomes can be distinguished from one another due to staining even if they are of similar size and have similar centromeric locations staining offers an additional method by which similar chromosomes (chromosomes similar in regards to size and centromeric location the first two characteristics used to distinguish chromosomes) can be officially and verifiably distinguished from one another, as different chromosomes will always show distinct and identifiable banding patterns when stained, allowing cytogeneticists and geneticists to distinguish otherwise v similar chromosomes (in regards to size and centromeric location) from one another banding patterns are ALSO UTILIZED IN ORDER TO DETECT CHANGES IN CHROMOSOME STRUCTURE banding patterns are also utilized in order to detect changes within chromosomal structure CHROMOSOMAL REARRANGMENTS (inversions, translocations, etc) and CHANGES TO THE OVERALL AMOUNT OF GENETIC MATERIAL WITHIN THE NUCLEUS OF A CELL CHANGES TO THE OVERALL AMOUNT OF GENETIC MATERIAL, THE TOTAL NUMBER OF CHROMOSOMES, AS WELL AS CHANGES IN CHROMOSOMAL STRUCTURE, GENETIC SEQUENCES (such as inversions, translocations, duplications, deletions) CAN BE BETTER DETECTED WITHIN CHROMOSOMES WITH BANDING PATTERNS THEY ARE EASILY DETECTED WITHIN CHROMOSOMES WITH BANDING PATTERNS that can be compared to the established normal banding pattern of that chromosome to see any genetic variation CHROMOSOMAL BANDING CAN ALSO BE UTILIZED IN ORDER TO ASSESS THE EVOLUTIONARY RELATIONSHIPS BW SPECIES chromosomal banding can finally also be utilized in order to assess and evaluate the evolutionary relationships bw species the evolutionary relationship bw species can be assessed and evaluated through chromosomal banding RESEARCH STUDIES that have been previously implemented have shown THAT THE SIMILARITY OF CHROMOSOMAL BANDING PATTERNS IS A PLAUSIBLE AND VERIFIABLE INDICATOR OF GENETIC RELATEDNESS chromosomal banding patterns are a verifiable indicator of genetic relatedness bw species genetic relatedness bw species can be established due to chromosomal banding

comparative genomic hybridization

WHAT IS COMPARATIVE GENOMIC HYBRIDIZATION comparative genomic hybridization is utilized in order to detect chromosome deletions and duplications comparative genomic hybridization is utilized in order to detect chromosome deletions and duplications the process of comparative genomic hybridization is utilized in order to detect chromosomal duplications and deletions the process of comparative genomic hybridization is utilized in order to detect chromosomal duplications and deletions CHROMOSOMAL DUPLICATIONS AND DUPLICATIONS MAY INFLUENCE THE PHENOTYPES OF INDIVIDUALS WHO INHERIT THEM chromosomal duplications and deletions may influence impact and affect the phenotypes (the morphological, physiological, and behavioral characteristics) of the individuals that inherit these chromosomal duplications and deletions we understand that chromosomal duplications and deletions can affect and alter the phenotypes of the individuals that inherit these chromosomal duplications and deletions WHY ARE RESEARCHERS V INTERESTED IN THESE TYPES OF CHROMOSOMAL CHANGES researchers are v interested in these types of chromosomal changes bc of how these chromosomal changes, these chromosomal duplications and deletions may be related to cancer this topic is specifically discussed in chapter 22, but chromosomal aberrations, chromosomal deletions and duplications have been associated with many types of human cancers chromosomal aberrations, chromosomal deletions and duplications have been associated with many different types of human cancers though such changes, such as chromosomal deletions and duplications, these types of chromosomal aberrations may be detectable by traditional chromosomal staining and karyotyping methods these types of chromosomal aberrations, such as chromosomal duplications and deletions may be detectable through methods such as chromosomal staining and karyotyping, where colchicine is utilized in order to freeze cells during the time that they are undergoing the process of cellular division and in either the prophase or metaphase stage of mitosis, the cells are then lysed, the chromosomes, the genetic material taken out of the nucleus and stained with giemsa, then secured on a slide, with a computerized program taking snapshots of them in order to organize them into a karyotype, where they are arranged based on size and homology, size to number them, the smallest being designated with the highest numbers and the largest being designated with the lowest numbers, and them being paired due to size, centromeric locations, and banding patterns due to giemsa staining however, some small duplications and deletions may be extremely difficult to detect in this manner through the utilization of chromosomal staining and karyotyping however, researchers have been able to develop more advanced and successful methods of being able to detect these smaller and less easy to spot chromosomal aberrations, these smaller changes in chromosomal structure, more sensitive methods that are more likely to find fairly undetectable chromosomal aberrations and changes one of these methods is comparative genomic hybridization comparative genomic hybridization is one of the more sensitive methods utilized in order to identify smaller chromosomal aberrations, smaller and harder to detect chromosomal duplications and deletions that cannot be detected, pinpointed, and identified simply thought the usage of chromosomal staining and karyotyping processes that are generally successful at identifying larger chromosomal aberrations, larger chromosomal duplications and deletions in 1992, Anne Kallioniemi, Daniel Pinkel, and colleagues devised a method CALLED COMPARATIVE GENOMIC HYBRIDIZATION CGH this technique is largely and widely used in order to determined if cancer cells have changes in chromosome structure, such as chromosomal duplications or deletions this technique of comparative genomic hybridization is utilized widely in order to determine if cancer cells have changes in their chromosome structure, such as chromosomal duplications or deletions in order to begin this procedure of comparative genomic hybridization, which is a process largely used to identify if cancel cells have chromosomal aberrations such as duplications or deletions, DNA is isolated from a test sample in the case of its invention, DNA is isolated from a test sample, and in this case of the invention of the process of comparative genomic hybridization, the test sample that the DNA was isolated from was a sample of breast cancer cells DNA was also isolated from a sample of normal cells, a normal reference sample the DNa from the breast cancer cells, the DNA taken from the breast cancer cells was utilized as a template in order to make green fluorescent DNA the DNA from the breast cancer cells was utilized as a template in order to make green fluorescent DNA the DNA from the breast cancer cells, the DNA that was taken from the sample of breast cancer cells was utilized in order to make green fluorescent DNA the DNA taken from the sample of normal cells was utilized in order to make red fluorescent DNA the DNA taken from the sample of breast cancer cells was utilized in order to make green fluorescent DNA and the DNA taken from the normal sample of cells the DNA taken from the sample of normal cells was utilized in order to make red fluorescent DNA these green or red fluorescent DNA molecules average about 800 base pairs in length these green and red fluorescent molecules, these individually green and red DNA molecules that are made from the DNA collected from the sample of breast cancer cells and the reference sample of normal cells the DNA collected from the sample of the breast cancer cells and the reference sample of normal cells, probably normal somatic cells, cells of the body, are utilized in order to make green and red fluorescent DNA, which avg about 800 base pairs in length, and are made from sites that were scattered all along each chromosome they are made from sites scattered along each chromosome these green and fluorescent DNA molecules averaged 800 base pairs in length and were made from sites that were scattered all along each chromosome, these green and red fluorescent DNA molecules avg about 800 base pairs in length and were made from sites scattered all along the chromosomes the green and red DNA molecules were then denatured by heat treatment these green and red fluorescent DNA molecules that avgd about 800 base pairs in length and were created from sites all along the chromosomes underwent denaturation though the implementation of heat treatment the green and red fluorescent DNA molecules underwent denaturation due to the implementation of heat treatment equal amounts of two fluorescently labeled DNA samples were mixed together equal amounts of two fluorescently labeled DNA samples (Presumably one sample of the red fluorescently labeled DNA and one sample of the green fluorescently labeled DNA that were the same amount) were mixed together, and then this mixture of fluorescently labeled DNA (containing both red and green fluorescent DNA) was applied to normal metaphase chromosomes in which the DNA had also been denatured the sample of mixed green and red fluorescent DNA, the mixture containing two samples of equal amounts of fluorescently labeled DNA mixed together was applied to metaphase chromosomes, chromosomes in the phase metaphase the sample of mixed green and red fluorescent DNA, the mixture containing two samples of equal amounts of fluorscently labeled DNA was placed upon and applied to normal metaphase chromosomes, normal metaphase chromosomes in which the DNA had also been denatured, it was applied to metaphase chromosomes in which the DNA had also been denatured bc the fluorescently labeled DNA fragments and the metaphase chromosomes had both been denatured, the fluorescently labeled DNA strands found within the mixture containing equal amounts of fluorescently labeled DNA were able to bind to complementary regions on the metaphase chromosomes, the fluorescently labeled DNA strands were able to bind to complementary regions on the metaphase chromosomes, due to both the fluorescently labeled DNA strands and the metaphase chromosomes being denatured, due to both of them being denatured, the fluorescently labeled DNA strands were able to bind to complementary regions on the metaphase chromosomes THIS PROCESS IS DESIGNATED AS HYBRIDIZATION WHY IS THIS PROCESS DESIGNATED AS HYBRIDIZATION? this process is designated as hybridization (this process of fluorescently labeled DNA binding to complementary regions on the metaphase chromosomes) due to the fact that the DNA from one sample (one of the two samples of fluorescently labeled DNA in equal amounts that were mixed to form a mixture of equal amounts of two different types of fluorescently labeled DNA), a green or a red DNA strand, a red or a green fluorescently labeled DNA strand, forms a double stranded region with a DNA strand from another sample (a DNA strand from an unlabeled metaphase chromosome) following hybridization, when a DNA strand from one sample, a fluorescently labeled red or green DNA strand binds to complementary regions on metaphase chromosomes (in this particular case, as hybridization is simply defined as the DNA from one sample forming a double stranded region with a DNA from another sample, and in this specific case, what is occurring to constitute hybridization is the DNA from one sample- a red or green fluorescently labeled strand) forming a double stranded region by binding to complementary regions on metaphase chromosomes, which constitute the other sample of DNA) following the process of hybridization, the metaphase chromosomes were visualized through the utilization of a fluorescence microscopy following the process of hybridization, the metaphase chromosomes were visualized through the utilization of a fluorescence microscope the images were then analyzed by a computer, the images taken of the metaphase chromosomes observed through the utilization of a fluorescence microscope were then analyzed by a computer that was capable of analyzing the relative intensities of green and red fluorescence the images of the metaphase chromosomes observed by the fluorescence microscope were analyzed by a computer that could measure the intensity of red and green fluorescence WHAT ARE THE EXPECTED RESULTS OF THE COMPUTER ANALYSIS of the images taken of the metaphase chromosomes observed under a fluorescence microscope? what are the expected results of this analysis implemented on images of metaphase chromosomes viewed under a fluorescence microscope, an analysis implemented by a computer capable of measuring the intensity of green and red fluorescence? if a chromosomal region in the breast cancer cells and the normal cells are present in the same amount, the ratio bw green and red fluorescence should be 1 if a chromosomal region is deleted within the breast cancer cell line, then the ratio will be less than 1 if a chromosomal region is duplicated within the breast cancer cell line, the ratio will be greater than 1 what was the goal of this experiment? the goal of this experiment was for deletions or duplications chromosomal aberrations such as chromosomal deletions or duplications to be able to be detected by comparing the ability of fluorescently labeled DNA from cancer cells and fluorescently labeled DNA from normal cells to bind (hybridize) to normal metaphase chromosomes, the varying ability of fluorescently labeled DNA from cancer cells and the ability of fluorescently labeled DNA from normal cells to bind to metaphase chromosomes, to normal metaphase chromosomes the ratio of these differently fluorescently labeled chromosomes will be measured by a computer analyzing images of the hybridized structure of the fluorescently labeled DNA of cancer cells and human cells binding to complementary regions of the normal metaphase chromosomes, and calculating a ratio of the fluorescently labeled DNA from cancer cells to the fluorescently labeled DNA from normal cells, to see if there are any discrepancy if the ratio is 1, then there are probably no chromosomal aberrations, no chromosomal deletions or duplications in the chromosomes of the cancer cells if the ratio is greater than 1, then there are probably chromosomal deletions in the chromosomes of the cancer cells that are causing this ratio to be above 1 if the ratio is less than 1 there are probably chromosomal deletions within the chromosomes of the cancer cells that are causing this ratio to be less than 1 the interpretation of the data the data of figure 8.9-this shows a ratio of fluorescently labeled green DNA, the dna of the cancer cells, to the fluorescently labeled red DNA, the dna from the normal cells, from the reference sample, it shows this ratio of fluorescently labeled green cancer cell dna to fluorescently labeled red normal cell DNA along 5 different metaphase chromosomes looking at Chromosome 1, there is a large duplication, indicated by the ratio of 2 being greater than 1, indicating that there are chromosomal duplications in the chromosomes of the cancer cells one interpretation of this observation of a ratio of two bw the two different types of fluorescently labeled dna is that both copies of chromosome 1 within the cancer cells this dna was taken from contain chromosomal duplications in comparison to the ratio found in chromosome 1, chromosomes 9, 11, 16, and 16 have regions with a ratio value of 0.5 this value of the ratio bw green fluorescently labeled cancer DNA to red fluorescently labeled normal cell DNA indicates that one of the two chromosomes of these four types of chromosomes in the cancer cells carries a deletion, but the other chromosomes in the pairs of these 4 types of chromosomes do not contain deletions if there was a value for the ratio of 0, this would indicate that both copies of the chromosome within a pair contained deletions this technique of chromosomal hybridization, visualization of the hybridization under a fluorescence microscope, and computer analysis of the ratio of two types of fluorescent labeled dna, one from cancer cells, and one from normal cells can be utilized in order to map chromosomal duplications and deletions within cancer cells WHY IS THIS METHOD NAMED COMPARATIVE GENOMIC HYBRIDIZATION this method is named comparative genomic hybridization because a comparison is made bw the ability of the two DNA samples, the DNA taken from the cancer cells and the DNA taken from the normal cells, to hybridize to an entire genome the entire genome is in the form of metaphase chromosomes the fluorescently labeled DNAs can also be hybridized to a DNA microarray instead of metaphase chromosomes, they do not have to bind to metaphase chromosomes functioning as an entire genome this new method of two different types of fluorescently distinctly labeled dna binding to a DNA microarray is identified as array comparative genomic hybridization, a CGH, and it is gaining widespread utilization in the analysis of cancer cells

copy number variation (CNV)

WHAT IS THE TERM COPY NUMBER VARIATION? what does the term copy number variation designate, what does the term copy number variation designate? the term copy number variation REFERS TO A STRUCTURAL VARIATION copy number variation refers to A TYPE OF STRUCTURAL VARIATION copy number variation is a TYPE OF STRUCTURAL VARIATION copy number variation is A TYPE OF STRUCTURAL VARIATION copy number variation is A TYPE OF STRUCTURAL VARIATION copy number variation is a type of structural variation in regard to A SEGMENT OF DNA, a segment of DNA that is about 1000 base pairs or more than 1000 base pairs in length a segment of DNA that is 1000 base pairs or more in length EXHIBITS COPY NUMBER DIFFERENCES AMONGST MEMBERS OF THE SAME SPECIES copy number variation refers to a structural variation, a type of structural variation, where a dna segment that is 1000 base pairs or more in length varies in regards to its copy number amongst different members of the same species why does this occur, why is there copy number variation? why is there a difference in the number of copies of DNA segments that are a 1000 base pairs or more length within individuals of the same species? why do individuals of the same species have different numbers of copies of this segment of DNA that is 1000 base pairs or more in length, why is there this structural variation? there is the phenomenon of copy number variation, and there are multiple possibilities for why this phenomenon exists ONE POSSIBILITY IS THAT SOME MEMBERS OF A SPECIES MAY CARRY A CHROMOSOME WITH A GENE DELETION some members of a species may carry a chromosome with a gene deletion, with an entire gene or only part of a gene lost some members of a species may carry a chromosome that is missing a particular gene or a part of a gene so CNV can be due to particular members of the same species perhaps having a chromosome with a gene deletion, where they are now missing an entire gene or simply part of a gene another possibly for the phenomenon of copy number variation another reason for copy number variation is that THIS PHENOMENON MAY INVOLVE GENE DUPLICATION copy number variation may also be due to duplication an example of how duplication may result in copy number variation, differences in the number of copies of a particular DNA segment of 1000 base pairs or more amongst individuals of the same population: some members of a diploid species (meaning a species where developed individuals have 2 sets of chromosomes within all their cells, one set of chromosomes inherited maternally, and one set of chromosomes inherited paternally, one set of chromosomes inherited from each parent), some members of a diploid species MAY HAVE ONE COPY OF GENE A on both homologs of a chromosome, and thereby have two copies of the same gene so within some members of a species, they have ONE COPY OF GENE A on BOTH HOMOLOGS OF A CHROMOSOME, and therefore have two copies of the same gene, which is what they are probably supposed to have, one copy of the gene on each homologous chromosome of a pair, making for two copies of a gene, and a single allelic combination composed of two alleles, one allele contributed by one gene copy on one homologous chromosome however, other members of this species may have a single copy of gene A on one of its chromosomes that is part of a homologous pair, and on this chromosome's homologous chromosome of the pair, there are 2 copies of gene A, making for a total of 3 copies of gene A within this homologous pair of chromosomes, resulting in copy number variation THE HOMOLOG WITH TWO COPIES OF GENE A IS SAID TO HAVE UNDERGONE THE PROCESS OF SEGMENTAL DUPLICATION the homolog with two copies of gene A rather than just one is considered to have undergone segmental duplication, where a segment of this chromosome, the one containing the copy of gene A, was duplicated, in order to give this chromosome 2 copies of gene A COPY NUMBER VARIATION IS RELATIVELY COMMON IN ANIMAL AND PLANT SPECIES copy number variation within animal and plant species is relatively common occurs often copy number variation within animal and plant species is relatively common, and occurs relatively often amongst species of animals and plants this has been determined by researchers in the past 10 years, the copy number variation is relatively common amongst animal and plant species THE ANALYSIS OF STRUCTURAL VARIATION The analysis of copy number variation IS A RELATIVELY NEW AREA OF ANALYSIS AND INVESTIGATION though the study and the analysis of structural variation, of copy number variation is a relatively new field of study, researchers have been able to confidently determine that BW 1 AND 10 PERCENT OF A GENOME MAY SHOW CNV within a typical species of an animal or plant it has been confidently determined by researchers that bw 1 and 10 percent of a genome may show copy number variation within a typical animal or plant species bw 1 and 10 percent of a genome of a typical animal or plant species may show the phenomenon of structural variation and copy number variation, this has been confidently determined by researchers the majority of COPY NUMBER VARIATION IS INHERITED the majority of copy number variation is inherited, the majority of copy number variation is inherited and has occurred in the past what kinds of mechanisms bring about the phenomenon of copy number variation? there is a multitude of mechanisms that brings about the phenomenon of copy number variation there is a multitude of mechanisms that brings about and causes the phenomenon of COPY NUMBER VARIATION the following are mechanisms that bring about copy number variation: ONE COMMON CAUSE OF COPY NUMBER VARIATION IS NONALLELIC HOMOLOGOUS RECOMBINATIOn recall what non allelic homologous recombination is non allelic homologous recombination is a phenomenon where there are repeat sequences in a pair of homologous chromosomes, sequences that recognize each other as homologous (and are in fact homologous to one another) these repeat sequences of these homologous chromosomes therefore align with each other in order for crossing over and genetic recombination to occur however, in these repeat sequences on the two homologous chromosomes aligning themselves, they disregard the rest of the chromosomes they are on, and end up aligning nonhomologous regions with other non homologous regions outside of the homologous alignment of the repeat sequences, therefore crossing over bw non homologous regions also occurs THIS TYPE OF EVENT CAN CAUSE A CHROMOSOMAL DELETION OR DUPLICATION, and therefore can alter the copy number of genes non allelic homologous recombination can cause chromosomal deletions and/or duplications, and therefore can alter the number of copies of a particular DNA segment, brining about copy number variation ANOTHER CAUSE OF COPY NUMBER VARIATION- THE PROLIFERATION OF TRANSPOSABLE ELEMENTS the creation and spreading of transposable elements, segments of DNA that are capable of moving through the genome researchers have investigated and proposed that the proliferation and propagation of transposable elements may also cause and bring about copy number variation the proliferation and propagation of transposable elements may increase the overall copy number of DNA segments the overall copy number of DNA segments may be increased due to the proliferation and propagation transposable elements, which can bring about the phenomenon of extra copies of a dna segments amongst particular members of a species, bringing about the phenomenon of copy number variation ANOTHER AND THIRD CAUSE OF COPY NUMBER VARIATION MAY BE errors in DNA replication A THIRD CAUSE OF COPY NUMBER VARIATION may be errors in DNA replication, errors that result in members of a species having fewer or more than the normal expected number of copies of a particular DNA segment, thus bringing about the phenomenon of copy number variation WHAT ARE THE PHENOTYPIC CONSEQUENCES OF CNV how does copy number variation phenotypically affect an organism or an individual how does copy number variation phenotypically affect and impact an organism or an individual in many cases, copy number variation, the phenomenon of copy number variation has NO OBVIOUS PHENOTYPIC CONSEQUENCES in many cases copy number variation has no obvious and identifiable phenotypic consequences however, even though the phenotypic consequences are not obvious and easily identifiable, they are there, as indicated by recent medical research that has been conducted recent medical research that has been conducted is revealing that SOME COPY NUMBER VARIATION IS ASSOCIATED WITH SPECIFIC HUMAN DISEASES recently conducted medical research has concluded that copy number variation is indeed associated with a number of specific human diseases some examples of how copy number variation is associated with a number of specific genetic diseases: PARTICULAR TYPES OF CNV- PARTICULAR TYPES OF COPY NUMBER VARIATION ARE ASSOCIATED WITH: SCHIZOPHRENIA AUTISM CERTAIN FORMS OF LEARNING DISABILITIES particular types of CNV, particular types of copy number variation are associated with SCHIZOPHRENIA, AUTISM, AND CERTAIN FORMS OF LEARNING DISABILITIES particular types of copy number variation are associated with schizophrenia, autism, and particular types of learning disabilities in addition to the association of specific types of copy number variation with schizophrenia, autism, and particular types of learning disabilities, COPY NUMBER VARIATION MAY ALSO INFLUENCE AN INDIVIDUAL'S SUSCEPTIBILITY TO INFECTIOUS DISEASES copy number variation may also influence an individual's susceptibility to infectious diseases what is an example of how cnv can influence an individual's susceptibility to infectious diseases? an example is the HUMAN CCL3 GENE the human CCL3 GENE the human CCL3 gene encodes a CHEMOKINE PROTEIN the human CCL3 gene encodes a CHEMOKINE PROTEIN this CHEMOKINE PROTEIN THAT IS ENCODED BY THE HUMAN CCL3 gene this chemokine protein that is encoded by the human CCL3 gene is involved in IMMUNITY to infectious diseases amongst human population, the copy number of the CCL3 gene that encodes a chemokine protein that is responsibly for immunity ranges from 1 to 6 a given individual may have 1 to 6 copies of the CCL3 gene IN PEOPLE INFECTED WITH HIV HIV- HUMAN IMMUNODEFICIENCY VIRUS individuals infected with HIV, HUMAN IMMUNODEFICIENCY VIRUS, the copy number variation of CCL3 in the individual infected and afflicted with HIV, human immunodeficiency virus, may affect and impact the progression of AIDS in that individual AIDS IS ACQUIRED IMMUNE DEFICIENCY SYNDROME HIV IS HUMAN IMMUNODEFICIENCY VIRUS AIDS IS ACQUIRED IMMUNO DEFICIENCY SYDROME HIV IS HUMAN IMMUNO DEFICIENCY VIRUS in individuals afflicted with HIV, human immunodeficiency virus, the copy number of CCL3, the number of copies of the CCL3 gene they have that encodes chemokine, a protein that influences immunity, may impact the rate at which this individual develops AIDS, which is ACQUIRED IMMUNE DEFICIENCY SYNDROME individuals afflicted with HIV with a higher copy number of the CCL3 gene have more chemokine protein coded for, and therefore showcase a slower advancement of AIDS, they develop and become afflicted with AIDS (ACQUIRED IMMUNE DEFICIENCY SYNDROME) due to the higher number of copies of the CCL3 gene that encodes a chemokine protein that promotes and is responsible for immunity why are researchers INTERESTED IN COPY NUMBER VARIATION researchers are interested in copy number variation in regards to the relationship bw copy number variation and cancer

basically Rosalind Franklin and also those bitches Watson and crick

Watson and Crick deduced the double helical structure of dna Watson and crick deduced the double helical structure of dna Thus far we have examined key pieces of information utilized in order to determine the structure of dna We have examined key pieces of information utilized in order to determine the structure of dna, In particular, the x ray diffraction work implemented by Franklin suggested that the structure of DNA is a helical structure composed of two or more strands (based on the diameter of the helix being so large that a single strand could not possibly fold into a conformation of this diameter), with 10 bases per turn In addition, the work of Chargaff indicated that the amount of A equals T, the amount of the nitrogenous base adenine equals the amount of the nitrogenous base thymine within dna and the amount of the nitrogenous base guanine equals the amount of the nitrogenous base cytosine Watson and crick were also familiar with Pauling's success in the utilization of ball and stick models in order to deduce the secondary structure of proteins, the conformations in which proteins were able to fold, and how all of the atoms sorted themselves out when the conformation changed Watson and crick assumed that dna is composed of nucleotides that are linked together in a linear fashion They also assumed that the chemical linkage bw nucleotides, the chemical bond bw nucleotides is always consistent and the same With these ideas in mind, of the nucleotides always organizing in a linear fashion and the chemical linkage bw these nucleotides organized in a linear fashion always being the same, they tried to build ball and stick models that incorporated the known experimental observations that had been made Because the diffraction pattern suggested the helix due to its large diameter must have two or more strands, a critical question that required an answer was how could the two strands interact with one another In his book, the double helix, James Watson noted that in an early attempt at model building, in an early attempt to construct a model of the double helix of dna, they considerd the possibility that perhaps the negatively charged phosphate groups that compose the backbone of dna, together with magnesium ions, were potentially producing interactions bw the dna backbones, the backbones of the two individual strands this was an incorrect hypothesis Rosalid franklin had produced even clearer x ray diffraction patterns, and these even clearer x ray diffraction patterns had provided a greater amount of detail concerning the relative specific locations of bases and the backbone of dna The x ray diffraction patterns that she developed the even clearer x ray diffraction patterns that she developed had provided a greater amount of detail concerning the relative specific locations of bases and the backbone of dna This major breakthrough made by rosalind franklin suggested that a two strand interaction was helical In their model building, Watson and crick's emphasis shifted to their model of the dna double helix containing the two strands of dna with the backbones facing outside, facing away from one another rather than turning in to one another At first there was a structure considered in which identical bases matched but that was incorrect The final hurdlge was overcome when it was finally understood that the hydrogen bonding of adenine to thymine was structurally similar to the hydrogen bonding of guanine to cytosine With the interaction bw an a and a t and a g and a c, with the interaction bw the nitrogenous base adenine and the nitrogenous base thymine and the interaction bw the nitrogenous base guanine and the nitrogenous base cytosine, the constructed ball and stick models showcased that with these particular interactions and hydrogen bonding bw these particular nitrogenous bases on opposing dna strands would all fit together properly The developed ball and stick model was consistent with all the known, established, and verifiable features of dna structure at the time

mitochondria and chloroplast gene discovery

Yukako Chiba was the first individual to suggest that the organelles, chloroplasts, contain their own DNA he suggested and propose this notion in 1951 his conclusion and proposed notion was due to the staining properties of a DNA-specific dye this DNA specific dye was known as Feulgen there was a developed technique implemented later on that was utilized in order to purify the DNA within organelles, but at this time, there was the utilization of the DNA specific dye Feulgen there were also electron microscopy studies done that provided insight into and knowledge of the organization and composition of the college lions of chromosomes found within mitochondria and chloroplasts using electron microscopy researchers were able to understand the way that mitochondrial and chlorplast chromosomes organize themselves, conglomerate, and interact in the 1970s and 1980s, molecular genetic techniques that were developed allowed researchers to understand and designate the genome sequences that compose the DNA found in organelles such as mitochondria and chloroplasts researchers were therefore able to determine that the chromosomes found within mitochondria and chloroplasts resemble and are alike to smaller versions of bacterial chromosomes (so the chromosomes found within mitochondria and chloroplasts resemble bacterial chromosomes, but are found in a smaller size) the DNA within mitochondria and chloroplasts is found within the nucleoid region of these organelles the genome (the entirety of the genetic material) is a single circular chromosome this single circular chromosome is composed of double stranded DNA however, within the nucleoid region, there are several copies of this chromosome a mitochondria or chloroplast often times contains more than one nucleoid within mice and their mitochondria, each one of their mitochondria contain 1-3 nucleoids (1-3 nucleoid regions) each nucleoid within their mitochondria contain 2-6 copies of the circular mitochondrial genome (the entirety of the mitochondria's genetic material) there are 2-6 copies of the entirety of the mitochondrial genome (the circular mitochondrial genome) due to the 1-3 nucleoids present in each mouse's mitochondria the number of nucleoids and the number of copies of the circular mitochondrial genome change from organism to organism, change from the type of cell you are looking at, as well as the stage of development that the cell is at in comparison, looking at the chloroplasts of algae and higher plants : the chloroplasts of algae and higher plants tend to have more nucleoids within them (more nucleoids per organelle) and therefore more copies of the circular genome of these organelles

gene

a "unit of heredity" that may influence the outcome of an organism's traits (the way it presents morphologically, physiologically, and behaviorally) all of the seven characters studied by Mendel are influenced and governed by different genes

distinguishing bw character and trait/variant

a character (a general characteristic of an organism) would refer to the eye color a trait/variant of that general characteristic would be blue eyes, a specific trait found amongst particular individuals

chi square analysis

a chi square analysis can be utilized in order to distinguish bw linkage and independent assortment a chi square analysis can be utilized in order to distinguish bw linkage and independent assortment a chi square analysis can be utilized in order to distinguish bw linkage and independent assortment a chi square analysis can be utilized in order to distinguish bw linkage and independent assortment now that we have an appreciation for and understanding of linkage and the production of recombinant offspring, how genetic linkage influences the production of non parental and recombinant offspring, let us try and consider how an experimenter can objectively and verifiably determine whether two genes are linked to one another or independently assorted from one another and not linked in chapter 2, we utilized chi square analysis in order to evaluate the goodness of fit bw a genetic hypothesis and observed experimental data in chapter 2, we utilized a chi square analysis in order to evaluate the goodness of fit bw a genetic hypothesis put forth by a scientist and observed experimental data in chapter 2 we utilized a chi square analysis in order to determine the goodness of fit bw a proposed genetic hypothesis and the observed experimental data in chapter 2 we utilized a chi square analysis in order to determine the goodness of fit bw a proposed genetic hypothesis and observed experimental data this method of a chi square analysis can similarly be employed to determine if the outcome of a dihybrid cross is consistent with genetic linkage or independent assortment this method of a chi square analysis can be similarly utilized in order to determine if the outcome of a dihybrid cross, involving two different characters and following their inheritance pattern is consistent with the law of independent assortment or genetic linkage in order to conduct a chi square analysis, we must first propose a hypothesis for particular traits and the pattern of inheritance we believe they will generally follow in a dihybrid cross, where we are following the inheritance patterns of two traits, the standard hypothesis for a dihybrid cross is that the two genes coding for the two traits that the dihybrid cross is following the inheritance patterns of are not linked with one another, and therefore will follow the law of independent assortment and showcase a ratio in the f2 generation that is consistent with the law of independent assortment it is generally assumed with a dihybrid cross that the two traits/characters that are being followed, the genes that codes for these two traits/characters being followed are not linked, and will follow the law of independent assortment during gametogenesis this hypothesis of the two genes coding for the two traits/characters that the dihybrid cross is following being unlinked and therefore following the law of independent assortment and being independently assorted even if the observed experimental data suggests genetic linkage bw two genes why is this hypothesis that the two genes encoding the two characters that the dihybrid cross is following are unlinked and follow the law of independent assortment and are independently assorted even when the experimental data suggests that these two genes that are coding for characters that the dihybrid cross is following are indeed linked to one another and therefore do not follow the law of independent assortment why is the hypothesis regardless of the suggestion/implication of the observed experimental data is always that the two genes coding for the characters that the experiment, the dihybrid cross is following are unlinked and follow the law of independent assortment this hypothesis of the two genes coding for the characters/traits that the dihybrid cross or the experiment is following are unlinked and follow the law of independent assortment, this hypothesis is always proposed even if the observed experimental data suggests otherwise because an independent assortment hypothesis the hypothesis that two genes are unlinked and are sorted independently from one another, this hypothesis of independent assortment allows us to calculate the expected number of offspring based on the genotypes of the parents this proposed, this consistently proposed hypothesis of independent assortment allows the experimenter to be to calculate the expected number of offspring based on the genotypes of the parents and the law of independent assortment coming into play the hypothesis of independent assortment for the two genes allows the experimenters to calculate the expected numbers of offspring based on the genotypes of the parents and the implementation of the law of independent assortment in regards to these two genes that independently assort from one another in contrast, for two linked genes that have not been previously mapped (meaning we do not yet have an established understanding of whether or not these genes are linked, and they have not been mapped to allow us to understand the expected numbers of offsprings based on the genotypes of the parents and genetic linkage coming into play) the experimenter cannot hypothesize the phenomenon of genetic linkage, because hypothesizing the phenomenon of genetic linkage without those genes having been already proven as linked, and genetically mapped to provide us with a numerical structure from which we can calculate the expected numbers of offspring based off of the genotypes of the parents and the phenomenon of genetic linkage coming into play, we cannot calculate the expected numbers o offspring from a genetic cross, bc without those two genes being genetically mapped, we do not know the physical distance bw those two genes and therefore do not know the likelihood of a crossover occurring bw these two genes without the expected numbers of recombinant and parental offspring, which we are unable to calculate if a hypothesis of genetic linkage is proposed, bc if those two genes have not been mapped before, the distance bw them is unknown, and it is unknown what the probability of crossing over bw those genes, which leads to recombinant and non parental phenotypic combinations is, without the expected numbers of recombinant and parental offspring, an experimenter is not able to conduct a chi square test to determine whiter the outcome of a dihybrid cross is due to the law of independent assortment or genetic linkage therefore, we begin with the hypothesis that the two genes whose characters they code for that we are following through the implementation of a dihybrid cross are not linked, and follow the law of independent assortment the hypothesis that we are testing is called a NULL HYPOTHESIS the hypothesis that we are testing is called A NULL HYPOTHESIS the hypothesis that we are testing is called a NULL HYPOTHESIS the hypothesis that we are testing is called a NULL HYPOTHESIS why is the hypothesis that we are testing called a null hypothesis it is called a null hypothesis because this hypothesis assumes there is no real difference bw the observed experimental values and the expected values this hypothesis assumes that there is no real difference bw the observed experimental values and the expected values the goal is to determine whether or not the observed experimental data fits the hypothesis if the chi square value is low, and therefore we are unable to reject the null hypothesis, the hypothesis that presumes that there is no real difference bw the observed experimental data and the expected data, we infer that the genes do indeed assort independently, bc the chi square value is low that we are unable to reject the null hypothesis (the hypothesis presuming and proposing that there is no real difference bw the observed and expected data) that the genes are unlinked and follow the law of independent assortment, we assume that the hypothesis is indeed correct, and the genes are indeed unlinked, and follow the law of independent assortment, sorting themselves independently on the other hand, if the chi square value is so high that our hypothesis of the two genes being unlinked and following the law of independent assortment is rejected, we accept the alternative hypothesis, the hypothesis that the genes are indeed linked to one another and therefore follow alongside the phenomenon of genetic linkage OF COURSE A STATISTICAL ANALYSIS CANNOT PROVE THAT A HYPOTHESIS IS TRUE a statistical analysis cannot prove that a hypothesis is true a statistical analysis cannot prove that a hypothesis is true a statistical analysis cannot prove that a hypothesis is true a statistical analysis cannot prove that a hypothesis is true a statistical analysis such as the chi square test cannot prove that a hypothesis is true if the chi square value is high, we reject our hypothesis of independent assortment and accept the hypothesis of genetic linkage because we are assuming that the only two explanations for a genetic outcome are possible: the genes are either linked or not linked if the chi square value is high, we reject our proposed hypothesis of the two genes following the law of independent assortment and being unlinked and accepting the hypothesis of the two genes being linked and influenced by the phenomenon of genetic linkage bc we are assuming that the only two explanations for a genetic outcome are that the genes are linkedd or not linked however, if there are other factors that affect the outcome of the crossed, such as a decreased viability of particular created phenotypes if there are other factors that affect the outcome of the cross, such as a decreased viability of a particular phenotypic outcome/combination, these additional factors may result in large deviations bw the observed and expected values, and cause us, to do the high chi square value calculated due to the substantial difference in observed and expected values, to reject the hypothesis of independent assortment, even though this assortment may be correct, and our chi square value determining a substantial difference bw the observed and expected values may have been so high due to an outside factor, such as a decreased viability of a particular phenotypic outcome/combination in order to carry out a chi square analysis, we need to reconsider the data concerning body color and eye color in order to carry out a chi square analysis, we need to reconsider the data concerning body color and eye color in ordre to carry out a chi square analysis, we need to reconsider the data concerning body color and eye color this cross produced the following offspring: 1159 gray body, red eyes- parental and nonrecombinant 1017 yellow body, white eyes- parental and nonrecombinant 17 gray body, white eyes- nonparental and recombinant 12 yellow body, red eyes- nonparental and recombinant however when there is a heterozygous female containing heterozygous allelic combinations for the genes coding for body color and eye color (Xy+w+Xyw, ultimately coding for gray body color and red eyes) is crossed to a hemizyogus recessive male for the genes coding for body color and eye color (Xyw, ultimately coding for yellow body color and white eyes), the laws of segregation and independent assortment predict the following outcome the only possible male gamete contribution is an X chromosome with the allelic combination Xyw to a female offspring, as a female offspring requires one x chromosome inherited from the mother and one X chromosome inherited from the father the other possible male gamete contribution is a Y chromosome to the male offspring which always inherit the Y chromosome of their sex chromosome composition/combination of XY from the father this Y chromosome, the y chromosome within fruit flies does not carry any of these genes, does not carry the genes coding for body color or eye color, and therefore this contributed y chromosome in male offspring will not have any impact on the genotype or the phenotype of the male offspring in regards to the genes coding for body color and eye color, and the phenotypic traits of the male offspring in regards to body color and eye color there are 4 possible gametes that the heterozygous female fruit fly can create there are 4 possible gametes that the heterozygous female fruit fly can contribute to its offspring each offspring both male and female will only inherit 1 x chromosome from the mother the four possible gametes that the heterozygous female fruit fly can contribute to its offspring include: Xy+w+ Xy+w Xyw+ Xyw these four possible gametes can be contribute to the offspring, both male and female by the female fruit fly the female offspring will inherit a single X chromosome from the mother and a single x chromosome from the father the resulting potential phenotypes of the offspring are the following: Xy+w+Xyw- this is a heterozygous female fruit fly with a gray body, red eyes Xy+wXyw- this is a female fruit fly that is heterozygous for the gene coding for body color and homozygous recessive for the gene coding for eye color, this female fruit fly has a gray body, and white eyes Xyw+Xyw- this is a female fruit fly that is homozygous recessive for the gene coding for body color, and heterozygous for the gene coding for eye color, therefore this female offspring has a yellow body and red eyes XywXyw- this is a female fruit fly that is homozygous recessive for the gene coding for body color and homozygous recessive for the gene coding for eye color, and therefore this female fruit fly offspring has a yellow body and white eye color Xy+w+Y- this is male fruit fly that is hemizygous for the gene coding for body color and the gene coding for the eye color, meaning that the allele that it has inherited on its X chromosome from its mother will be the genetic determinant for the phenotypic characteristic of that gene that it displays because this male fruit fly offspring has the dominant allele for body color and the dominant allele for eye color, it has a gray body and red eyes Xy+wY- this is a male fruit fly offspring that has the dominant allele for the gene coding for body color, and the recessive allele for the gene coding for eye color, and therefore this male offspring has a gray body color and white eyes Xyw+Y- this male fruit fly has the recessive allele for the gene coding for body color, and the dominant allele for the gene coding for eye color, and therefore this male fruit fly has a yellow body and red eyes XywY- this is a male fruit fly, and it has the recessive allele for the gene coding for body color and the recessive allele for the gene coding for eye color, and therefore this male fruit fly has a yellow body and white eyes Mendel's laws of segregation and independent assortment predict a 1:1:1:1 ratio amongst the four phenotypes Mendel's laws of segregation and independent assortment predict a 1:1:1:1 ratio amongst the four phenotypes the observed data seem to conflict with this expected outcome nevertheless, we stick to the strategy that we just discussed, of proposing that the two genes are unlinked and follow the laws of segregation and independent assortment even when the observed data seems to conflict this claim we begin with the hypothesis that

gene interactions

a common way to try and understand genes is studying the effects of a single gene on the outcome of a single trait this simplified approach helps us in understanding the variety of relationships bw genes and phenotypic expressions of trait the study of a single gene and its effect on the outcome of a single trait is a method employed by many genetics researchers in order to simplify the genetic analysis in Mendel's conducted studies, he studied only a single gene that impacted the height of pea plants (that influenced the phenotypic expression of height) he looked at alleles coding for tall, and alleles coding for short however there are a multitude of genes that impact height, genes that Mendel did not study the variants of how was Mendel able to study the trait of height and how it is impacted by one individual gene? he was able to accomplish this by the genotypes he utilized in his crosses essentially, what he made sure was that the two plants he crossed differed only in the exact gene he was studying, and were identical throughout the rest of their genotypes so if the rest of the genes are the exact same bw the two plants you are crossing, than the only thing that can cause them to be different is the gene you are examining, and that will be the only influence on the phenotypic characteristics shown by the offspring of that cross ensuring that the two plants are genetically identical except for one gene narrows the possibilities of genetic determinants for variation in a trait down to a single gene, despite the other genes also having an influence on that trait (bc the genes of the two plants being crossed have the exact same allelic combination in all genes but one, all those other genes that can affect that trait are controlled for, where the only genetic difference bw the two is found in one gene, and therefore that gene must be responsible for any variation you see in the parental generation, and upcoming variation

Hippocrates

a famous Greek physician he tried to take a crack at the explanation for hereditary traits, traits that are passed on from parent to offspring he came up with the term pangenesis pangenesis hypothesizes that all parts of the body produces seeds, then these seeds are collected and transmitted to the produced offspring by conception these seeds apparently cause particular traits of the offspring to resemble the parental traits

incomplete dominance (expanded definition)

a heterozygote is the kind of individual that exhibits incomplete dominance incomplete dominance is a condition where the phenotype is an intermediate bw the corresponding homozygotes, the phenotype expressed by the homozygous dominant individual and the homozygous recessive individual this phenomenon of intermediate dominance was first observed in 1905 by the German botanist Carl Correns this scientist observed the color of the four o'clock flower- Mirabilis Jalapa Corren's experiment- look at notes incomplete dominance in this experiment resulted in a heterozygous organism exhibiting an intermediate phenotype of pink, falling right in bw the two phenotypes of the homozygotes, red and white molecular explanation: the allele that codes for the white flower phenotype is expected to result from a lack of a functional protein required for that red pigmentation due to the protein not functioning properly and coding for red pigmentation, there is a lack of red pigment, and therefore the phenotype expressed is white heterozygotes of this organism have 50 percent of the normal protein for red pigmentation produced, but that amount is not enough for the flower to express a red phenotype, there probably is a requirement of more than 50 (probably 100) recent protein production in order for this organism to express the red phenotype therefore the heterozygous organism does not produce the same phenotype as the Cr Cr homozygote 50% of the functional protein coding for pigment cannot produce the same result (the same amount of red pigment/phenotypic expression) that 100% of the protein is able to

aneuploidy

a second way in which chromosome number can vary is by aneuploidy ANEUPLOIDY IS A SECOND WAY IN WHICH CHROMOSOME NUMBER CAN VARY polyploidy had to do with the total number of chromosomes, the total number of sets of chromosomes in particular, how many sets of chromosomes that an organism has within its genome HOWEVER aneuploidy is a different kind of chromosomal variation, and aneuploidy involves an alteration in the number of particular chromosomes, so that the total number of chromosomes is not an exact multiple of set aneuploidy is type of difference in chromosome number that has to do with alteration in the numbers of particular chromosomes within a set, an alteration in the number of copies of particular chromosomes within a set of chromosomes, where the total number of chromosomes within that aneuploid organism is not a multiple of a chromosomal set, due to there being an alteration in the number of particular chromosomes, not an addition or subtraction of an entire set of chromosomes an example of aneuploidy is an abnormal fruit fly, but with a different type of alteration in chromosome number in this abnormal fruit fly with aneuploidy, it contains 9 chromosomes instead of the requisite 8 chromosomes because it has three copies of a particular type of chromosome, three copies of chromosome 2, instead of the normal two copies of chromosome 2 therefore the total number of chromosomes within this fruit fly with aneuploidy is not a multiple of a single set of chromosomes, 9 is not a multiple of 4 however the organism, the abnormal fruit fly has more chromosomes than is normal, because this fruit fly has three copies of a particular chromosome, 3 copies of chromosome 2 this animal, this abnormal fruit fly organism is said to have trisomy 2 or TO BE TRISOMIC instead of this organism being perfectly diploid, 2n, a trisomic animal, a trisomic organism is 2n+1 this abnormal fruit fly organism is said to have trisomy 2 or to be trisomic instead of this organism being designated as perfectly diploid and 2n, with two sets of chromosomes, it is designated as trisomic, 2n+1 as it has two sets of chromosomes, plus an extra copy of chromosome 2, an extra copy of a particular chromosome that changes the total number of chromosomes in this abnormal fruit fly genome, making it noneuploid as well because 9 is not a multiple of a single drosophila melanogaster chromosome set which consists of 4 chromosomes by comparison, another fruit fly could also have aneuploidy in the other direction in regards to total amount of genetic material a fruit fly could be lacking a copy of one of its chromosomes, such as chromosome 1, and therefore instead of containing the requisite number of 8 chromosomes within its genome, contain simply 7 chromosomes due to it missing a copy of one of its chromosomes this would be designated as a monosomic individual, and the designation would be 2n-1, as it would have 2 sets of chromosomes minus 1 chromosome missing ANEUPLOIDY IS GENERALLY REGARD AS AN ABNORMAL CONDITION aneuploidy is generally regarded as an abnormal condition that usually has a negative effect on phenotype aneuploidy is generally considered an abnormal chromosomal genetic condition that usually has a negative effect on the phenotype of the organism with aneuploidy THE PHENOTYPE OF EVERY EUKARYOTIC SPECIES IS INFLUENCED BY THOUSANDS OF DIFFERENT GENES the phenotype of every eukaryotic species is influenced by thousands of different genes the phenotypic of every eukaryotic species is influenced and impacted by thousands of different genes, thousands of different genes influence and impact the phenotype of eukaryotic species the phenotypes of eukaryotic species are influenced and impacted by thousands of different genes within the human population, a single set of chromosomes contains approximately 20,000 to 25,000 different genes within the human population, a single set of chromosomes contains approximately 20,000 to 25,000 different genes in order to produce a phenotypically normal individual intricate coordination has to occur in the expression of thousands of genes in order for the production of a phenotypically normal offspring to occur, there must be an intricate coordination within the expression of tens of thousands of genes there must be an intricate coordination of tens of thousands of genes in order for the production of a phenotypically normal offspring to occur there must be an intricate coordination of tens of thousands of genes that occurs in order for the production of a phenotypically normal offspring to occur in the case of humans and other diploid species, that have two sets of chromosomes, a requisite number of two sets of chromosomes, evolution has resulted in a particular developmental process a particular developmental process has resulted due to evolution with humans and other diploid species there is a developmental process that has resulted from evolution that works correctly when somatic cells each have 2 copies of each type of chromosome this developmental process resulting from evolution works when all somatic cells have two copies of each type of chromosome, 2 copies of each chromosome in other words when a human is diploid, the balance of gene expression that occurs amongst those tens of thousands of genes occurs, due to the presence of 2 copies of each type of chromosome, and the organism is able to successfully develop and present as a phenotypically normal individual, due to each of its somatic cells (particularly the ones that formed its zygote and continued as the embryo developed) contain 2 copies of each type of chromosome

genomic imprinting example

a very specific example we are looking at a mouse within this mouse that we are researching, we are looking at a gene designated as Igf2 this gene Igf2 codes for a protein growth hormone this protein growth hormone that the gene Igf2 codes for designated as insulin-like growth factor 2 how does genomic imprinting occur with this gene Igf2 that goes for an insulin-like growth factor 2? imprinting occurs, and results in the expression of the paternally inherited allele of the Igf2 gene being expressed, and the maternally inherited allele of the Igf2 gene not being expressed how is one allele (the paternally inherited one) expressed and the other is not? the paternal allele (the DNA encoding this paternally inherited allele of the Igf2 gene) is transcribed into RNA while the maternal allele (the DNA encoding this maternally inherited allele of the Igf2 gene) is not transcribed the paternal allele is transcriptionally expressed and the maternal allele is transcriptionally silent a functional Igf2 gene is required in order for the mouse to phenotypically express a normal morphological size there is a loss-of-function allele for the Igf2 gene and this allele is known as Igf2- it codes for a loss of function in the synthesis of a functional Igf2 protein (the production of this protein leads to the mouse presenting with a normal size, and the loss of function allele codes for the loss of synthesis of this protein, which will cause the mouse to be dwarf) the mouse can be dwarf if this loss of function allele is present in the allelic combination of their Igf2 gene, but it is dependent on whether the loss of function allele Igf2- was paternally or maternally inherited (as the paternally inherited allele is the one that will be marked, transcriptionally expressed, and will function as the determinant of the production of the Igf2 protein and therefore the size of the mouse) look through notes on the Igf gene crosses bw individuals with different genotypes and resulting phenotypes: bw two true breeding individuals where the female is affected and has the two loss of function alleles Igf2- coding for itself having a dwarf size, and the male is unaffected and homozygous for the normal, dominant, wild-type allele coding for normal size, where all of the offspring have a heterozygous genotype, one maternally inherited loss of function allele coding for the Igf2 gene w the Igf2- allele that codes for the phenotypic expression of dwarfness, and the paternally inherited normal, dominant wild type allele, Igf2 coding for the phenotypic expression of normal size, and the paternal allele is the sole genetic determinant of the genotypic and phenotypic expression of the offspring the second cross is bw a female that is homozygous for the normal, dominant, wild-type allele Igf2 coding for normal size, and a male that is homozygous for the loss of function allele Igf2- coding for a dwarf size the offspring of this cross are all heterozygous with a maternally inherited allele of the dominant, normal, wild-type Igf coding for normal size, and the paternally inherited allele, the recessive and loss of function allele, Igf2- coding for the phenotypic expression of dwarfness all of the offspring phenotypically present as dwarf, due to the paternally inherited allele being the sole genetic determinant of the phenotypic thatchy express due to genomic imprinting with genomic imprinting, only one particular preselected allele is expressed, and within mice and the Igf2 gene coding for size, only the paternally inherited allele in the offspring's allelic combination is ever expressed, therefore the paternally inherited allele is the sole genetic determinant of the size of the mouse

abnormal crossover

abnormal crossover is a second mechanism that can can cause a translocation abnormal crossover is a second mechanism that can cause a translocation A RECIPROCAL TRANSLOCATION CAN BE PRODUCED WHEN TWO NONHOMOLOGOUS CHROMOSOMES CROSSOVER a reciprocal translocation can be produced when two non homologous chromosomes during prophase I of meiosis I crossover one another, two non homologous chromosomes, so chromosomes from different and distinct homologous pairs that are not homologous to one another crossing over this particular kind of crossover bw nonhomologous chromosomes can result in a translocation, specifically a reciprocal translocation THIS TYPE OF RARE ABERRANT EVENT this type of rare chromosomal aberration, where there is a translocation of genetic material in two directions, a reciprocal translocation type of chromosomal aberration that affects two chromosomes, this type of rare aberrant event results in the rearrangement of genetic material this type of rare aberrant event, a reciprocal translocation resulting from crossing over occurring bw two nonhomologous chromosomes during prophase I of meiosis I causes a rearrangement of genetic material, but does not result in the loss or gain of any genetic material there is no change in the totality of genetic material the total amount of genetic material does not change, the genetic material is simply rearranged due to the chromosomal aberration of a reciprocal translocation that occurs when two nonhomologous chromosomes undergo a crossover with one another during prophase I of meiosis one

adjacent 2 segregation

adjacent 2 segregation is the final form of segregation, haploid gamete development that can occur when an individual who has balanced translocations in its genetic material throughout all of its somatic cells develops and forms gametes adjacent 2 segregation happens on v rare occasions on v rare occasions, adjacent 2 segregation can occur in this case, the centromeres do not segregate as they should during anaphase I of meiosis, the pairs of sister chromatids segregate in a way similar to the way that the pairs of sister chromatids segregate in adjacent 1 segregation BUT THERE IS A DIFFERENCE the difference is that one daughter cell inherits both copies of the centromere of chromosome 2, meaning that they inherit almost 2 pairs of sister chromatids containing the genetic material of chromosome 2, rather than 1 pair of sister chromatids containing the genetic material of chromosome 2, and the other pair of sister chromatids containing the genetic material of chromosome 1 in one of the daughter cells that comes out of meiosis I, there is an excess of chromosome 2 genetic material, and a deficiency of chromosome 1 genetic material, bc the segregation of pairs of sister chromatids did not occur properly then in the second daughter cell, there are almost 2 pairs of sister chromatids containing solely the genetic material of chromosome 1, and almost no genetic material from chromosome 2 therefore within this daughter cell, also due to the pairs of sister chromatids not separating properly during meiosis I, this daughter cell has an excess of the genetic material of chromosome 1, and a deficiency of the genetic material of chromosome 2 however, the difference continues to come in anaphase 2 of mitosis, when these pairs of sister chromatids split and are subsequently recognized as individual chromosomes THE CENTROMERES DID NOT SEGREGATE AS THEY SHOULD the result of the centromeres not segregating as they should, results in two daughter cells with an excess of chromosome material and a deficiency of the chromosomal material of another chromosome, and this results in 4 genetically unbalanced haploid cells two haploid cells have developed from the daughter cell from meiosis I, which had an excess of chromosome 1 material, and a deficiency of chromosome 2 material due to the centromeres not segregating properly as they should during anaphase I of meiosis I in order to organize the pairs of sister chromatids, and which pairs go into which cell these two haploid cells that developed from the daughter cell with an excess of chromosome 1 material and a deficiency of chromosome 2 material, also have a excess chromosome 1 material and a deficiency of chromosome 2 material they contain almost 2 chromosome 1's, almost 2 copies of chromosome 1 (which as gametes, they should only have one), and almost no copy of chromosome 2, which shows both a duplication and deletion there are two other haploid gametes two other haploid cells that develop from the other daughter cell that contained an excess of chromosome 2 genetic material and a deficiency of chromosome 1 genetic material these two haploid cells maintain the excess and the deficiency, containing almost 2 copies of chromosome 2 each, and almost no copy of chromosome 1, showcasing dangerous duplications and deletions there is an unbalanced combination of chromosomes in each haploid cell that develops from adjacent-2- segregation THE MOST LIKELY OUTCOMES WHEN AN INDIVIDUAL CARRIES A BALANCED AND RECIPROCAL TRANSLOCATION are alternate and adjacent 1 segregation, these are the most common depending on the sizes of the translocated chromosomal segments, both types may be equally likely to occur and both more likely to occur than adjacent 2 segregation in the majority of cases THE HAPLOID CELLS FROM ADJACENT 1 SEGREGATION ARE NOT VIABLE due to genetic imbalances in all of the produced gametes that will most likely cause phenotypic consequences in the offspring that develops from any zygote formed by these gametes, due to the genetic imbalance within these gametes, inherited imbalanced translocations, the zygotes formed by these gametes, the zygotes whose formation is contributed to by and composed of these genetically unbalanced gametes are not viable, which will lower the fertility of the parent the gametes produced from alternate 1 segregation are not viable for fertilization, and therefore this lowers the fertility of the parents when their gametes are formed from adjacent 1 segregation this condition of lowered fertility is designated as semisterility

adjacent-1-segregation

adjacent-1-segregation is another type of segregation pattern adjacent-1-segregation is another type of segregation pattern, another possible segregation pattern that can occur when an individual containing a translocation a chromosomal translocation within all of its somatic cells produces gametes the first type of segregation was alternation segregation, where with the formation of the translocation cross, being composed of 8 sister chromatids, 4 pairs of sister chromatids, 2 pairs being affected by a chromosomal translocation, and the other 2 pairs of chromosomes being completely normal, could potentially lead to alternate segregation in alternate segregation, the two sister chromatid pairs located across from one another are sorted into the same cell during meiosis I anaphase I of meiosis I will separate the translocation cross consisting of 4 pairs of sister chromatids into 2 separate cells, placing the pairs of sister chromatids located diagonally across from one another in the same cell this will result in two cells from meiosis I, where there will be 1 cell containing the 2 normal pairs of sister chromatids, the 2 normal pairs that were not impacted by a translocation the other cell resulting from meiosis I will contain the two pairs of sister chromatids that were affected by translocations then, though the progression and completion of meiosis II, there will be two haploid cells each individual containing 2 normal chromosomes, one from each normal pair of sister chromatids then there will be two haploid cells contain 2 abnormal chromosomes, 1 from each abnormal pair of sister chromatids that were affected by translocation however, these will be balanced translocations, where there is rearrangement of the genetic material in these cells, these gametes have rearranged genetic material, but the totality of the genetic material remains the same, bc there are balanced translocations, where material has been moved around, but the total amount of genetic material has not been altered in adjacent-1-segregation, this is another possibility that could occur in regards to gamete formation of an individual with a translocation in its genetic material, a translocation that is reflected throughout all of its somatic cells when does this occur adjacent 1 segregation occurs when adjacent chromosomes (ONE OF EACH TYPE OF CENTROMERE, meaning one centromere from chromosome 1 and one centromere from chromosome chromosome 2) segregate into the same cell chromosomes within the translocation cross that are adjacent to one another segregate into the same cell so chromosomes, pairs of sister chromatids that are adjacent to one another in the translocation cross a structure/conglomeration composed of 4 pairs of sister chromatids, making for a total of 8 sister chromatids are sorted into the same cell, and they contain a centromere from each type of chromosome altogether, one pair of sister chromatids containing the centromere from one type of chromosome, and the other pair of sister chromatids containing the centromere from the other type of chromosome this sorting of adjacent chromosomes within the translocation cross into the same cell means that an abnormal pair of sister chromatids that has undergone a translocation, and a normal pair of sister chromatids that has not undergone a translocation, are sorted into the same cell due to the implementation of anaphase I of meiosis I each daughter cell receives one translocated chromosome and one normal chromosome due to the occurrence of adjacent 1 segregation once meiosis ii occurs aligned with adjacent-1 segregation, there are 4 haploid cells that come about, which is normal for meiosis, when meiosis II is implemented and completed, there are 4 haploid cells created at the end ALL OF THESE 4 HAPLOID CELLS ARE GENETICALLY IMBALANCED all of these 4 haploid cells are genetically imbalanced ALL OF THESE 4 haploid cells that come out of adjacent 1 segregation are GENETICALLY IMBALANCED the amounts of genetic material within these haploid cells are altered and incomplete in each haploid cell, due to the events of anaphase I of meiosis I where adjacent pairs of sisters chromatids in the translocation cross were sorted into the same cell, resulting in both cells each containing 1 normal pair of sister chromatids and 1 pair of sister chromatids that had undergone translocation, due to these events of meiosis I, these haploid cells each contain chromosomes where part of one chromosome has been deleted, and part of the other chromosome has been duplicated there are 2 cells created containing 1 full chromosome 2, and a duplication of the genetic material of chromosome 2 in the other chromosome, and a deletion of chromosome 1 genetic material therefore there is a chromosome 2 genetic material excess, and a chromosome 1 genetic material deficiency in the other 2 haploid cells created due to adjacent 1 segregation, these also contain chromosomes where part of one chromosome is deleted and part of another chromosome is replicated in each of these haploid cells, there is 1 complete chromosome 1, and then duplicated genetic material of chromosome 1 on the second chromosome, where there is also a deletion of genetic material of chromosome 2 therefore in these cells there is an excess of chromosome 1 genetic material, and a deficiency of chromosome 2 genetic material if these haploid cells give rise to gametes that unite with a normal gamete due to fertilization, the resulting zygote created from this fertilization is expected to have unbalanced translocations in their chromosomes, and therefore abnormal morphological, physiological, or behavioral traits and phenotypic consequences due to these unbalanced translocations in their genetic material, that impacts the totality of genetic material and therefore has an impact on the organism in regards to its genotypic and subsequent phenotypic expression

further investigation

after the Lyon hypothesis was confirmed, the genetic control of X inactivation (how genotypes and genes influence the process of X inactivation) has been further investigated and researched by multiple laboratories further research that has been done due to the confirmation and verification of the Lyon hypothesis has concluded that within mammals, mammalian cells have the ability to have the X chromosomes within their cells counted, and have one of them inactivated throughout cell proliferation the observation and conclusion of this about mammals occurred due to comparisons done bw the chromosome compositions of individuals with normal or abnormal numbers of sex chromosomes, and the level of gene expression of each of them within normal females, they have the allelic combination XX, and one of these X chromosomes is inactivated within normal males, they have the allelic combination XY, and the X chromosome is not inactivated within females with Turner syndrome (where they look unusually young for their age throughout their life, noticeably younger physiologically, morphologically despite being older) have the allelic combination X0, where they are missing one X chromosome, and therefore no X chromosome is inactivated within females with triple X syndrome have the allelic combination XXX, and 2 of these X chromosomes are inactivated within males with Klinefelter syndrome, they have the allelic combination XXY, and one of these X chromosomes is inactivated X inactivation occurs in order to implement dosage compensation

the effects of genes on traits

all traits are affected by a multitude of genes the following morphological features (and more) are impacted by the expression of a multitude of genes as well as environmental factors: -height -weight -growth rate -pigmentation

allodiploids are often sterile, allotetraploids are more likely to be fertile

allodiploids are often sterile, but allotetraploids are more likely to be fertile geneticists are interested in the production of alloploids and allopolyploids as a way to generate interspecies hybrids with desirable traits geneticists are interested in and intrigued by the production of alloploids and allopolyploids as a way to generate interspecies hybrids with desirable traits geneticists are interested in the production of alloploids and allopolploids in order to generate interspecies hybrids, hybrids of multiple species with desirable and advantageous traits an example is where there is one species of grass that is able to withstand hot temperatures then there is a closely related species of grass that is adapted and able to survive cold winters, a plant breeder may attest to produce an interspecies hybrid (that will end up being alloploid or allopolyploid) that combines the two qualities of these individual yet closely and evolutionarily related species of plants, to create an interspecies hybrid that is able to withstand both hot and cold weather, a new advantageous combination of the two previously individual and distinct traits, good growth in heat, and survival through the winter an alloploid may be desirable, an alloploid with these two characteristics due to being an interspecies hybrid combining the traits of growing well in heat and surviving winter, may be advantageous and desired in areas with climates consisting of hot summers and cold winters, because this plant would both grow well and survive, being able to adapt to these two polar temperatures an important determinant of success in producing a fertile allodiploid is the degree of similarity of the different species' chromosomes, just how closely evolutionary related these two species are, and how similar their chromosomes are these characteristics, how closely evolutionary related two species are and how similar the two sets of chromosomes from the two different species are are both important determinants in regards to whether the resulting offspring will be fertile or not there is a karyotype of an interspecies hybrid bw the roan antelope, a hippotragus equines, and the sale antelope, the hippotragus niger as seen here, these two closely related species have the same number of chromosomes within their genomes, the size and banding patterns of these chromosomes sho that these chromosomes correspond to one another these sets of chromosomes are indeed from different species, but the chromosomes do correspond to one another in regards to both size and banding pattern, assisting along with the fact that these two species are closely evolutionary related toone another an example of how these chromosomes closely correspond to one another (and how that might influence fertility in an offspring created by organisms from these two closely evolutionarily related species) chromosome 1 from both species is fairly large, has very similar banding patterns, and carries many of the same genes evolutionarily relate chromosomes from two different species are designated at homeologous chromosomes they are designated as homeologous chromosomes homeologous chromosomes are two evolutionary related chromosomes from two different species homologous chromosome are evolutionary related chromosomes from two different species they are not to be confused with homologous chromosomes this allodiploid created by two organisms that are closely evolutionary related, the roan antelope (hippotragus equines) and the sale antelope (hippotragus niger) due to these two species being v closely evolutionary related and the chromosomes of these two species being homeologous chromosomes, being closely evolutionary related chromosomes that belong to the same species, with similar or the same size, banding patterns, and genes, is fertile because the homeologous choromsomes, the closely evolutionarily related chromosomes from the two different species being similar or the same size, with similar or the same banding patterns and genes can properly synapse during meiosis I to produce haploid gametes this allodiploid is fertile the critical relationship bw chromosome pairing and fertility was first recognized by a Russian cytogeneticists the critical relationship bw chromosome pairing and fertility was first recognized by a Russian cytogeneticist named Georgi Karpechenko in 1928 he crossed a radish (raphanus) and a cabbage (brassica) both of which are diploid, containing two sets of chromosomes, and contain a total of 18 chromosomes so he crossed a radish and a cabbage, both of which are diploid, containing two sets of chromosomes and they both the radish and the cabbage contain a total of 18 chromosomes however, becasue the radish and the cabbage are not closely related species, because the radish the raphanus and the cabbage the brassica are not closely related are not closely evolutionarily related, the nine raphanus radish chromosomes are distinctly different form the nine brassica radish chromosomes the nine types of radish raphanus chromosomes that are found within a single set are not closely related and are distinctly different from the nine types of cabbage brassica chromosoems found in a single set during meiosis I, the chromosomes of the raphanus raddish and the chromosomes of the brassica cabbage are not able to synapse with one another the inability of the raphanus radish and the brassica cabbage chromosomes to synapse with one another prevents the proper and appropriate chromosome pairing and results in a high degree of aneuploidy therefore the radish/cabbage hybrid is sterile, due to the high degree of aneuploidy that results from a cross bw two species that results in two sets of chromosomes that are the same in number, but that are not closely evolutionarily related and will not be able to synapse with one another when the cabbage/radish hybrid is attempting to produce viable gametes in the gametes that are created, there will be high degrees of aneuploidy making these gametes nonviable, and making the cabbage/radish individual sterile as it is not able to produce viable gametes among his strains of sterile alloploids such as the radish cabbage hybrid, Karpechenko discovered that on rare occasions a plant produced a viable seed, on rare occasions a plant produced a viable seed when these viable seeds that were produced by plants were planted and subjected to karyotyping, the plants were found to be allotetraploids with two sets of chromosomes from two different species, two sets of chromosomes each from two different species, totaling out to four sets of chromosomes in the plant producing these viable seeds among the strains of sterile alloploids that Karpechenko created, he discovered that on rare occasions a plant was not sterile and was able to produce a viable seed when these seeds were planted and then subjected to karyotyping, it was discovered that these plants were allotetraploids with two sets of chromosomes from each of the two species these plants were discovered to be allotetraploids with two sets of chromosomes from each species, this was discovered when these unusually viable seeds were planted and then subjected to karyotyping in the example given to us, the radish/cabbage allotetraploid contains 36 chromosomes rather than 18 chromosomes instead of being an allodiploid an organism produced from a cross of two different species and containing 1 set of chromosomes from each species, this radish/cabbage, the radish/cabbage hybrid is an allotetraploid, an organism still produced from two different species but containing 2 sets of chromosomes each from those two different species the homologous chromosomes from each of the two species are indeed able to synapse properly with one another the homologous chromosomes from each of the two species are indeed able to synapse properly with one another, because this is an allotetraploid organism, an organism resulting from a cross bw two species and containing 2 sets of chromosomes from each species, the homologous chromosomes, within these groupings of two sets of chromosomes are indeed able to synapse with one another because they are homologous and almost genetically identical to one another when anaphase of meiosis I occurs, the pair of synapsed chromosomes can disjoin equally in order to produce cells with 18 chromosomes each when anaphase of meiosis I occurs, the pair of synapsed chromosomes can disjoin equally in order to produce cells with 18 chromosomes each, cells contains a haploid set from the radish and a haploid set from the cabbage these cells will give rise to gametes with 18 chromosomes, containing a haploid set of radish chromosomes and a haploid set of cabbage chromosomes, gametes that can combine with other diploid gametes in order to produce an allotetraploid organism containing a total of 36 chromosomes, 4 sets of chromosomes total, 2 sets each from each distinct species due to each gamete containing a haploid set of radish chromosomes and a haploid set of cabbage chromosomes joining to create a diploid set of radish chromosomes, and a diploid set of cabbage chromosomes, creating a tetraploid organism with 4 sets of chromosomes, specifically an allotetraploid organism in this way, the allotetraploid is considered a fertile organism karpachenko's goal was to create a "vegetable for the masses" that would combine the nutritious roots of the radish with the flavorful leaves of the cabbage unfortunately the fertile allotetraploid that he created was composed of the roots of the cabbage and the leaves of the radish he showed that it is possible to artificially produce a new self perpetuating species of plant by creating an allotetraploid

lethal allele

an allele that when present in an allelic combination has the potential to cause the death of the organism with that particular allelic combination lethal alleles are usually inherited in a recessive manner, meaning you need two lethal alleles in an allelic combination in order for the lethal allele to express whatever phenotype will potentially cause death to the organism if the absence of a specific protein leads to a lethal phenotype (one that can cause the death of an organism) , then the gene that encodes the very necessary protein (whose absence can cause death) is considered an essential gene for survival according to research done, 1/3 of all genes are considered essential, meaning mutations of these genes or the absence of these genes can be fatal to organisms lethal alleles prevent cells from dividing (prevents the process of mitosis) and therefore, an organism (with its cells being unable to divide and propagate) will die at a very early age lethal alleles can also exert their effects and cause the death of an organism quite late in an organism's life, or express themselves when the organism ends up in a particular environment that triggers/influences the expression of this lethal allele an example of this is Huntington disease Huntington's is caused by a dominant allele (therefore if you are heterozygous for it, then you will have the condition) Huntington's is characterized by: - a progressive degeneration/breakdown of the nervous system - dementia - early death the age when the above symptoms appear in affected individuals is bw 30-50

environmental conditions and their influence on the outcome of traits, the phenotypic expressions of particular traits by genes

an example of the environmental effect on gene expression is the arctic fox, Alopex lagopus the Alopex lagopus goes through two color phases during the cold winter (temperatures are low), the arctic fox/alopex lagopus is primarily white (its fur presents as white) during the hot summer (temperatures are far higher) the arctic fox/alopex lagopus is primarily brown (its fur presents as brown) the way the arctic fox's fur presents is influenced by the environment that the arctic fox is in the above example showcasing alleles affecting fur color that are temperature sensitive (code for different phenotypic expressions based on temperature) are found among many species of mammals, so this is a commonality amongst mammals

why does aneuploidy commonly cause an abnormal phenotype?

aneuploidy usually causes an abnormal phenotype, aneuploidy in an organism usually results in an abnormal phenotype of that organism, aneuploidy usually results in that organism with aneuploidy presenting as phenotypically abnormal consider the relationship bw gene expression and chromosome number in a species that has 3 pairs of chromosomes lets consider the relationship bw gene expression and chromosome number within a species that has 3 pairs of chromosomes within this species that has 3 pairs of chromosomes lets consider the relationship bw gene expression and chromosome number the level of gene expression is influenced by the total number of genes per cell compared with a diploid cell, if there is a gene that is carried on three chromosomes, that is present in three copies due to three copies of the chromosome it is found on rather than simply being present in the requisite two copies on the two chromosomes of a chromosomal pair, then more of the gene product that this gene is coding for is made, due to the presence of an extra and potentially unnecessary copy of this gene, resulting in a total of 3 copies of this gene rather than the requisite 2, which results in typically more gene product being created due to an extra gene being expressed, one more than is required to be expressed an example of this is where a gene that is present in 3 copies on 3 copies of a particular chromosome rather than present in 2 copies on 2 copies of a particular chromosome in a pair, this gene that is present in 3 copies probably on 3 copies of the chromosome where it is designated, will probably end up producing 150% of the gene product due to the presence of a third copy of the gene that is not typically found in genotypical and phenotypically normal organisms alternately, there is another connection in the other direction bw gene expression and chromosome number if there is only one copy of a particular gene present on one particular chromosome, only one copy of a particular gene present on one copy of a particular chromosome rather than the usual and requisite two copies of a gene on two copies of a particular chromosomes, then there is usually less of the gene product made, due to the missing chromosome and subsequent missing and necessary copy of that gene there is less gene product made if there is one gene copy on one chromosome present rather than 2 gene copies on 2 chromosomes of a pair present, probably only 50 percent of the gene product will be produced therefore in trisomic and monosomic individuals, an imbalance occurs bw the level of gene expression that is occurring on the chromosomes found in pairs vs the level of gene expression occurring in the chromosomes that are not found in pairs that are found in extra copies, producing extra gene product, or less copies, producing reduced gene product THE DIFFERENCE IN GENE EXPRESSION IN EUPLOID AND ANEUPLOID may not seem particularly dramatic at first however, a eukaryotic chromosome carries hundreds or even thousands of different genes on it a eukaryotic chromosome, a single eukaryotic chromosome carries hundreds or even thousands of genes on it therefore, when an organism has aneuploidy and is trisomic 2n+1 having one extra copy of a particular chromosome, or monosomic 2n-1. having one less copy of a particular chromosome, there are MANY GENE PRODUCTS potentially extremely important gene products that occur in excessive or deficient amounts due to the presence of hundreds or even thousands of genes on that additional or deleted chromosome, and the addition or deletion of hundreds or even thousands of genes occurring with trisomy or monosomy resulting in genetic imbalance, and gene products of genes appearing in excessive or deficient amounts this imbalance among many genes, where either some genes are producing excess product to trisomy, or some genes are producing deficient and reduced product due to monosomy, and then other genes are producing normal amounts of gene product, there is a genetic imbalance here that is hard and rather impossible to correct, and this resulting genetic imbalance where with every gene there is not the automatic participation of 2 copies of that gene, this genetic imbalance seems to be the underlying issue of the abnormal phenotypic effects that occur due to aneuploidy in most cases these effects of aneuploidy are detrimental and produce an individual that is considerably less likely to survive than a euploid individual, with a total number of chromosomes that is a multiple of a typical set of chromosomes within its species

multiple alleles

as researches have looked at genes on the molecular level within natural populations of organisms, they understand the majority of genes exist in multiple alleles (more than two variants of a character) within a population, genes are usually found in 3 or more alleles (3 or more variants of a character) example of multiple alleles- coat color in rabbits C- full coat color cch- chinchilla pattern of coat color ch- himalayan pattern of coat color c- albino the gene coding for coat color codes for an enzyme called tyrosinase tyrosinase is the first enzyme within a metabolic pathway that leads to the creation of melanin from the amino acid tyrosine so you start with the amino acid tyrosine and through the metabolic pathway you end up with melanin, and tyrosine is the first enzyme within this metabolic pathway that creates melanin two forms of melanin result from this pathway Eumelanin- a black pigment- this eumelanin, a black pigment is the first melanin made by this metabolic pathway that begins with the enzyme tyrosine Phaeomelanin- an orange, yellow pigment- this phaeomelanin, an orange/yellow pigment is made from eumelanin- the black pigment created first by the metabolic pathway alleles from other genes coding for different things can possibly influence the relative amounts of emulation and phaeomelanin created as a result of this metabolic pathway the differences in the variety of alleles (the ones coding for a full coat color, chinchilla, Himalayan, and albino) is related to the function of the enzyme tyrosinase that is the first enzyme involved in a metabolic pathway that produces the melanin that you can see in the coat (that gives the coat its sheen and color) C allele- codes for a fully functional tyrosinase, this fully functional tyrosinase allows for the synthesis of both eumelanin- black pigment and phaeomelanin- orange/yellow pigment this results in the C allele ultimately coding for a fully brown coat color this allele is dominant over the chinchilla, Himalayan, and albino coat color cch allele- codes for a partially functional tyrosinase, codes for a partial defect in tyrosinase this leads to a slight reduction in eumelanin-black pigment and a dramatic, large reduction in phaeomelanin- orange/yellow pigment produced from eumelanin this makes the coat color gray ch allele- this allele ultimately codes for the phenotypic expression of a Himalayan pattern coat color this is a temperature sensitive allele this allele codes for a change in the structure of tyrsonase (so the enzyme doesn't have a partial defect as caused by the cch chinchilla allele or is wiped out as caused by the c albino allele, but rather has an alteration in its structure) this makes tyrosinase function enzymatically in that metabolic pathway only at low temperatures therefore tyrosinase, functioning in the metabolic pathway that produces eumelanin-black pigment and from that phaeomelanin- orange/yellow pigment, functions only in cooler areas of the body (areas of the body with lower temperatures) these cooler areas of the body include: - the tail - the paws - the tips of the nose and ears there are similar kinds of temperature-sensitive alleles found in other species of domestic animals an example is the Siamese cat coloration is different in different parts of the body due to an enzyme involved in a.metabolic pathway that produces melanin being functional at different temps, and therefore functional at different portions of the body with a particular temperature c allele- this allele codes for a complete loss of tyrosinase, tyrosinase as an enzyme is not present, and therefore the coat of the rabbit presents as white

Gregor Johann Mendel

born in 1822 known as the father of genetics precision and attention to detail are two characteristics he developed as a grafter he consistently crossed pea plants for 8. years, thousands of them he also kept very detailed and meticulous records of all of these crosses and their quantitative outcomes before Mendel specifically worked with pea plants, many plant breeders conducted experiments aimed at obtaining flowers w new varieties of colors, the objective was finding new colors, being able to produce pea plants with colors not previously seen

cell fusion techniques

cell fusion techniques can be utilized in order to make hybrid plants so far we have examined several mechanisms that produce variations in chromosome number, several methods that produce variations in chromosome number within an organism or its offspring some of these processes are processes and methods that occur naturally, and have been important factors in regards to speciation and evolution in addition to this, agricultural geneticists are able to administer treatments such as colchicine which interferes with the proper functioning of the spindle apparatus during anaphase the segregation of chromosomes by binding to tubulin, a protein that makes up the spindle apparatus and composes it, and can bring about nondisjunction perhaps even complete nondisjunction which promotes polyploidy, that allows these agricultural geneticists to obtain and acquire polyploid plants with desirable and advantageous traits more recently, researchers have been able to develop cellular approaches to produces hybrids more recently researchers have been able to develop cellular approaches in order to produce hybrids with altered chromosomal composition more recently researchers have been able to develop cellular approaches in order to produce hybrids with altered chromosome composition, altered chromosome numbers these cellular approaches have important applications in research and agriculture there is a technique known as cell fusion, where individual cells are mixed together and made to fuse with one another there is a technique known as cell fusion where individual cells are mixed together and made to fuse with one another in agriculture, cell fusion this technique of cell fusion where individual cells are mixed together and made to fuse with one another can produce new strains of plants an advantage of this approach of cell fusion that will cause individual cells to mix together and fuse, potentially producing new strains of plants is that researchers can artificially cross two species that are not able to interbreed naturally an example of these, crossing two species that are unable to interbreed naturally with one another there is the use of cell fusion in order to produce a hybrid gas the parents cells were derived from tall fescue grass also known as festuca arundinacea the parent cells were derived from tall fescue grass also known as festuca arundinacea and Italian ryegrass also known as lolium multiflorum, two different species of grass that were fused to produce a hybrid grass using the technique of cell fusion prior to fusion, the cells from these two individual species of grass, tall fescue grass and Italian ryegrass were treated with agents that gently digest the cel wall without rupturing the plasma membrane both species of grass were treating with agents that gently digested the cell wall without rupturing the plasma membrane of these parents cells derived from two different species of grass this process of treating the parent cells derived from two distinct species of grass with an agent that gently digested the cell walls of these cells but did not rupture the cell membrane occurred prior to fusion a plant cell without a wall is called a PROTOPLAST a plant cell without a wall is called a protoplast a plant cell without a wall is called a protoplast the protoplasts were mixed together with one another and then treated with agents that promote cellular fusion to occur these protoplasts, plant cells without cell walls but with unruptured plasma membranes were mixed together and treated with agents that promote fusion immediately after this takes place, the mixing together of the protoplasts also known as plant cells without cell walls and the introduction of agents that promote fusion, a cell containing two separate nuclei is formed this cell containing two separate nuclei is known as a heterokaryon the cell containing two separate nuclei is known as a heterokaryon the cell containing two separate nuclei results from the protoplasts being mixed together and treated with agents that promote cellular fusion this resulting cell is designated as a heterokaryon, containing two separate nuclei, and this heterokaryon spontaneously goes through a nuclear fusion process in order to produce a hybrid cell containing a single nucleus, a nucleus that is a combination of those two previously separate nuclei the allotetraploid that is shown in the figure has phenotypic characteristics that are intermediate bw the two species of gas, it has phenotypic characteristics that are intermediate bw the two species of grass, the tall fescue grass and the Italian ryegrass, an this is due to this allotetraploid plant developing from a hybrid cell formed from cellular fusion containing the genetic material of both tall fescue grass and the Italian ryegrass, resulting in an organism developed from that hybrid cells that contains a mixture of the genetic material found with tall fescue plants and Italian ryegrass plants, that has phenotypic characteristics that are intermediate bw the phenotypic characteristics of tall fescue grass and Italian ryegrass

X-linked muscular dystrophy in dogs

certain breeds of dogs have amongst them the disease X-linked muscular dystrophy- golden retrievers are a particular breed impacted by this condition the genetic mutation leading to the phenotypic expression of DMD occurs in the dystrophin gene, leading to the malfunctionality of this gene, and muscle weakness in all muscles but also particularly important muscles such as the heart and breeding muscles due to the dystrophin not functioning properly and anchoring the cytoskeleton to the plasma membrane, strengthening it the symptoms in golden retrievers include: -severe weakness -muscle atrophy both of these traits begin to show at 6o to 9 weeks of age most dogs that inherit this disorder pass away prior to becoming a year old however, some dogs are able to survive for 3-5 years and reproduce a cross bw an unaffected female dog with a homozygous dominant allelic combination (two copies of the wild type gene coding for properly functioning dystrophin) and an affected male dog with muscular dystrophy that carries the mutant allele in a homozygous recessive allelic combination and has survived to reproductive age when constructing a Punnett square for a x-linked trait, we need to consider the alleles on an X chromosome we also need to consider that males may transmit a Y chromosome that is not linked to this trait instead of an X chromosome that is

changes in euploid can occur by autopolploidy, alloploidy, and allopolyploidy

changes in euploidy can occur by autopolyploidy, alloploidy, and allopolyploidy different mechanisms account for changes in the number of chromosome sets among natural populations of plants and animals different mechanism account for changes in the number of chromosome sets among natural populations of plants and animals different mechanisms account for changes in the number of chromosome sets among natural populations of plants and animals as previously mentioned, complete nondisjunction, due to a general defect within the spindle apparatus, can produce an individual with one or more extra sets of chromosomes this organism, this individual with one or more extra sets of chromosomes is designated as an autopolyploid the prefix, auto means self, and the term polyploid means many sets of chromosomes, and refers to an increase in the number of chromosome sets within a single species an organism that has one or more extra sets of chromosomes is designated as an autopolyploid an organism that has one or more extra sets of chromosomes is designated as an autopolyploid an organism that has one or more extra sets of chromosomes is designated as an autopolyploid an organism that has one or more extra sets of chromosomes is designated as an autopolyploid the prefix of this terminology is auto, which means self the suffix of this terminology, polyploid means many sets of chromosomes the suffix of this terminology is polyploid meaning many sets of chromosomes autopolyploidy means self, many sets of chromosomes, and the term autpolyploidy refers to an increase in the number of chromosome sets within a single species autopolyploidy means self, many sets of chromosomes the term autopolyploidy refers to an increase in the number of chromosome sets within a single species, autopolyploidy refers to an increase in the number of chromosome sets within a single species autopolyploidy refers to an increase in the number of chromosome sets within a single species A MUCH MORE COMMON MECHANISM for change in chromosome number is designated as alloploidy a much more common mechanism for change in chromosome number is designated as alloploidy what exactly is alloploidy alloploidy is a result of interspecies crosses alloploidy is a result of interspecies crosses alloploidy is a result of interspecies crosses an alloploid that has one set of chromosomes from two different species is known as an allodiploid an alloploid, an organism resulting from an interspecies cross that has one set of chromosomes from two different species is known as an allodiploid, as this term denotes that this organism is the result of cross bw two different species, and it has two sets of chromosomes, 1 from each different species this event is most likely to occur bw species that are close evolutionary relatives this event of the creation of an alloploid is most likely to occur bw species that are closely evolutionarily related the creation of an alloploid is most likely to occur bw species that are closely evolutionarily related to one another, the creation of an alloploid is most likely to occur bw species that are closely evolutionarily related to one another for example, closely related species of grasses may interbreed in order to produce allodeploids closely related species of grasses may interbreed with one another in order to produce allodiploids closely related species of grasses may interbreed with one another in order to produce allodiploids, organisms that are the result of a cross bw two different species, and inherit one set of chromosomes from each different species AN ALLOPOLYPLOID contains two or mores sets of chromosomes from two or more species an allopolyploid contains two or more sets of chromosomes from two or more species in this case, the allotetraploid is an organism that is result of a cross bw two different species, where it has two complete sets of chromosomes from two different species, resulting in 4 sets of chromosomes total, designating it as a tetraploid containing 4 sets of chromosomes, containing 2 sets from each different species that crossed in order to produce this offspring so 2 sets each from 2 different species in nature, allotetraploids usually arise from allodiploids, organisms that result from a cross bw two different species, inheriting a single set of chromosomes from each species that contributed genetic material in order to produce this allodiploid this can occur when a somatic cell, a cell of the body within an allodiploid, containing two sets of chromosomes, one from each species, undergoes complete nondisjunction where all of the chromosomes transfer to a single daughter cell rather than splitting bw the two daughter cells, and an allotetraploid cell is created, containing 4 chromosome sets, 2 chromosome sets each from a different species, resulting from an allodiploid cell that underwent complete nondisjunction and resulted in four sets of chromosomes going to a single cell rather than being split in plants, such a cell can continue to grow, this allotetraploid cell that descended from an allodiploid cell can continue to grow and therefore produce a section of the plant that is allotetraploid this allotetraploid cell that descended from an allodiploid somatic cell can continue to grow and therefore produce a section of the plant that is allotetraploid if this part of the plant produced seeds by self pollination, the seeds would give rise to allotetraploid offspring if this part of the plant produced seeds by self pollination, the seeds would give rise to allotetraploid offspring cultivated wheat is a plant in which two species must have interbred in order to create an allotetraploid, and then a third species interbred with an allotetraploid in order to create an allohexaploid

condensin and cohesin and their different distinct roles in the structure of metaphase chromosomes

condensin and cohesin play different roles in regards to how they influence the structure of metaphase chromosomes they play different roles in how they influence the structure of metaphase chromosomes, and this difference in their responsibility and functionality is showcased in their names PRIOR TO MITOSIS, prior to the M phase (so potentially during interphase which is the precursor to the M phase), CONDENSIN IS FOUND OUTISIDE OF THE NUCLEUS recall that condensin is responsible for the compaction/condensation of chromosomes because condensin is responsible for the compaction/condensation of chromosomes, the compaction and condensation of the DNA composing chromosomes, it makes sense that this protein responsible for the compaction/condensation of chromosomes will not be found within the nucleus (the location of the cell's DNA) prior to mitosis, because prior to mitosis the DNA is in interphase, where it is replicated during the Synthesis S phase and needs to be decompacted and decondensed in order to be transcriptionally active for DNA replication the protein condensin is not required until the initiation of M phase, because during prophase and up until metaphase, the chromosomes under compaction/condensation to a compaction where a single chromosome has a diameter of 1400 nm this is where condensin is required in order to promote the compaction of the DNA, the compaction/condensation of the chromosomes that occurs during M phase, during prophase and metaphase AS M PHASE BEGINS CONDENSIN IS OBSERVED TO COAT THE INDIVIDUAL CHROMATIDS as the M phase begins, as the mitotic phase begins, condensin is observed to coat the individual sister chromatids that are joined with one another in order to form one individual chromosome composed of 2 sister chromatids joined at the centromere the condensin, which promotes the compaction/condensation of DNA coats the individual sister chromatids at the beginning of the M phase, where euchromatin, decompacted, decondensed, and transcriptionally active DNA is converted to heterochromatin, compacted, condensed, and transcriptionally inactive DNA what is the particular role of condensin in the process of DNA compaction/condensation that DNA promotes what is the particular role of condensin in the process of DNA compaction and condensation, the process of chromosomal compaction and condensation that it promotes what does condensin specifically due in order to promote the compaction and condensation of DNA it is not well understood what exactly is condenser's role in promoting the compaction and condensation of DNA CONDENSIN IS OFTEN IMPLICATED IN THE PROCESS OF CHROMOSOMAL CONDENSATION condensin is often indicated in the process of chromosomal condensation, condensin is often indicated in the process of chromosomal condensation and compaction, in previously implemented research that has been done, condensin has been indicated to play a not yet well understood role in the comapction and condensation of chromosomes and therefore the compaction and condensation of the DNA composing these chromosomes in previously implemented research, scientists have been able to deplete condensin, to mitigate the presence of condensin in cells going through the mitotic phase, in cells undergoing cellular division, and the chromosomes are still capable of compaction and condensation, suggesting that condensin, while it may promote chromosomal compaction and condensation, may not be required and necessary for the process of chromosomal compaction to occur HOWEVER THESE CONDENSED CHROMOSOMES these chromosomes that are condensed and compacted in the scientifically, experimentally implemented depletion of condnensin SHOW ABNORMALITIES in their ability to separate from one another during cell division these chromosomes that are compacted and condensed in the absence of condensin, the protein that is thought to promote the compaction and condensation of chromosomes, show abnormalities in their ability to properly separate from one another during the mitotic phase these results showcase THAT CONDENSIN IS INDEED IMPORTANT IN THE PROPER ORGANIZATION OF HIGHLY CONDENSED CHROMOSOMES condensin has been determined to be v important in regards to the proper organization of highly condensed chromosomes, in regards to the proper organization of highly condensed chromosomes such as metaphase chromosomes what is the function of cohesin? the function of cohesin is to promote the BINDING THE COHESION BW SISTER CHROMATIDS the function of cohesin is to promote the binding that occurs between the sister chromatids as 2 of them, joined initially at solely the centromere, combine to form an individual single chromosome the function of cohesin is to promote the binding bw sister chromatids forming single chromosome, to promote the alignment of sister chromatids, to promote the cohesion bw sister chromatids that join together in order to form a single chromosomal entity after S phase, and through to the middle of prophase, the SISTER CHROMATIDS REMAIN ATTACHED TO ONE ANOTHER ALONG THEIR RESPECTIVE LENGTHS after the occurrence of S phase, where all of the DNA is replicated, and through to the midst of prophase, the sister chromatids remain attached along their lengths to one another as they form an individual chromosome, this is promoted by cohesin THIS ATTACHMENT this alignment of the sister chromatids along their respective lengths as they join to create a single individual chromosome that occurs after the S phase, when all of the DNA and chromosomes are replicated, through to the middle of prophase, is promoted and maintained by cohesin that promotes and maintains the cohesion bw sister chromatids cohesin which promotes the cohesion and alignment of sister chromatids with one another as 2 of them form an individual chromosome, is found along the entire lengths of these sister chromatids, that are aligned and joined together along their entire lengths in particular species, such as mammals, COHESINS that are located along the chromosomes arms, cohesins that are located along the lengths of sister chromatids that join together in order to form individual chromosomes, ARE RELEASED DURING PROPHASE the release of cohesin during prophase that occurs within some mammals causes the sister chromatids that were previously aligned and attached to one another due to the presence of cohesin along their lengths to be able to separate from one another after the release of cohesin during prophase that occurs in some mammals HOWEVER there is some cohesin that remains attached to the lengths of the sister chromatids, particularly at the centromeric regions, which designates the centromere as the sole point of contact bw sister chromatids that allows them to form individual chromosomes the centromere then serves as the main linkage bw two sister chromatids, after the release of cohesin during prophase that occurs for some mammals, where the cohesin is released along the majority of the lengths of the pairs of sister chromatids, allowing them to separated, but some cohesin remains concentrated at the centromeric regions connected the two sister chromatids, maintaining this connection during anaphase, which is when these two sister chromatids separate at this linkage point as well DURING ANAPHASE the cohesins that remained bound to the centromere, causing there to be a main linkage point still occurring bw the two sister chromatids composing a pair that constitutes a chromosome ARE DEGRADED BY A PROTEASE DESIGNATED AS SEPARASE this allows full sister chromatid separation to occur

Creighton and McClintock

creighton and mcclintock creighton and mcclintock showed that crossing over produced new combinations of alleles and resulting in the exchange of segments bw homologous chromosomes creighton and mcclintock showed that crossing over produced new combinations of alleles and that crossing over bw chromosomes and therefore genes resulted in the exchange of segments bw homologous chromosomes as we have seen, Morgan's studies were consisted with the hypothesis that crossing over occurs bw homologous chromosomes in order to produce new combinations of alleles as we have seen the studies implemented by Morgan, and the studies implemented by Morgan were consistent with the hypothesis that crossing over, the phenomenon of crossing over and rearrangement of genetic material occurs bw homologous chromosomes in order to produce new combinations of alleles the studies implemented by Morgan were consistent with the hypothesis that crossing over occurs bw homologous chromosomes in order to produce new combinations of alleles to obtain direct evidence that crossing over can indeed result in genetic recombination, Harriet Creighton and Barbara McClintock used an interesting strategy involving parallel observations to obtain direct evidence that crossing over can indeed result in genetic recombination, Harriet Creighton and Barbara McClintock utilized an interesting strategy involving parallel observations in order to obtain direct evidence that crossing over can indeed result in the occurrence of genetic recombination, Harriet Creighton and Barbara McClintock used an interesting strategy involving parallel observations in studies that were conducted in 1931, they first made crosses that involved two linked genes in order to produce parental and recombinant offspring in studies that were conducted in 1931, Harriet Creighton and Barbara McClintock used an interesting strategy involving parallel observations in order to determine that crossing over can result in genetic recombination these two individuals first made crosses that involved two linked genes influenced by the phenomenon of genetic influence in order to determine that crossing over can result in genetic recombination these two individuals first made crosses involving two linked genes in order to produce parental and recombinant offspring second they utilized a microscope to view the structures of the chromosomes in both the parents and the offspring (the parental and nonparental offspring alike) because the parental chromosomes had some unusual structural features, they could microscopically, these scientists were able to microscopically distinguish the two homologous chromosomes within a pair because the parental chromosomes and some unusual structural features, they could microscopically distinguish bw the two homologous chromosomes present within a pair, due to these parental chromosomes having some unusual structural features as we Weill see, this ability to distinguish bw the two homologous chromosomes of a pair enabled them to correlate the occurrence of recombinant and non parental offspring with microscopically observable exchanges in the segments of homologous chromosomes the scientists due to them being capable of distinguishing bw the two homologous chromosomes of a pair due to their being microscopically distinguishable and distinct characteristics on the parental chromosomes were thus able to correlate the occurrence of nonparental and recombinant offspring with observed microscopic changes within the structures of homologous chromosomes Creighton and McClintock focused much of their attention on the pattern of inheritance traits in corn in particular Creighton and Mcclintock focused much of their attention on the pattern of inheritance of traits of corn in particular the particular corn species that these two scientists focused on, the particular corn species that these two scientists focused on, has 10 different types of chromosomes per set of chromosomes, and these 10 different types of chromosomes within a set are identified as chromosome 1, chromosome 2, chromosome 3, and so on and so forht in previously implemented cytological examinations of the chromosomes within this particular species of corn, there were some strains that were found to have an unusual chromosome 9 with a dark staining knob at one end of this chromosome 9 in the cytological examinations implemented on this particular species of corn, there were several strains of this corn that were found to have an unusual chromosome 9 with a darkly staining knob at one end in addition to this, the unusual chromosome 9 with a darkly staining knob at one end of the chromosome, McClintock identified an abnormal version of chromosome 9 that also had one extra piece of chromosome 8 attached at the other end McClintock also identified an abnormal version of chromosome 9 that also had one extra piece of chromosome 8 attached at the other end in addition to finding the unusual chromosome 9 in some strains of corn with a darkly staining knob found at one end, McClintock identified an abnormal version of chromosome 9 that in addition to the darkly staining knob at one end of chromosome 9, also had an extra piece of chromosome 8 on the other end of chromosome 9 this chromosomal rearrangement is known as a translocation this chromosomal rearrangement is known as a translocation this chromosomal rearrangement is known as a tranlocation this chromosomal rearrangement is known as a translocation, the extra piece of chromosome 8 attached to the other end of the abnormal chromosome 9, which on the opposing end had a darkly staining knob the two scientists creighton and mcclintock insightful realized that this abnormal chromosome 9 could be used in order to determine if the two homologous chromosomes physically exchange segments as a result of crossing over the two scientists insightfully realized that this abnormal chromosome 9 could be used in order to determine if the two homologous chromosomes physically exchange segments as a result of crossing over or do not the two scientists knew that a gene was located near the knobbed end of chromosome 9 the two scientists knew that a gene was located near the knobbed end of chromosome 9 the two scientists knew that a gene was locate near the knobbed end of chromosome 9, and this gene near the knobbed end of chromosome 9 provided color to corn kernels this gene that was found near the knobbed end of chromosome 9 provided color to the corn kernels this gene that was found near the knobbed end of chromosome 9 provided color to the corn kernels, and was found in the form of two alleles this gene that was found near the knobbed end of chromosome 9 and provided color to the corn kernels existed in two alleles the two alleles that this gene coding for corn kernel color existed in were: the dominant C allele (colored) the recessive allele c (colorless) there was a second gene in addition to this first one coding for the corn kernel color this second gene was located near the chromosomal piece/segment of chromosome 8 that was located at the other end of the abnormal chromosome 9 this second gene was located near the translocated piece/segment of chromosome 9 that was located on the other end of chromosome 9, opposite of the knob located on the other end where nearby there was that first gene with two alleles, C (colored) and c (colorless) coding for the color of the corn's kernels the second gene was located near the translocated piece of chromosome 8 on the other end of chromosome 9 and this second gene affected the texture of the kernel endosperm there were two alleles/two allelic combinations for this particular second gene affecting the texture of kernel endosperm the first allele was the dominant allele denoted as Wx, and this dominant allele caused starchy endosperm the second allele was denoted as wx, and this caused waxy endosperm Creighton and McClintock both reasoned that a crossover involving a normal chromosome 9 and a knobbed/translocated chromosome 9 would produce a chromosome that either had a knob or translocation from chromosome 8, but not both, and this would prove that crossing over involves the physical exchange of chromosomal segments amongst homologous chromosomes these two types of chromosomes resulting from a crossover bw a normal chromosome 9 and an abnormal chromosome 9 with a knobbed end with a predilection for staining and a translocated piece of chromosome 8 would result in two new chromosomes, either having the knob or the translocation, but not both, and both of them being nonparental and recombinant, not matching either of the parental chromosomes, these two chromosomes resulting from a crossover would be markedly and distinctly different from either of the parental chromosomes they carried out an experiment, Creighton and McClintock Creighton and McClintock began with a corn strain the two scientists began with a corn strain that carried an abnormal chromosome with a knob at one end and a translocation from chromosome 8 at the other end genotypically, this chromosome with a knob at one end, and a translocated segment of chromosome 8 at the other end, was identified as Cwx, meaning that this chromosome was coding for colored corn kernels and waxy kernel endosperm the cytologically normal chromosome 9 in this strain was genotypical cWx, coding for colorless corn kernels and starchy kernel endosperm this corn plant, termed parent A, had the genotype Cc Wxwx this corn plant, termed parent A, had the genotype CcWxwx due to the presence of the abnormal chromosome 9 and the normal chromosome 9 within its genotype, and that meant it was heterozygous dominant for two genes, and was coding for colored corn kernels and starchy kernel endosperm this above corn plant, termed parent A, was crossed with another corn plant designated as parent B, and this corn plant designated as parent B carried two cytologically normal chromosomes, two cytologically normal chromosome 9s, therefore having the genotype of ccWxwx, a homozygous recessive allelic combination for the gene coding for corn kernel color, resulting in the genotype of this corn plant coding for colorless corn kernels, and a heterozygous dominant allelic combination for the gene coding for kernel endosperm texture, resulting in the genotype of parent B coding for starchy kernel endosperm the scientists then observed the kernels in two ways first they analyzed and examined the phenotypes of the kernels in order to see if these kernels were: colored or colorless and starchy or waxy second, the chromosomes in each of the kernels were examined under the microscope in order to determine their cytological appearance a total of 25 kernels were observed what was the hypothesis of this experiment? offspring with non parental phenotypes are the product of a crossover offspring with non parental phenotypes are the product of a crossover occurring bw two chromosomes offspring with non parental phenotypes are the product of a crossover occurring bw a pair of homologous chromosomes, or multiple pairs of homologous chromosomes this crossover occurring where Parent A and Parent B are crossed with one another should produce non parental chromosomes via an exchange of chromosomal segments bw the homologous chromosome of parent A and parent B, bw the homologous chromosome pairs of A and B testing the hypothesis there are the starting materials two different strains of corn there are the starting materials, two different strains of corn one strain is referred to as parent A one strain is referred to as parent A, and this strain of Parent A had an abnormal chromosome one strain is referred to as parent A, and this strain of Parent A had an abnormal chromosome 9 one strain is referred to as parent A, and this strain of Parent A had an abnormal chromosome 9 (knobbed/translocated) one strain is referred to as parent A, and this strain of Parent A had an abnormal chromosome 9 (knobbed/translocated chromosome 9) with a dominant C allele and a recessive wx allele it also had a cytologically normal copy of chromosome 9 that carried the recessive c allele and the dominant Wx allele, so it had chromosome 9s with opposite allelic combinations the genotype for this parent A was therefore CcWxwx the other strain, referred to as parent B had two normal versions of chromosome 9, the. chromosomes having the genotypic allelic combination of cWx and cwx, therefore resulting in the parent B strain having the allelic combination ccWxwx crossing the two strains with one another the tassel is the pollen bearing structure

crossing over may produce

crossing over may produce recombinant phenotypes crossing over may produce recombinant phenotypes crossing over may produce recombinant phenotypes crossing over may produce recombinant phenotypes even though the allies for different genes may be linked along the same chromosome the linkage of these genes, the locations of these genes and how they may be linked along the same chromosome can be changed through the implementation of meiosis so even though two genes and the alleles of the genes may be linked to one another, may be physically linked to one another along the same chromosome, this linkage, this physical linkage to one another due to these two genes and therefore their alleles being located on the same chromosome can be changed through the implementation and completion of meiosis, through the process of crossing over that occurs during the meiotic process in diploid eukaryotic species, homologous chromosomes, chromosomes that are almost genetically identical (they are the same size, have the same centromere location, the same banding patterns, indicating that they encode all of the same genes, the only difference will be in the alleles of these genes, because that is where they will differ, in the alleles of these genes) within diploid eukaryotic species, homologous chromosomes, chromosomes that are almost genetically identical to one another are able to exchange pieces, chromosomal segments with one another this phenomenon of homologous chromosomes being able to exchange pieces and chromosomal segments with one another is designated as crossing over this event of crossing over where homologous chromosomes are able to exchange pieces and chromosomal segments with one another is designated as the process of crossing over, and occurs during prophase I of meiosis I as discussed in chapter 3, the replicated chromosomes, that are known an designated as sister chromatids, associated with the homologous sister chromatids in order to form a structure known and recognized as a bivalent as discussed in chapter three, the replication chromosomes that are designated as sister chromatids, align themselves with their homologous sister chromatids during prophase I of meiosis I and then crossover with one another two pairs of sister chromatids, one replicated and one original, align with one another in order to form a structure designated as a bivalent, so they can cross over with one another a bivalent is a structure that is composed of two pairs of sister chromatids in prophase I of meiosis I it is common for a sister chromatid of one pair to cross over with the sister chromatid of another pair, a sister chromatid from the other pair that is assisting in forming the structure of the bivalent there is a figure that considers meiosis when here are two genes that are linked on the same chromosome there is a figure that considers meiosis when there are two genes that are linked on the same chromosome, that are physically linked to one another by being located on the same chromosome one of the parental chromosomes carries the A and B alleles, while the homolog carries the a and b alleles so one of the parental chromosomes carries the dominant A and B alleles, while the homologous chromosome carries the recessive a and b alleles in the figure shown, no crossing over bw these homologous chromosome has occurred, therefore the resulting haploid cells contain the same combination of alleles that the original chromosomes contained themselves, due to the phenomenon of crossing over not occurring the resulting haploid cells due to the process of crossing over not actually occurring, will consist of the same allelic combinations as the original chromosome and its homolog, as no crossing over bw these two chromosomes occurred in this case, there will be two haploid cells that are carrying the dominant A and B alleles, mimicking the original parental chromosome that had this allelic pairing of dominant A and B alleles, and there are two haploid cells that are carrying the recessive a and b alleles, mimicking the original homologous chromosome of the parent chromosome that contained the allelic pairing of the recessive a and b alleles there is a contrast to the first figure, where crossing over does indeed occur when crossing over does occur bw the parental chromosome containing the allelic pairing A and B, the two dominant alleles for their respective genes, and the homologous chromosome containing the allelic pairing of a and b, the two recessive alleles for those same respective genes, different haploid cells from the meiotic process result in this case, two of the resulting haploid cells contain combination s of alleles, namely A and b or a and B, which differ from the allelic combinations found on the original chromosomes, these allelic combinations of A and b or a and B, mixing the dominant and recessive alleles, is markedly different from either of the allelic pairings that the original chromosome and its homologous chromosome had, where the dominant alleles and recessive alleles were kept apart from one another and respectively together in a pairing in these two haploid cells with either the A and b or a and B pairing of alleles for their respective genes, the grouping of linked alleles has changed in these two haploid cells the grouping of linked alleles has changed an event such as this, that leads to new combinations of alleles that were not seen in the original parent chromosome or its homologous chromosome, this phenomenon is known as genetic recombination the haploid cells carrying the A and b, or the a and B allelic combination, these allelic pairings that are markedly different from the allelic pairings of the parent chromosome or its homologous chromosome are designated as non parental cells or recombinant cells these haploid cells with these never before seen allelic pairing of A and b or a and B, are known as non parental cells or recombinant cells, because the allelic pairings that they do have come from the process of genetic recombination being implemented during the meiosis I and II that created these gametes, and the allelic combinations that these two haploid cells have are markedly different from the allelic combinations the allelic pairings of the parental cell, within the parental chromosome and its homologous chromosome likewise, if these haploid cells were gametes that participated in the process of fertilization, joining together with another gamete in order to form a zygote, the resulting offspring (due to the recombinant/nonparental gamete being a participation in the creation of the zygote resulting in this offspring) will also be known as nonparental offspring or recombinant offspring, as the allelic combinations of these offspring, the allelic pairings of these offspring will not match the allelic pairings within the parents' genomes, will not match the allelic pairings of their parent chromosomes and the homologous chromosomes to these parent chromosomes, due to the process of genetic recombination occurring in the formation of gametes through meiosis and causing new allelic pairings that were markedly different from those seen and identified in the parental chromosome and its homologous chromosome these offspring can display combinations of traits that are markedly different from the combinations of traits displayed by either parent in contrast to this, offspring that have inherited the same combination of alleles, the same allelic pairing that ar e found in the chromosomes of their parents, in either their parents chromosomes, the homologous chromosomes of those parental chromosomes, or both, the offspring that contain allelic combinations and pairings found in one or both of the parents are considered parental, or nonrecombinant offspring

allele

different versions of the same gene, half of an allelic combination

dosage compensation mechanisms

dosage compensation mechanisms within placental mammals: the sex chromosomes of placental mammals are: xx for females xy for males one of the X chromosomes in all of the somatic cells of females are inactivated (there is a Barr body x chromosome in every single somatic cell of placental mammal females) in particular species, the paternal X chromosome (the X chromosome inherited from the father of the organism) is inactivated in other species, (an example being the human species) the maternal or paternal X chromosome is the one that is inactivated (the one that becomes the Barr body is either the X chromosome inherited from the mother or the X chromosome inherited from the father), one of these X chromosomes (either the one inherited from the mother or father) is inactivated throughout the somatic cells of placental mammal females marsupial mammals xx for females xy for males the paternally derived X chromosome (the X chromosome inherited from the father) is the one that is inactivated within the somatic cells of females (this is the chromosome that becomes a Barr body, the X chromosome inherited from the father of the individual Drosophila melanogaster xx for females xy of males the level of expression of the genes located on the lone x chromosome found in males is increased two fold, so the gene expression of all the genes found on the X chromosome (of which Drosophila melanogaster males have one) is doubled in order to compensate for the lack of an x chromosome with an identical set of genes Caenorhabditis elegans xx for hermaphrodites x0 for males the level of expression of genes on both of the X chromosomes possessed in the allelic combination of hermaphrodites is decreased to 50% levels, that is more comparable to the gene expression of genes on the X chromosome occurring in males (as they only have one X chromosome)

X inactivation

during the process of the inactivation of an X chromosome, the chromosomal DNA becomes highly compacted and condensed within this X chromosome (The chromosomal DNA that composes the X chromosome is highly condensed and compacted) therefore many of the genes (that are encoded by this chromosomal DNA that has been highly compacted and condensed) are no longer active, and can no longer be expressed and have the phenotypic trait they code for be expressed when cell division of a cell with this inactivated X chromosome occurs, the resulting cell has this same X chromosome inactivated, due to the step prior to mitosis where all the DNA is replicated (where the inactive chromosome and its inactivated DNA encoding therefore inactivated genes are replicated in order to be passed on to the daughter cell) therefore all of the daughter cells, upcoming generations of somatic cells that will all stem from this original cell with an inactivated X chromosome will all have the same X chromosome (the maternally or paternally inherited one that was inactive in the origin cell) inactive in themselves therefore within all the somatic cells in the body stemming from the origin cell, there will be an X chromosome that has been inactivated, and is a Barr body, and this X chromosome that is inactivated will be the same one inactivated in the first if there is the presence of two different embryonic cells, each one with a differently inherited X chromosome that becomes inactivated, then there will be two sets of somatic cells in the body: one set with the maternally inherited X chromosome inactivated one set with the paternally inherited chromosome inactivated this can cause a difference in phenotype expression depending on which chromosome in a cell with which alleles for genes is active

epistasis specific definition

epistasis is a phenomenon where the alleles of one gene coding for a variant of a character mask the phenotypic expression of the alleles of another gene coding for another variant of the same character epistasis is considered relative to another phenotype the phenotype that researchers/geneticists establishes as their reference phenotype is usually the wild-type one in the above case, the reference phenotype is the purple flowered sweet pea plant, which is also the wild-type, more common one in this species homozygosity for the white allele of one gene (stemming from the allelic combination cc or pp) is able to mask the alleles of the other gene and the phenotypic expression of purple flowers that they are coding for THE cc GENOTYPE IS EPISTATIC TO PP or Pp THE pp GENOTYPE IS EPISTATIC TO CC or Cc both the allelic combination cc and pp are epistatic to the purple phenotype, any alleles coding for the purple phenotype the above example is one of recessive epistasis in which a recessive allelic combination can combat dominant alleles present and ensure that the phenotypic trait the recessive allelic combination is coding for is expressed the above epistatic interaction produces a ratio of two phenotypes, purple and white in a 9:7 ratio why does epistasis occur? it occurs due to the participation of two or more proteins in a common function an example of this is that there may be two proteins that are both participants in an enzymatic pathway that forms a product, they both play roles in this pathway, and therefore both plays roles in producing the product of this pathway specifically, analysis of the purple pigment in the sweet pea there is a colorless precursor molecule this colorless precursor molecule must be acted upon by two individual enzymes in order to produce the purple pigment that causes sweet pea flowers to be purple Gene C codes for a functional protein- enzyme C, which is one of the enzymes that act upon the colorless precursor in order to contribute to the production of the purple pigment Gene P codes for a different functional protein- Enzyme P, which is the other enzyme that acts upon the colorless precursor in order to contribute to the formation of purple pigment the lowercase c allele (2 copies of it in an allelic combination), result in a lack of production of enzyme C, meaning that the colorless precursor will not be acted upon this enzyme due to it not being synthesized, and therefore (since it needs to be acted upon by both enzymes in order to produce purple pigment) the purple pigment will not be produced the lowercase p allele (2 copies of it in an allelic combination) encodes a defective enzyme P, and the defectiveness of this enzyme means that the colorless precursor will not be acted upon by enzyme p, and therefore (since it needs to be acted upon by enzyme C and P in order to produce purple pigment) purple pigment will not be produce so if either allelic combination is present, cc or pp, one of the necessary enzymes required to act upon the colorless precursor so it can produce purple pigment will not be synthesized or will be defective, and no purple pigment will be made (the flowers remain white)

eukaryotes

eukaryotes, why are they designated as such? eukaryotes are designated as such bc this term comes from the Greek, eukaryote means TRUE NUCLEUS eukaryotes include: SIMPLE SPECIES INCLUDING SINGLE CELLED PROTISTS AND FUNGI single celled protists and fungi fall under the category of eukaryotes, an example of fungi is yeast, yeast falls under the category of eukaryote EUKARYOTES ALSO INCLUDE: more complex multicellular species, including: PLANTS ANIMALS AND OTHER FUNGI (fungi in addition to yeast) what makes eukaryotic cells distinctly different and demarcated from prokaryotic cells? eukaryotic cells contain organelles, also known as INTERNAL MEMBRANES ENCLOSING HIGHLY SPECIALIZED COMPARTMENTS the highly specialized compartments are the organelles, and highly specialized means they have v particular functions that they implement for the cell to function overall, and these organelles are enclosed by internal membranes and are thus considered individual entities floating within the eukaryotic cell, ultimately enclosed by the plasma membrane of the cell as a whole these compartments with their individual membranes form ORGANELLES organelles have specific functions an example of an organelle with a specific function: LYSOSOMES: lysosomes are responsible for the degradation of macromolecules, it digests macromolecules for the cell, either macromolecules that the cell no longer needs or macromolecules that the cell simply needs to be broken down into smaller monomers to be used for other functions ENDOPLASMIC RETICULUM AND Golgi body- the endoplasmic reticulum is responsible for protein modification, the Golgi body is responsible for also modifying these proteins and shipping them NUCLEUS the nucleus is another organelle, located at the center of the cell, the nucleus is surrounded and enclosed by TWO MEMBRANES these two membranes together compose the nuclear envelope that encloses the nucleus and the genetic information that the nucleus contains the majority of genetic material that one can find within chromosomes are found within the nucleus, located on the chromosomes found within the nucleus there are also particular organelles within EUKARYOTIC CELLS that contain smaller genomes, tiny sets of their own genetic materials the organelles that contain their own entities of genetic material include: mitochondria chloroplasts THE MITOCHONDRION has its own miniature genome and its function is to synthesize energy in the form of ATP THE CHLOROPLAST also has its own miniature genome and its function is to implement the process of photosynthesis and convert light energy into the chemical energy of food THE DNA that we find within these organelles, the mitochondria and the chloroplasts are designated as extranuclear DNA, bc they are found outside of the nucleus, IT IS CALLED EXTRANUCLEAR OR EXTRACHROMOSOMAL DNA in order to distinguish this DNA found in organelles besides the nucleus from the DNA found within that very organelle within eukaryotes, their DNA is found within linear chromosomes

heredity

factors that govern traits- genes, these are passed from parents to offspring throughout generations as discrete units

holandric genes

genes that are located on the Y chromosome an example of a holandric gene is the Sry gene found in mammals the expression of the Sry gene is necessary for male development to occur A Y-linked inheritance pattern is also quite distinctive, as the gene can only be passed from father to sons with the Y chromosome that only fathers are able to contribute exclusively to their sons

genetic imprinting at the cellular level

genetic imprinting, at the cellular level is an epigenetic process there are three stages to this epigenetic process known as 1) the establishment of the imprint during gametogenesis, the establishment of which inherited allele is imprinted and marked 2) the maintenance of this imprint during the process of embryogenesis, the creation of the zygote and within the adult somatic cells that develop from this zygote 3) the erasure and reestablishment of the imprint and the marked allele within the germ cells of organisms looking at genetic imprinting at the cellular level within mice and specifically looking at the inheritance patterns of the Igf2 gene we are looking at two heterozygous mice that have the maternally inherited recessive allele, Igf2- coding for a dwarf size, and the paternally inherited dominant, normal, wild type allele, Igf2, coding for the normal size due to the presence and implemented process of genetic imprinting, both of the mice only express the maternally inherited, dominant, normal, wild-type Igf2 allele within all of their somatic cells, and the pattern of this allele being the sole allele transcribed (the paternally inherited allele of Igf2 being the only one transcribed and expressed to code for normal size) is maintained through the proliferation of all the mice's somatic cells in the germ cells/haploid gametes of these organisms, the imprint of the paternally inherited allele being the only one expressed is erased, and the imprinting will be reestablished based on the sex of the animal and therefore the particular gametes it is producing : the female on the left, as she is female, and imprinting selects for the paternal allele, will only be able to pass on a silent, transcriptionally inactive (not transcribed) allele to all of her offspring, so her allele within her gametes will never be genetic determinants for the phenotype of the offspring the male on the right, as he is male, and the allele selected for is the paternal one in this particular case of genetic imprinting, all of the alleles within this organism's gametes will be transcriptionally active, and therefore will be passed on to the offspring and be the only allele expressed in the offspring's allelic combinations, therefore occupying the role as sole genetic determinant for the phenotypic expression of the offspring however, within the male mouse we are looking at, due to it being heterozygous, and having a dominant, normal, wild type Igf2 allele coding for normal size, as well as a recessive loss of function Igf2- allele coding for dwarf size, within its gametes, it will have gametes containing the normal, dominant, wild type Igf2 allele as well as gametes contained the recessive, loss of function Igf2- allele therefore if one of this male's offspring is formed from a gamete contained the Igf2- allele, then this particular allele can be transcribed into mRNA (it is transcriptionally active due to it being paternally inherited) and as it is a loss of function allele, it will not be able to produce the properly functioning Igf2 protein that will result in normal size (due to the fact that once again, this allele is a loss of function allele, and designated as such due to a deleterious mutation) therefore the offspring through the expression of their paternally inherited Igf2- allele, will express the dwarf phenotype genetic imprinting is permanent within the somatic cells of an organism, all of the cells that develop from the created zygote and the inherited allele that is marked for expression however, the marking of the allele to be expressed, transcriptionally active in the offspring, can change from generation to generation for example, within the female, she has the recessive, loss of function allele Igf2- in her allelic combination; she is actually homozygous for it within all of her somatic cells, the Igf2- allele is transcriptionally active and expressed however, due to the fact that she is female and the inheritance pattern here selects the paternally inherited allele to be the sole determinant of an offspring's phenotype, all of her gametes will contain an Igf2- allele (due to her being homozygous Igf2-) but will not be imprinted, and will therefore be transcriptionally inactive

genomic imprinting and x inactivation relationship

genomic imprinting can apparently have a role in and an influence on X inactivation genetic imprinting apparently specifically, within particular species, will play a role in selecting and marking the X chromosome for being transcriptionally inactive, not expressed, and from there, compacted and condensed into a Barr body an example of genomic imprinting and its relationship to x inactivation is that in marsupials: the paternally inherited X chromosome is the chromosome that is always marked to be transcriptionally inactive and therefore not expressed and turned into a Barr body in all of the somatic cells of the female offspring with 2 X chromosomes in their allelic combination therefore, X inactivation within marsupials is not random x inactivation within somatic cells due to the implemented process of genomic imprinting; it is always the maternal X chromosome that remains activated in all of the somatic cells of the female offspring, and always the paternally inherited X chromosome that remains inactivated and presents as a Barr body in all of the somatic cells of the female offspring x inactivation is determined and maintained within marsupials and is never random, due to the implementation of gene imprinting which selects which sex chromosome inherited from which parent is inactivated in all of the somatic cells of the offspring, and which sex chromosome inherited from which parent remains activated, expressed, and not compacted within all the somatic cells of the offspring

Joseph Kölreuter

he is a scientist that carried out the first systematic (outlined, planned, and implemented) studies of genetic crosses he carried out these systematic studies from 1761-1766 he crossed different strains of tobacco plants he found that offspring were oftentimes intermediate in regards to their morphological appearance, intermediate bw their parents physicalities he therefore believed due to the morphological appearance of the tobacco plant offspring that the parents of the offspring make equal genetic contributions to the offspring

Mendel experimentation with differing traits

he wanted to analyze characteristics that were markedly different amongst various true breeding lines the seven characters he analyzed: -height (tall or dwarf) -flower color (purple or white) -flower position (axial or terminal) -seed color (yellow or green) -seed shape (round or wrinkled) -pod color (green or yellow) -pod shape (smooth or constricted) all of the above traits (characters) were found in two variants Mendel wanted to cross different variants with one another

Mendel experimentation with pea strains

he wanted to determine if the characteristics of these peas bred true bred true- that means that this trait did not vary in appearance morphologically as he moved from generation to generation an example of this true breeding- there would be a pea plant with yellow seeds, and the next generation would also have yellow seeds if the plant self-fertilized, the offspring would still have yellow seeds

interphase chromosome compaction

how does the compaction level of interphase chromosomes vary? how does the compaction level of chromosomes within interphase vary? this variability amongst chromosomes within cells undergoing interphase can be studied and documented with the utilization of a light microscope the variability amongst chromosomes within cells undergoing interphase was initially observed, first observed by the GERMAN CYTOLOGIST EMIL HEITZ in 1928 Emil Heitz in 1928 was a German cytologist, and the first individual to observe the variability in chromosomes within cells undergoing interphase HETEROCHROMATIN this was a term coined by Emil hertz, heterochromatin DESCRIBES THE TIGHTLY COMPACTED REGIONS OF CHROMOSOMES heterochromatin describes the tightly compacted regions of chromosomes the tightly compacted regions of chromosomes are designated as heterochromatin, a term coined by Emil Heitz for the tightly compacted and condensed regions of chromosomes these regions of the chromosome, the heterochromatic and therefore highly condensed and compacted regions of chromosomes are usually TRANSCRIPTIONALLY INACTIVE they are usually unable to be transcribed these heterochromatic regions of chromosomes, because they are too dense and compacted to be unwound enough for transcription to properly occur EUCHROMATIN these are the less condensed and less compacted regions of chromosomes euchromatin refers to the less condensed, less compacted regions of chromosomes, the regions of chromosomes that are more unwound these areas of chromosomes, the euchromatic regions of chromosomes, are more definitively transcriptionally active, and these regions are capable of gene transcription gene transcription will occur at these sites, where there are euchromatic regions chromosomes in EUCHROMATIN, the 30 NM FIBER FORMS RADIAL LOOP DOMAINS in HETEROCHROMATIN, THESE RADIAL LOOP DOMAINS FORMED BY THE 30 NM FIBERS ARE FURTHER COMPACTED what is the distribution of euchromatin and heterochromatin in a typical eukaryotic chromosome during interphase? during interphase, what is the distribution of euchromatin and heterochromatin? what are the proportions of euchromatin and heterochromatin that are occurring in a typical eukaryotic chromosome in a cell undergoing interphase? the eukaryotic chromosome in a eukaryotic cell undergoing interphase CONTAINS REGIONS OF BOTH HETEROCHROMATIN AND EUCHROMATIN the eukaryotic chromosome in a eukaryotic cell undergoing interphase contains REGIONS OF BOTH HETEROCHROMATIN AND EUCHROMATIN heterochromatin is most abundant in the centromeric regions of the chromosomes HETEROCHROMATIN IS MOST ABUNDANT IN THE CENTROMERIC REGIONS OF THE CHROMOSOMES heterochromatin, v condensed, highly compacted regions of DNA that is also transcriptionally inactive, is most abundant within the centromeric regions of the chromosomes heterochromatin is most abundant in the centromeric regions of chromosomes heterochromatin, the very compacted, v condensed dna that is not transcriptionally active is found abundantly within the centromeric regions of chromosomes within the centromeric regions of chromosomes, you will find an abundance of heterochromatin, very condensed and compacted, nontranscriptionally active regions of chromosomes (v dense and cannot partake in genetic transcription) CONSTITUTIVE HETEROCHROMATIN what is constitutive heterochromatin constitutive heterochromatin refers to CHROMOSOMAL REGIONS THAT ARE ALWAYS HETEROCHROMATIC AND PERMANENTLY INACTIVE IN REGARDS TO THEIR ABiLITY TO PARTAKE IN GENETIC TRANSCRIPTION these sequences of constitutive heterochromatin, constitutively heterochromatic regions are chromosomal regions THAT ARE ALWAYS PERMANENTLY HETEROCHROMATIC constitutive heterochromatin is always heterochromatic, and cannot partake in genetic transcription ever due to being constantly and permanently heterochromatic they are permanently far too dense and compacted to unwind and partake in the process of genetic transcription that requires both the compaction and decompaction of DNA (the latter of which constitutive heterochromatin cannot partake in) constitutive heterochromatin remains permanently heterochromatin, densely compacted and transcriptionally inactive constitutive heterochromatin DESIGNATES regions of chromosomes that remain heterochromatic, that remain v condensed and compacted, and remain permanently transcriptionally inactive, sections of chromosomes that can never partake in genetic transcription CONSTITUTIVE HETEROCHROMATIN EXAMPLES examples of constitutive heterochromatin constitutive heterochromatin include, regions of constitutive heterochromatin usually include HIGHLY REPETITIVE DNA sequences such as tandem repeats, rather than gene sequences constitutively heterochromatic regions of chromosomes usually contain highly repetitive sequences of dna such as tandem repeats, that can be permanently compacted and transcriptionally active without dramatically affecting an organism FACULTATIVE HETEROCHROMATIN facultative heterochromatin refers to chromatin that can occasionally INTERCONVERT BW HETEROCHROMATIN AND EUCHROMATIN facultative heterochromatin refers to regions of chromosomes that CAN OCCASIONALLY SWITCH IN BW HETEROCHROMATIN AND EUCHROMATIC they can be heterochromatic chromosomal regions or euchromatic chromosomal regions, they are able to switch in bw the two what is an example of facultative heterochromatin, a term designating regions of chromosomes that are not permanently compacted, that are able to vacillate bw the state of heterochromatin and euchromatin, facultative heterochromatin is able to switch between being heterochromatic and euchromatic rather than remaining in one state what is an example of facultative heterochromatin an example of facultative heterochromatin is the Barr body this occurs in female mammals when one of the two X chromosomes is converted into a HETEROCHROMATIC Barr body it is condensed and compacted and not transcriptionally active one of the X chromosomes in each of a female mammal's somatic cells is converted into a Barr body, a chromosome that is compacted and condensed, and not transcriptionally active the Barr body is transcriptionally inactive the conversion of one X chromosome from euchromatin, decompacted and transcriptionally active, to heterochromatin, compacted and transcriptionally inactive occurs during EMBRYONIC DEVELOPMENT IN THE SOMATIC CELLS OF THE BODY an x chromosome vacillates and switches from euchromatin to heterochromatin (and is therefore designated as facultative heterochromatin) within somatic cells during embryonic development

goodness of fit

how well the observed data and the predicted data match up evaluating the goodness of fit is the rational behind a statistical genetic approach

human abnormalities in chromosome number

human abnormalities in chromosome number are influenced by the age of the parents human abnormalities in chromosome number are influenced by the age of the parents in humans, the age of the parents influences the abnormalities in chromosome number older parents are considerably and substantially more likely to produce offspring, to produce children with abnormalities in chromosome number older parents are considerably and substantially more likely to produce offspring, to produce children with abnormalities in chromosome number older parents are considerably and substantially more likely to produce offspring, to produce children with abnormalities in chromosome number, they are substantially more likely to produce abnormalities in chromosome number down syndrome is an example of this, of how older parents are more likely to produce offspring with abnormalities in chromosome number, down syndrome is an example of how the age of the parents can substantially impact chromosome number abnormality in the offspring that they produce the common form of this disorder, the common form of Down syndrome is caused by the inheritance of three copies of chromosome 21 the common form of this disorder, the common form of Down syndrome is caused by the inheritance of three copies of chromosome 21, the inheritance of three copies of chromosome 21 in an offspring is the most common form that Down syndrome comes in the incidence of Down syndrome in offspring rises with the age of either parent in males however the rise occurs relatively late in life, usually past the age that the majority of men have children there is a risk in males producing offspring with Down syndrome that is more substantial later in life, but this risk and trend shows itself quite late in a male's life, past the age that the majority of males have children by comparison, the likelihood of having a child with down syndrome rises dramatically during a women's reproductive age the likelihood of having a child with down syndrome rises dramatically during a woman's reproductive age the likelihood of having a child with down syndrome rises dramatically during a woman's reproductive age, during the period of her life when she usually and is able to produce offspring this syndrome was first described by the English physician John Langdon Down in 1866 the association bw maternal age and Down syndrome was later discovered by L.S. Penrose in 1933 the syndrome, Down syndrome was first described by the English physician John Langdon Down in 1866 the association bw maternal age and down syndrome was later discovered by L.S. Penrose in 1933, and this relationship that he discovered bw maternal age and Down syndrome in 1933 was discovered even before the chromosomal basis for this disorder was identified by the French scientist Jerome Lejeune in 1959 the chromosomal basis for down syndrome was identified by Jerome Lejeune in 1959, but the relationship bw maternal age and Down syndrome was discovered earlier in 1933 by L.S. Penrose despite the chromosomal basis for this condition being discovered much later Down syndrome IS CAUSED BY NONDISJUNCTON Down syndrome is caused by nondisjunction Down syndrome is most commonly caused by nondisjunction what is nondisjunction nondisjunction means that the chromosomes do not segregate properly nondisjunction means that chromosomes do not segregate properly (this probs references the fact that chromosome 21 does not segregate properly, the copies of chromosome 21 do not segregate properly during gamete formation, and when this gamete combines with a genetically normal gamete, the resulting embryo will have that improper number of chromosome 21, the three copies of chromosome 21 that lead to Down syndrome) in this particular case of down syndrome, the nondisjunction of chromosome 21, the improper segregation of chromosome 21 most commonly occurs during meiosis I in the oocyte, in the egg inn particular, the nondisjunction of chromosome 21 usually occurs during meiosis I in the oocyte the nondisjunction of chromosome 21 that results in a gamete with 3 copies of chromosome 21 that leads to Down syndrome usually occurs during meiosis I within the oocyte THERE ARE DIFFERENT HYPOTHESES THAT HAVE BEEN PROPOSED TO EXPLAIN THE RELATIONSHIP BW MATERNAL AGE AND Down syndrome there are different hypothesis that have been proposed to explain the relationship bw maternal age and Down syndrome there are different hypotheses that have been proposed in order to explain the relationship bw maternal age and Down syndrome there are different hypotheses that have been proposed in order to explain the relationship bw maternal age and Down syndrome there is one popular idea that suggests that the occurrence of Down syndrome in relation to maternal age may be due to the age of oocytes one popular propose theory suggests that the relationship bw Down syndrome and maternal age may be due to the age of oocytes human primary oocytes are produced within the ovary of the female fetus prior to birth, and then are arrested at prophase of meiosis I how are human primary oocytes produced human primary oocytes are produced within the ovary of the female fetus, within the ovaries of the female fetus prior to birth and then these produced oocytes are arrested at prophase I of meiosis I, so during gametogenesis during the formation of these oocytes in the ovaries of the female fetus, these oocytes are arrested at prophase I of meiosis I, and they remain in this stage, arrested at prophase I of meiosis I until ovulation, until the time of ovulation therefore as a woman age, her primary oocytes, those oocytes that were arrested at prophase I of meiosis I when they were being formed in her ovaries when she was a fetus, these primary oocytes have been in prophase I for a progressively longer period of time as a woman ages, her primary oocytes have been in prophase I for a progressively longer period of time, they have remained arrested in prophase I of meiosis I for a progressively longer period of time this added length of time may contribute to the increased frequency of nondisjunction, this added length of time may contribute to the increased frequency of nondisjunction this added length of time that the primary oocytes have remained arrested in prophase I of meiosis may contribute to the increased frequency of nondisjunction about 5 percent of the time, Down syndrome is due to an extra paternal chromosome about 5 percent of the time, Down syndrome is due to an extra paternal chromosome about 5 percent of the time, Down syndrome is due to an extra paternal chromosome there are prenatal tests that can determine if a fetus has Down syndrome and some other genetic abnormalities there are prenatal tests that can determine if a fetus has Down syndrome and other genetic abnormalities there are prenatal tests that can determine if a fetus has Down syndrome and other genetic abnormalities there are prenatal tests that can determine if a fetus has Down syndrome and other genetic abnormalities

phenylketonuria

humans possess a gene that encodes the enzyme phenylalanine hydroxylase most people have 2 copies of this gene, and if an individual has 1 or 2 copies of this gene, then they can eat foods containing the amino acid phenylalanine bc the enzyme that those genes code for, phenylalanine hydroxylase, metabolizes the phenylalanine in the food the individual is consuming there is a mutation, where there is a rare variation in the sequence of the phenylalanine hydroxylase gene this variation in the sequence of the gene coding for the phenylalanine hydroxylase enzyme results in a nonfunctional version of phenylalanine hydroxylase the enzyme itself exists and is produced for (a process instigated by the genes coding for it) but due to the rare variation in genetic code, the enzyme is not functional and the individual can therefore not breakdown the amino acid phenylalanine if there are 2 copies of this gene, the individual is unable to properly breakdown the amino acid phenylalanine 1/8000 births amongst Caucasians it occurs when the individuals with the two defective copies of the gene proceed on a diet filled with the amino acid phenylalanine, it accumulates, and gets converted into phenylketones, which are detected in the urine PKU individuals- have a variety of detrimental traits: -mental retardation -under-developed teeth -foul-smelling urine there is a solution to this: it is where individuals with the two defective copies of this gene have the condition identified when they are born (possibly by testing the urine for the phenylketones, or genetic screening that can tell them if the child has the two defective genes) the PKU individuals are raised on a low phenylalanine diet so they are not exposed to compounds they can't digest they develop normally the environment and an individual's gene are therefore both important in the traits an organism has and expresses CHROMOSOME 12 is the chromosome that carries the gene that encodes phenylalanine hydroxylase

identification of dna as the genetic material

identification of dna as the genetic material identification of dna as the genetic material in order to fulfill its role, the genetic material must meet four criteria in order to fulfill its role, the genetic material must meet 4 criteria in order for it to fulfill its role, the genetic material must meet four criteria in order to be designated as and recognized as genetic material in order for it to fulfill its role, the genetic material must meet four criteria in order to be designated as and recognized as genetic material in order for it to fulfill its role and be identified as genetic material, the genetic material must meet and fulfill 4 criteria 1. INFORMATION: the genetic material must contain the information necessary in order to construct an entire organism the genetic material must contain the information necessary in order to construct an entire organism the genetic material must contain the information necessary I order to construct and build an entire organism the genetic material must contain the information necessary in order to construct and build an entire organism the genetic material must contain the information necessary in order to construct and build an entire organism in other words, the genetic material must provide the blueprint in order to influence and function as the determinant for the characteristics of an organism, the inherited traits of an organism the genetic material must provide and function as the blueprint that influences and functions as the determinant for the characteristics of an organism, act as the blueprint that functions as the determinant for the inherited characteristics of an organism 2. TRANSMISSION: during reproduction, the genetic material must be passed from parents to offspring during the process of reproduction, the genetic material must be passed from parents to offspring during the process of reproduction, the genetic material must be passed from parents to offspring during the process of reproduction, the genetic material must be passed from parents to offspring d during the process of reproduction, the genetic material must be past from parents to offspring, transmission during the process of reproduction, the genetic material must be passed from parents to offspring during the process of reproduction, this is known as transmission 3. REPLICATION: because the genetic material during the process of reproduction is passed from parents to offspring (this is identified as the phenomenon of transmission) because the genetic material during the process of reproduction is transmitted, passed from the parents to the offspring, and from the mother cells to the daughter cells during mitotic division, during the development of the embryo, the replication of the initial cell consisting of the egg cell and sperm uniting with one another, the mitotic division, and cellular replication and propagation that occurs until there is a fully developed and functional organism that can be born and function as its own individual entity, due to these processes of mitosis and meiosis and what they involve, the replication of dna in order to propagate cells, and the transmission of genetic material from the somatic cells of an individual to its gametes that will function in the development of a new organism, genetic material must be able to be copied 4. VARIATION: within any species, a significant amount of phenotypic variability occurs within any species, a significant and substantial amount of phenotypic variability occurs within any species, a significant amount of phenotypic variability occurs within a species an example of this phenotypic variability that regularly occurs within a species an example of this expected phenotypic variability that regular occurs within a species an example of this expected phenotypic variability that regularly occurs within a species is found among Mendel's experimentation Mendel studied several characteristics in pea plants Mendel studied several characteristics in pea plants that varied among different plants Mendel studied several characteristics within pea plants that varied among different plants Mendel studied several characteristics with pea plants that varied among different plants these characteristics that he studied within pea plants that varied among pea plants of the same species were: height- tall vs dwarf, these were the two variants of the trait of height the two variants of the trait of height were tall and short seed color- yellow vs green the genetic material needs to vary in ways that can account for the observed and established phenotypic differences and variation within each species the genetic material needs to vary in ways that can account for the observed and established phenotypic differences and variation within each species the genetic material needs to vary in ways that can account for the observed and established phenotypic differences and variation found within each species the genetic material needs to vary in ways that accounts for and sufficiently explains the established and observed phenotypic differences found in each species along with the work and experimentation that Mendel conducted, there were many other experiments conducted, and the data collected from those experiments conducted in the 1900s aligned and were consistent with the four aforementioned properties of information, transmission, replication, and variation the data collected in the 1900s from the experimentation of scientists besides Mendel who were attempting to establish governing genetic principles, this data collected, these experiments were consistent with these four established properties for genetic material; information, transmission, replication, and variation however, the experimental studies of genetic crosses, the crossing of individuals and production of offspring, as well as genetic analysis of both the offspring and parents is not sufficient by itself, to identify the exact chemical nature of genetic material and establish governing principles for genetic material in the 1800s, August Weismann and Carl Nägeli championed the idea that there is a chemical substance within living cells that is responsible for the transmission of traits from parents to offspring in the 1800s, August Weismann and Carl Nägeli championed the idea that there is a chemical substance within living cells that is responsible for the transmission of traits that occurs from parents to offspring there is a chemical substance within living cells that is responsible for the transmission of traits from parents to offspring, this hypothesis was proposed by August Weismann and Carl Nageli in the 1800s, they proposed the idea that a chemical substance within living cells is responsible for the transmission fo traits from parents to offspring the chromosome theory of inheritance was developed then after this proposal that a chemical substance within cells is responsible for the transmission of characteristics and traits from parents to offspring there was implemented experimentation that demonstrated that chromosomes are the carriers of the genetic material there was implemented experimentation that demonstrated that chromosomes are indeed the carriers of the genetic material nevertheless, the story was not complete, and it was not complete because chromosomes contain both the components DNA and protein, these two components of DNA and protein come together in order to produce chromosomes also, RNA is found in the vicinity of chromosomes RNA is found in the vicinity of chromosomes RNA is found in the vicinity of chromosomes therefore there was further research that need to be implemented in order to precisely identify the genetic material, due to the components of DNA and proteins being found within chromosomes, and RNA being in close proximity to chromosomes further distinctions had to be made and implemented in order to distinguish bw these genetic materials and their respective roles, distinctions that were more complex and in depth than simply the chromosomal theory of inheritance that pointed out that chromosomes are the carriers of genetic materials and therefore integral in regards to the passing on of traits from parents to offspring further research was required in order to precisely identify and designate the genetic material, to distinguish bw DNA, proteins, and RNA, because of the fact that the chromosomal theory simply pointed out that the structures responsible for the inheritance of genetic material and therefore the inheritance of the characteristics influenced by and coded for by that genetic material were chromosomes, and chromosomes are structures that are a conglomeration of DNA and proteins, and RNA is found in close proximity to chromosomes therefore a method was required by which scientists could distinguish bw DNA, proteins, and RNA

hypothesis testing outcomes

if the observed and predicted data match up really well, then we can conclude that the hypothesis is consistent with the observed outcome, we can accept the hypothesis that the trait aligns with particular governing principles of genetics this does not however prove a hypothesis correct, rather a hypothesis likely STATISTICAL METHODS CAN NEVER PROVE A HYPOTHESIS CORRECT statistical methods can show a hypothesis as likely, because the observed data is consistent with the hypothesis however there may be other hypotheses that are also consistent with the observed data, and may serve as the correct explanation for the results observed if there is a high deviation bw observed results and the hypothesis, the experimenter will most likely test a different hypothesis

Mendelian inheritance patterns prediction

in Mendelian inheritance patterns, there are genes that directly influence and impact the expression of a particular phenotype these genes and the manner in which they influence the phenotypic expression of traits is governed by Mendelian inheritance patterns/laws (the expression of these traits by the allelic combinations of these genes obey Mendelian law, they align with the governing principles of Mendelian genetics in order to predict the phenotype of an organism we need to consider the following factors: - the dominant-recessive relationship of alleles (if there are dominant alleles and recessive alleles) - gene interactions (the interaction of two genes, them influencing one another that may influence the phenotypic expression of a trait) - sex (the influence of sex, whether or not a trait is sex-linked) - environment (the influence of the environment on the expressivity of a trait- an example would be an individual with PKU that is unable to metabolize phenylalanine, and so the doctors when they discover this individual has PKU prescribe them a phenylalanine-free diet, so that they can live their lives without being impacted by the condition, so the expressivity of this phenotypic trait is very low) it is important to understand the environmental impact on the phenotypic trait, the ways in which an environmental shift can affect the phenotypic trait and whether or not the individual expresses it or a different phenotypic trait

haploinsufficiency

in cases of haploinsufficiency, the mutant allele is a LOSS-OF-FUNCTION allele the terms haploinsufficiency describes the patterns of inheritance (recall these are patterns of inheritance that substantially differ from the established Mendelian patterns of inheritance) where there is a heterozygote with an allelic combination of one functional allele and one inactive, nonfunctional allele this heterozygote exhibits an abnormal or disease phenotype an example of haploinsufficiency and its connection to dominant mutant alleles: polydactyly is a condition in humans, where a heterozygous individual (containing the active, functioning allele coding for polydactyly and then a nonactive allele) displays the phenotypic trait of polydactyly, and has extra fingers or toes

extranuclear inheritance and its effects on reciprocal crosses

in diploid eukaryotic species (eukaryotic species with all organisms within that species containing cells with two sets of chromosomes, one set inherited maternally, and the other inherited paternally), most of the genes within this species obeys and follows a Mendelian pattern of inheritance they follow a Mendelian pattern of inheritance due to the separation of homologous pairs of chromosomes during the formation of an organism's gametes (resulting in haploid gametes that will come together with other haploid gametes to form a diploid zygote, but the main focus here is the segregation of alleles of genes that occurs within the separation of homologous pairs of chromosomes, resulting in each gamete of an organism containing 1 allele per gene that will be passed on to the offspring to compete/interact with the other allele of each gene inherited from the other parent) the above process provides a tried and explanation for inheritance of genes found within the nucleus however, extranuclear inheritance simply does not follow a Mendelian pattern of inheritance this is due to the fact the mitochondria and chloroplast of cells are not sorted/segregated during the process of meiosis, and therefore there is no distinct and/or tried and true pattern of certain numbers of mitochondria and/or chloroplasts ending up within individual gametes Carl Correns in 1909 found a trait that did not follow a Mendelian pattern of inheritance this trait was pigmentation occurring within the four-o'clock plant, Mirabilis Jalapa within the four o'clock plant, Mirabilis Jalapa, there are various forms of pigmentation that its leaves can take on, including: - green - white - variegated with both green and white sectors Carl Correns was able to approve through experimentation that the pigmentation of the offspring was determined by the maternal parent for example, if the maternal parent had white pigmentation, the offspring also had white pigmentation if the maternal maternal parent had green pigmentation, the offspring also had green pigmentation if the maternal parent had variegated green and white pigmentation, the offspring also had variegated green and white pigmentation the offspring's phenotype of pigmentation was determined by the mother THE PATTERN OF INHERITANCE THAT CARL CORRENS OBSERVED- A PARTICULAR TYPE OF EXTRANUCLEAR INHERITANCE DESIGNATED AS MATERNAL INHERITANCE MATERNAL INHERITANCE IS MARKEDLY DIFFERENT FROM MATERNAL EFFECT looking at chloroplast specifically- chloroplasts are a kind of plastid, and this plastid makes chlorophyll chlorophyll is a green photosynthetic pigment that makes the plant whose cells it is a part of green (due to green being the only pigment not absorbed, and therefore serving as the sole pigment reflected back) MATERNAL INHERITANCE OCCURS AMONGST CHLOROPLASTS- this phenomenon of maternal inheritance occurs bc the chloroplasts are inherited solely from the cytoplasm of the egg, the chloroplasts are only maternally inherited from the cytoplasm of the mother's haploid gametes therefore the mother is the sole determinant of the genotype and therefore phenotype of her offspring, as the offspring only inherits chloroplasts from her the pollen grains of Mirabilis Jalapa (the haploid gametes that come from the father) are not able to transmit chloroplasts to the offspring solely the cytoplasm of the egg (the haploid gamete that is contributed by the mother) contains chloroplasts, and thus the offspring inherit their chloroplasts from the cytoplasm of the egg of the mother

linkage and crossing over

in eukaryotic species, each linear chromosome contains a very long segment of dna in eukaryotic species, each linear chromosome contains a v long segment of dna that composes it each linear chromosome is composed of a long segment of dna in a eukaryotic species within a eukaryotic species, each linear chromosome is composed of a long segment of dna a chromosome contains many individual functional units, called genes that influence an organism's traits a chromosome contains many individual functional units, called genes that influence an organism's traits a chromosome contains many individual functional units, these individual functional units within chromosomes are designed as genes that influence the traits of organisms a typical chromosome is expected to contain many hundreds or perhaps a few thousand genes a typical chromosome is expected to contain many hundreds or perhaps a few thousand genes, hundreds many hundreds or perhaps a few thousand individual functional units that are designated as genes the term synteny means that two or more genes are located on the same chromosome THE TERM SYNTENY means that two or more genes are located on the same chromosome the term synteny means that two or more genes are located on the same chromosome the term synteny means that two or more genes are located on the same chromosome the term synteny means that two or more genes are located on the same chromosome the term synteny designates and means that two or more genes are located on the same chromosome genes that are syntenic are physically linked to one another, because each eukaryotic chromosome contains a single, continuous, linear molecule of DNA genes that are syntenic, meaning they are located on the same chromosome are also physically linked to one another, because each individual eukaryotic chromosome contains one continuous, linear molecule of DNA each individual eukaryotic chromosome contains one continuous linear molecule of dna and therefore if there are two genes that are syntenic, they are located on the same chromosome and are indeed physically linked to one another GENETIC LINKAGE what is genetic linkage genetic linkage is the phenomenon in which genes that are close together on the same chromosome tend to be transmitted as a unit genetic linkage is the phenomenon in which genes that are close together on the same chromosome tend to be transmitted as a unit genetic linkage is the phenomenon in which genes that are close together on the same chromosome tend to be transmitted as a unit therefore genetic linkage has an influence on inheritance patterns genetic linkage is the phenomenon in which genes that are close together on the same chromosome tend to be transmitted as a unit genetic linkage is the phenomenon in which genes that are located close together on the same chromosome tend to be transmitted as a unit genetic linkage therefore has an influence on inheritance patterns, as genetic linkage in the phenomenon in which two genes that are located close to one another on the same chromosome will be transmitted as a unit, will be transmitted as linked genes, which affects inheritance patterns CHROMOSOMES ARE SOMETIMES CALLED LINKAGE GROUPS chromosomes are sometimes called linkage groups chromosome are sometimes called linage groups why are chromosomes sometimes called linkage groups chromosomes are sometimes called linkage groups because a chromosome contains a group of genes that are physically linked to one another chromosomes are designated as linkage groups because a chromosome contains a group of genes that are physically linked together that are physically linked to one another chromosomes are designated as linkage groups because a chromosomic contains a group of genes that are physically linked to one another, a group of genes that are physically connected and linked to one another, this is why chromosomes are sometimes referred to as linkage groups, because they contain a multitude of chromosomes that are all physically linked to one another, so they are technically considered groups of chromosomes that are linked to one another, linkage groups in species that have been analyzed and characterized genetically, in species that have been analyzed and characterized genetically, the number of linkage groups equals the number of chromosome types in species that have been analyzed and characterized genetically, the number of linkage groups equals the number of chromosome types in species that have been analyzed and characterized genetically, the number of linkage groups equals the number of chromosome types in species that have been analyzed and characterized genetically, the number of linkage groups equals the number of chromosome types, furthering the idea that chromosomes can be designated as linkage groups an example of this is that human somatic cells, human somatic cells have 46 chromosomes human somatic cells have 46 chromosomes, and these 46 chromosomes contained within human somatic cells are composed of 22 types of autosomes, 22 types of autosomes, autosomal chromosomes, 22 types of autosomes that come in pairs, plus one pair of sex chromosomes, the x and the y that are possibilities to fill this pairing therefore humans are considered to have 22 autosomal linkage groups, corresponding to those 22 different types of autosomes, all found in pairs totaling out to 44 chromosomes, 1 X chromosome linkage group, and males who have the xy combination in their allosomes, in their sex chromosomes will have the Y linkage group, as linkage groups are identified and established as being separate and distinct entities therefore within the human genome there have been 24 linkage groups identified, 22 autosomal linkage groups, 1 X chromosome linkage group, and 1 Y chromosome linkage group in addition to this the human mitochondrial genome is another linkage group in addition to this the human mitochondrial genome is another linkage group, bringing the total count of linkage groups identified within the human genome to 25 geneticists are often interested in the transmission of two or more characters, two or more traits within a genetic cross geneticists are often interested in the transmission of two or more characters, or two or more traits within a genetic cross when a geneticist follows the variants of two different characters/traits within a cross, this is designated as a dihybrid cross when there are the variants of three characters/traits being followed, this cross is designated as a trihybrid cross this designation goes so on and so forth the outcome of a dihybrid cross or trihybrid cross depends on whether or not the genes are linked to one another along the same chromosome the outcome of a dihybrid cross or a trihybrid cross depends upon whether or not the genes that are being analyzed and coding for the traits/characters that are being followed are linked to one another along the same chromosome or not, this will affect the results of a dihybrid or trihybrid cross

the procedure for viewing chromosomes through light microscopy

in the example described in the book: the celled were obtained from a sample of human blood THE CELLS ARE OBTAINED FROM A SAMPLE OF HUMAN BLOOD more specifically, the chromosomes within lymphocytes LYMPHOCYTES ARE A PARTICULAR TYPE OF WHITE BLOOD. CELL the chromosomes within an individual's lymphocytes, an individual's white blood cells were examined BLOOD CELLS ARE DESIGNATED AS A TYPE OF SOMATIC CELL, A CELL OF THE HUMAN BODY THAT IS DIPLOID somatic cell definition reminder: a somatic cell is any cell within an organism that is not a gamete or a gamete precursor, a somatic cell is something other than a gamete or a gamete precursor what is the term to designate gametes? gametes, which can fall under the categories of sperm, egg, or their precursors are called GAMETES or GERM CELLS germ cells are gametes (sperm or eggs, or precursors to these gametes that fuse with one another during fertilization in order to form a diploid zygote) somatic cells tend to be diploid, gametes are haploid, that is why when two gametes (an egg and a sperm) come together and fuse during the process of fertilization they form a diploid zygote, a fully formed diploid cell that can then proliferate in order to form a fully developed diploid individual that will go on to develop its own gametes once the blood cells, specifically the lymphocytes, the white blood cells, have been removed from the body of an individual, they are TREATED WITH DRUGS these drugs that these white blood cells are treated with stimulates them and incites them to undergo mitotic division these drugs also caused the cell division they undergo to be paused during mitosis, paused during a particular phase, either prophase or metaphase then, these actively dividing cells that have been stopped and frozen at a particular phase of mitosis are subjected to centrifugation this centrifugation occurs in order to concentrate these white blood cells once the white blood cells have undergone centrifugation and become concentrated, this concentrated preparation is then mixed with a hypotonic solution the concentrated preparation of white blood cells is then mixed within a hypotonic solution, this hypotonic solution has a lower concentration of solute than the white blood cells themselves, and therefore water rushes into the white blood cells in order to equalize the concentrations of solute within the white blood cells and the hypotonic solution, and the cells swell due to filing up with the hypotonic solution the swelling of the cells causes the chromosomes to spread out within the cell, THE CHROMOSOMES SPREAD OUT WITHIN THE CELL DUE TO THE SWELLING OF THESE CELLS THAT OCCURS AS A RESULT OF THE SOLUTION THE CELLS ARE PUT IN BEING HYPOTONIC the chromosomes spread out within the swollen cell, and that makes it easier to see each individual chromosome, and distinguish them from one another the cells are then treated with a FIXATIVE the fixative that the swollen cells (whose compacted and coiled chromosomes have spread out due to the swelling in order to make them distinguishable from one another) are treated with CHEMICALLY FREEZES THEM the chromosomes are thus no longer able to move around, and are frozen in place, spread out and able to be distinguished the cells are then treated with a chemical dye, this chemical dye they are treated with binds to the chromosomes, and stains the chromosomes the dyeing of the chromosomes gives these chromosomes a distinctive banding pattern this distinctive banding pattern that the chromosomes get from being dyed ENHANCES THEIR VISUALIZATION AND THEIR ABILITY TO BE IDENTIFIED, makes them far more visible due to the dye, and even more distinguishable from one another due to the differences the demarcated and distinguishable differences bw their banding patterns (that are due to the genes and the conformation of those genes that you will find on each chromosome) then this burst, frozen, fixed, dyed cells are placed on a slide and microscopically examined through the utilization of a light microscope WITHIN A CYTOGENETIC LABORATORY, the microscopes that the cytogeneticists utilize in order to examine the burst cells and the chromosomes within these bust, frozen, fixed cells on a slide HAVE A CAMERA THAT IS ABLE TO PHOTOGRAPH THE CHROMOSOMES in recent years, there have been scientific and advantageous developments to microscopy that now allow cytogenetics to view microscopic images on a computer screen scientists are now able to view microscopic images on a computer screen once the scientists are able to get microscopic images of the chromosomes on a computer screen, individuals snapshots of all of the chromosomes they can designate and distinguish, they can then organize the chromosomes they have (using their microscopic images of them) and organize them by size from the largest chromosomes to the smallest chromosomes THE HUMAN CHROMOSOMES in the procedure given to us in the book are organized on a computer screen by size from the largest to the smallest a number is given to designate each type of chromosome, you will find two chromosomes for each type (2 per each of the 23 homologous pairs, 1 of each pair being inherited maternally, and 1 of each pair being inherited paternally) AN EXCEPTION the chromosomes that are not labeled with numbers are the chromosomes in the 23rd pair, the sex chromosomes (all of the other chromosomes are autosomal chromosomes) these are the allosomal chromosomes, the sex chromosomes, that can usually come in the pairing XX or XY A KARYOTYPE IS AN ORGANIZED REPRESENTATION OF THE CHROMOSOMES FOUND WITHIN A CELL an organized and distinguished representation of the chromosomes found within a particular cell the karyotype reveals the number of chromosomes within an actively dividing somatic cell, a cell that is undergoing mitosis

the oligosaccharides produced on the surface of red blood cells with differing blood types

in type O red blood cells, the tree is smaller than type A or type B- bc a sugar has not been attached to a specific site on either tree extending from the red blood cell with the trees on type A or type B red blood cells, they are larger due to a sugar being attached on a specific site on both of the trees, either N-acetyl-galactosamine for type A or galactose for type B explaining this difference on the molecular level: the gene that determines ABO blood type encodes an enzyme called glycosyl transferase, this enzyme glycosyl transferase attaches a sugar to the oligosaccharide the recessive lowercase i allele that codes for the O blood type carries a mutation that renders this enzyme glocsyl transferase (the enzyme responsible for attaching a sugar to the oligosaccharide) inactive and therefore incapable of doing its function of attaching a sugar to the oligosaccharide the alleles IA and IB coding for blood type A and B respectively code for two different types of the enzyme glycosyl transferase these two types of glycosyl transferase encoded for by the IA and IB alleles have different structures in their active sites (where the substrate needs to bind in order for the enzyme to do its function, which in this case is attach a sugar to the oligosaccharide) the active site of glycosyl transferase is the part of this enzyme that recognizes the sugar that will be attached by the enzyme to the oligosaccharide the IA allele codes for a glycosyl transferase that recognizes URIDINE DISPHOSPHATE N-ACETYLGALACTOSAMINE (UDP-GalNAc and attaches uridine diphosphate n-acetylgalactosamine to the oligosaccharide GalNAC- uridine diphosphate n-acetylgalactosamine is symbolized as a green hexagon, attached to the oligosaccharide on red blood cells of an individual with type A blood the IB allele codes for a glycosyl transferase that recognizes UDP-GALACTOSE and attaches this galactose to the oligosaccharide located on the surface of red blood cells of an individual with type B blood UDP-GALACTOSE is symbolized as an orange triangle thus the molecular structure of surface antigen B on red blood cells of an individual with type B blood is produced by the attachement of galactose by glycosyl transferase to the oligosaccharide on the surface of these red blood cells a person with type AB blood (the allelic combination of IAIB) makes both types of the glycosyl transferase enzyme, both the enzymes that recognizes the uridine diphosphate n-acetylgalactosamine and attaches GalNAc to the oligosaccharide and the enzyme that recognizes the UDP-galactose and attaches the galactose to the oligosaccharide therefore the red blood cells of an AB blood type individual have trees (oligosaccharides) with both GalNAc and galactose attached to them due to the two types of glycosyl transferase enzyme that the allelic combination IAIB codes for there is a small difference in the structure of the oligosaccharide namely the difference can be found in a GalNAc in antigen A vs the galactose in antigen B that is how these two antigens are different and distinct from one another at the molecular level therefore these antigens can be recognized, and more importantly be recognized as distinct from one another by anitibodies blood type A- their blood cells produce antibodies against blood type B (and recognize the B antigens on the surface of the B blood type individual's red blood cells) these antibodies against blood type b require a galactose in the oligosaccharide for their proper recognition, that is how these antibodies will recognize those antigens, and destroy those specific B blood type red blood cells therefore these antibodies will not destroy their own blood cells, as they are able to distinguish bw A and B antigens, and will destroy the red blood cells they find with B antigens on the surface blood type B- their blood cells will produce antibodies against blood type A (and recognize A antigens on the surface of an A blood type individual's red blood cells) blood type AB- their blood cells will not produce any antibodies against any antigens (bc red blood cells of AB individuals have both A and B antigens, so if they had antibodies recognizing either of these antigens, the antibodies would destroy the AB red blood cells in addition to A and B blood cells, AB blood types are universal accepters Blood type O- their blood cells will produce antigens against both A and B, as it the cells have neither on their surface therefore any other blood type can accept O (as well as other O blood types) due to the lack of recognizable (any at all) antigens on the surface of O red blood cells, and O is a universal donor but only accept other O blood

extranuclear inheritance

inheritance of genetic material outside of the nuclear, DNA within organelles such as mitochondria and chloroplasts is inherited, and due to these organelles being found in the cytoplasm of cells, the inheritance of genetic material from these organelles is designated as extranuclear or cytoplasmic inheritance

the organization of bacterial chromosomes

inside a bacterial cell, the CHROMOSOME OF THE BACTERIAL CELL IS HIGHLY COMPACTED the chromosome of the bacterial cell is highly compacted, and this bacterial cell's chromosome is located within a region known as the nucleoid region BACTERIA USUALLY CONTAIN A SINGLE TYPE OF CHROMOSOME bacteria usually contain a single type of chromosome, bacteria usually contain a single type of chromosome, however more than one copy of that single type of chromosome may be found within the bacterial cell more than one copy of that particular bacterial chromosome may be found within that bacterial cell depending on the growth conditions and the various phases of the cell cycle, BACTERIA ARE ABLE TO HAVE 1 TO 4 IDENTICAL CHROMOSOMES PER CELL bacteria are able to have 1 to 4 identical chromosomes per cell due to the growth conditions for these bacterial cells as well as the phases of the cell cycle that bacterial cells go through (how these phases occur, in what manner these phases occur and how often these phases occur) the number of copies varies depending on the bacterial species THE NUMBER OF COPIES OF CHROMOSOMES DIFFERS DEPENDING ON THE PARTICULARS OF THE BACTERIAL SPECIES the number of copies of chromosomes differs and changes as you move from one bacterial species to another recall that bacteria can have anywhere from 1 to 4 chromosomes per bacterial cell EACH CHROMOSOME within a bacterial cell occupies its own distinct nucleoid region, its own distinct space within the bacterial cell each chromosome within a bacterial cell occupies its own space within this bacterial cell THE BACTERIAL NUCLEOID IS DIFFERENT FROM THE EUKARYOTIC NUCLEUS the bacterial nucleoid is not a separate cellular compartment bounded by a membrane THE BACTERIAL NUCLEOID IS NOT A SEPARATE CELLULAR COMPARTMENT BOUNDED BY A MEMBRANE the eukaryotic nucleus is indeed an individual entity, an independent cellular compartment within the eukaryotic cell bounded by a membrane how the bacterial nucleoid is not a cellular compartment bounded by a membrane the DNA within a nucleoid region of a bacterial cell is directly in contact with the cytoplasm of the cell, it is never separated out in regards to contact from the rest of cell, the DNA of a bacterial cell is found within the nucleoid region, but is in consistent contact with the cytoplasm, as the nucleoid region is not an individualized cellular compartment

inversion heterozygotes

inversion heterozygotes may produce abnormal chromosomes due to the phenomenon of crossing over inversion heterozygotes may produce abnormal chromosomes due to the phenomenon of crossing over that occurs during meiosis I an individual carrying one copy of a normal chromosome and one copy of an inverted chromosome an individual carrying one copy of a normal chromosome and one copy of an inverted chromosome is identified as an inversion heterozygote an individual, with this one copy of a normal chromosome and one copy of an inversion chromosome, may present as phenotypically normal, however this inversion heterozygote may have a high probability of producing haploid cells that are abnormal in their total genetic content this inversion heterozygote, an individual containing one copy of a normal chromosome and one copy of an inversion chromosome, may present as phenotypically normal, however they may have a high probability of passing on this chromosomal inversion to their offspring and the inheritance of that chromosomal inversion affecting the phenotype of the offspring individuals who are an inversion heterozygote may have a high probability of producing haploid cells that are abnormal in their total genetic content individuals who are inversion heterozygotes may have a high probability of producing haploid cells that are abnormal in their total genetic content the underlying cause of gamete abnormality is the phenomenon of crossing over within the inverted region the underlying cause of gamete abnormality is the phenomenon of crossing over that may occur within the inverted region during meiosis I, particularly during prophase I, there is the phenomenon of crossing over that occurs pairs of homologous sister chromatids synapse with one another 2 pairs of homologous sister chromatids synapse one another and undergo the process of recombination and crossing over, they synapse with one another 2 pairs of homologous sister chromatids synapse with one another during meiosis I during prophase I for the normal chromosome and the inversion chromosome, the chromosome containing an inversion, an inversion loop must form in order to permit the homologous genes on both of the chromosomes, on both the normal chromosome in the homologous pair and the inversion chromosome in a homologous pair to align next to one another properly, despite the issue posed with an inverted genetic sequence an inversion loop is required in order for the homologous genes on both of the chromosomes to align with one another in order to undergo recombination despite the inverted sequence if a crossover occurs within the inversion loop that is created, highly abnormal chromosomes are produced if a crossover during recombination occurs within the inversion loop, highly abnormal chromosomes are produced a crossover in this region in the inversion loop region is likely to occur if the inversion is large therefore individuals that carry large inversions are more likely than individuals with small inversions to produce abnormal gametes individuals with larger inversions are more likely to produce gametes with abnormal genetic content than individuals with smaller inversions the consequences of this type of crossover occurring within an inversion loop depends on whether the inversion is pericentric, the centromere is located within the inverted segment of the chromosome, or paracentric the centromere is located outside of the inverted segment of the chromosome there can be a crossover in the inversion loop when one of the homologs has a pericentric inversion, an inversion where the centromere lies within the inverted chromosomal segment pericentric homolog where the centromere lies within the inverted region of the chromosome this event consists of a single crossover, and this single crossover involves two of the four sister chromatids this single crossover involves two of the four sister chromatids following the completion of the process of meiosis, the single crossover that involves only two of the four sister chromatids yields two abnormal chromosomes both of these abnormal chromosomes have a segment that is deleted and a different segment that is duplicated there are two abnormal chromosomes due to one of the chromosome one of the chromosomes within the homologous pair having a pericentric inversion, and inversion where the centromere of this chromosome is located within the chromosomal segment that is inverted there is one chromosome that results with a duplication, and one chromsome that results in a deletion when there is a crossing over bw one sister chromatid of each pair that I occurring, only 2 sister chromatids total out of the four are participating in a crossover between a sister chromatid with no inversion and a chromatid with a pericentric inversion, where the centromere is located within the inverted chromosomal segment this results in 2 completely chromosomes with no additional chromosomal aberration, one completely normal chromosome from the pair of sister chromatids that was normal, and one chromosome from the other pair of sister chromatids that contained a chromosomal inversion this chromosome maintains this chromosomal inversion but has not acquired any additional chromosomal aberrations due to not participating in the crossover then there are 2 other chromosomes resulting, that resulted from the crossing of those 2 sister chromatids of distinct pairs that did participate in crossing over both of these resulting chromosomes has a duplication and a deletion due to crossing over occurring within an inversion loop one of the abnormal chromosomes that contains a duplication and deletion is missing the genes H and I, and it has an extra copy of genes A, B, and C the other abnormal chromosome also has a duplication and deletion, but is experiencing the opposite situation this other abnormal chromosome is missing genes A, B, and C, and it has extra copies of H and I these abnormal chromosomes that will be placed in gametes due to meiosis may result in inviable gametes, that will not contribute to reproduction or help reproduction to proceed and finish if it does form a zygote with another gamete however, if these abnormal chromosomes are sonhow passed to offspring, they are likely to produce phenotypic abnormalities, depending on the amount and the nature of the duplicated and deleted genetic material in these chromosomes within gametes that contribute to reproduction depending on the amount and nature of the duplicated and deleted genetic material within these chromosomes that end up in gametes, the offspring that is formed from the gamete containing either of these abnormal chromosomes containing duplications and deletions may accrue some phenotypic abnormalities a large deletion may be lethal, is likely to be lethal what about the outcome of a crossover occurring in an inversion loop in a situation where there is a paracentric inversion, and the centromere is lying outside of the chromosomal segment that is inverted there is a paracentric inversion in one of the pairs of sister chromatids, where the centromere lies outside of the inverted region this single crossover event where there is a paracentric inversion where the centromere is located outside of the inverted region, outside of the inverted chromosomal segment, this single crossover event occurring within the inversion loop produces a very strange outcome one resulting chromosome is a DICENTRIC CHROMOSOME CONTAINING TWO CENTROMERS one resulting chromosome is dicentric, a dicentric chromosome, containing two centromeres the region of the chromosome that connects the centromere of this one chromosome is designated as a dicentric bridge the region of the chromosome that is connecting the two centromeres is a dicentric bridge this one resulting chromosome has two centromeres and therefore is designated as a dicentric chromosome the region of the chromosome connecting the two centromeres is a dicentric bridge the crossover also produces another resettling chromosome, a piece of chromosome without any centromere at all (probably due to one of the resulting chromosomes, the other chromosome that accrued additional chromosomal aberrations due to participation in crossing over, having two centromeres being designated as dicentric, and having a dicentric bridge connecting the two centromeres) the acentric fragment, the chromosome with no centromere, will be lost and degraded in subsequent cellular divisions the dicentric chromosome is a temporary condition if the two centromeres try to move towards opposite poles during anaphase, the dicentric bridge will be forced to break at some random location if the two centromeres try to move towards opposite poles during anaphase, the dicentric bridge will break at some random location because of anaphase pulling the dicentric chromosome apart, the two chromosomes trying to move to opposite poles of the cell the net result of this crossover therefore due to the production of an eccentric chromosome that will degrade and be lost during subsequent cellular divisions, as well as a dicentric chromosome whose two centromeres will probably attempt to move to opposite poles of the and result in the dicentric bridge, the portion of the chromosome connecting the two centromeres to break in a random location the net result of this crossover will produce one normal chromosome, one chromosome with an inversion, and two chromosomes that contain deletions these two chromosomes with deletions result from the random break in the dicentric bridge of the dicentric chromosome that will occur when the two centromeres of the chromosome move apart and migrate to opposite poles, and this causes a random break in the dicentric bridge, resulting into two chromosomal segments, two chromosome with deletions, and they are missing the genes that were located on the acentric fragment, the chromosome that due to a lack of a centromere (that resulted from one of the resulting chromosomes having two centromeres) was subsequently lost and degraded in subsequent cellular divisions

primary advantage of sexual reproduction

it enhances genetic variation the example given is that a couple, with one blue eyed, tall individual and a brown-eyed, short individual, the offspring could have new combinations (more genetic variations) with different pairings of the eye color and height traits there can be new trait combinations that didn't exist in either of the parents, therefore offspring are not genetically identical to either parent, but rather a mixture with genetic variation thrown in as well genetic variation can be advantageous in terms of survival and competition within a natural environment biological evolution/evolution- refers to the phenomenon that genetic mutations within a population may change from one generation to the next , depending on those factors of the kinds of genetic mutations that occur, and the environmental response of propagating this mutation as it is advantageous, or wiping it out an example of biological evolution- random gene mutations over the course of generations of giraffes have resulted in the neck of a giraffe lengthening, this lengthened neck enabling them to feed on leaves located high up in trees this genetic mutation and resulting trait has become prevalent amongst giraffes bc it is a beneficial one, and the giraffes with this trait are more likely to survive and reproduce, passing the beneficial allele of a long neck on to the offspring the above process is natural selection, and it results in a species being more in tune with its environment an accumulation/conglomeration of genetic changes can lead to dramatic changes in species morphology an example of this is the evolution of the modern day horse, it includes an increase in size, less toes, and a modified jaw

genetic approach

it is the approach that occurs and is implemented in order to answer a research question molecular geneticists often choose to focus on mutant genes with an abnormal function this often includes looking at genetic mutations that eliminate the function of the gene LOSS OF FUNCTION MUTATION- a mutation that results in a gene losing its function LOSS OF FUNCTION ALLELE is what that mutated gene is now known as, as it can no longer function properly if you look at these mutations that cause genes to no longer function, you can figure out what the functions of those genes are when they are functioning normally an example of this is a specific plant species producing purple flowers if there is a loss of function mutation, causing a gene to lose its functions, and the plant with that loss of function mutations presents with white flowers, then we understand that the functional gene (the gene when functioning) contributes to and implements the purple color of the flower, and when there is a loss of function mutation, that causes the gene to not function, and the flowers to be white therefore our understanding is that that gene is responsible for the purple flower color, and the absence of the functionality of this gene, or the gene itself, results in a white flower

blood type inheritance

look at a cross bw parents with the allelic combinations IAi and IBi look at notes to see the outcome of this cross with a Punnet Square the outcomes are IAIB (type AB), IAi (type A), IBi (type B), ii (type O) in a 1:1:1:1 ratio

maternal effect and Drosophila melanogaster

maternal effect genes have been identified within the fly species drosophila melanogaster in these organisms, there is a short generation time geneticists have been able to find mutant alleles within the Drosophila melanogaster species that prevent Drosophila melanogaster fly embryos from developing properly these mutant alleles interfere with proper embryonic development and stop the embryos from developing as they normally would (recall that mutations in maternal effect genes are particularly deadly due to the fact that the allelic combination of the maternal effect gene that comes from the mother is the sole determinant of the phenotype expressed by all of that mother's offspring, therefore if there is a mutant allele in that maternal effect gene in the allelic combination of the mother, then the offspring will have a dramatically altered and probably detrimental phenotype) there are several maternal effect genes that all have substantial effects on the phenotype expressed by the offspring, and have this effect due to their extreme influence on Drosophila melanogaster embryonic development the pattern of Drosophila melanogaster embryonic development occurs along axes: - anteroposterior axis - dorsoventral axis the proper development of each of these axes require a distinct particular distinguishable set of maternal gene products (so those gene products produced and provided by the nurse cells surrounding the maturing oocyte that are transferred into the maturing oocyte and influence it through fertilization and zygote development) the maternal effect gene designated as bicoid produces a gene product that accumulates in a specific region of the maturing oocyte, a specific site of the egg the region of the egg where the product of the gene bicoid settles is v important bc this region where this gene product conglomerates and remains will eventually develop into the anterior structures of the developing embryo if there are mutant alleles of these maternal effect genes, this will most likely lead to abnormalities in the anteroposterior or dorsoventral pattern of embryonic development this is a serious issue, the pattern of embryonic development being impacted by the mutant alleles of maternal effect genes that are the sole determinants of the phenotypic expression of a particular conformation/pattern of the Drosophila melanogaster embryonic growth in mice and humans, there have been several maternal effect genes that have been identified in these organisms (remember recently, maternal effect genes have been discovered in mice and humans) these maternal effect genes wield a lot of impact and influence on the embryonic development of mice and humans

mitochondrial DNA

mitochondrial DNA is also designated as mtDNA each copy of the entire mitochondrial chromosome consists of: - a circular DNA molecule - this circular DNA molecule is only 17,000 base pairs in length the size of the mitochondrial chromosome is apparently very tiny (in regards to it being composed of only 17,000 base pairs, and that composing essentially the entirety of the mitochondrial genome), and its size is less that 1 percent of a typical bacterial chromosome (so bacterial chromosomes are much larger than mitochondrial chromosomes) the human mitochondrial DNA does not carry a substantial number of gene the human mitochondrial DNA contains 13 genes encoding proteins that have some sort of function necessary within the mitochondrion itself human mitochondrial DNA also carries genes that code for ribosomal and transfer RNA so in addition to those 13 genes the mtDNA codes for that produce proteins that function in various ways within the mitochondrion, there are also genes within the mtDNA that codes for ribosomal and transfer RNA the ribosomal and transfer RNA coded for by the genes within mtDNA are necessary for the synthesis of the 13 proteins/polypeptides that are also coded for by other genes in the mtDNA the primary function of mitochondria: to provide the cells with the majority of the adenosine triphosphate ATP that they possess ATP is a molecule that functions as an energy source, and this energy source ATP is utilized in order to implement various cellular functions that require energy the 13 polypeptides that are coded for by genes in the mtDNA are all subunits of proteins that function within the process of oxidative phosphorylation oxidative phosphorylation is a process in which mitochondria utilize oxygen in order to synthesize ATP (this particular refers to the use of oxygen as the final electron acceptor in the electron transport chain pathway) apparently the 13 polypeptides coded for by genes in the mtDNA are subunits of the proteins involved in oxidative phosphorylation, therefore they are subunits of proteins involved in the synsthesis of ATP however, it is important to note that mitochondria require a multitude of proteins (more than just those that the 13 polypeptides coded for by genes in the mtDNA are subunits of) in order to implement the process of oxidative phosphorylation, as well as various other mitochondrial functions many mitochondrial proteins (proteins that function within the mitochondria) are coded for by genes found within the genetic material of the cell's nucleus when these genes in the genetic material within the cell's nucleus are expressed, the mitochondrial polypeptides (that will form those proteins that will do all those mitochondrial functions) are created outside of the mitochondria in the cytosol then, once these mitochondrial polypeptides are created, they are transported into the mitochondria where they will join with other polypeptides in order to make functional mitochondrial proteins that will function within the mitochondria

mitochondrial diseases

mitochondrial diseases can occur in two ways in some cases, the mitochondrial mutations that result in mitochondrial diseases are mitochondrial mutations transmitted maternally, from the mother to the offspring human mitochondrial DNA is maternally inherited because it is transmitted from mother to offspring via the cytoplasm of the egg within the cytoplasm of the egg, there is the maternal human mitochondrial DNA, that is transmitted to the offspring when a zygote is formed, human mitochondrial DNA is therefore only inherited maternally therefore it has been concluded that the transmission of inheritable human mitochondrial diseases does not follow a classic Mendelian pattern of inheritance, or align with any Mendelian laws rather, the transmission of inheritable human mitochondrial diseases occurs alongside/under the phenomenon of maternal inheritance in addition to the transmission of these human mitochondrial diseases following a maternal inheritance phenomenon pattern of inheritance, there are mitochondrial mutations that may occur within somatic cells, and these mitochondrial mutations within somatic cells can proliferate and conglomerate as the individual developing these mitochondrial mutations ages researchers have concluded and discovered that mitochondria are particularly susceptible to DNA damage, they are susceptible to DNA mutations how do these DNA mutations occur? when more oxygen is consumed than is actually used in order to synthesize energy in the form of ATP, what happened is the mitochondria (having consumed more oxygen than its used in order to produce energy in the form of ATP) tends to produce free radicals that can and will destroy and damage the DNA unlike nuclear DNA, mitochondrial DNA has far less repairing capabilities (is less capable of repairing its DNA and does not have the multitude of mechanisms that nuclear DNA does in order to reverse damage or somewhat repair damaged DNA), and it doesn't have any protective mechanisms in place to protect it against the damage inflicted by the free radicals that it creates due to consuming more oxygen than it actually uses during the synthesis of energy in the form of ATP there is a multitude of mitochondrial diseases, these diseases have been discovered in humans these mitochondrial diseases are caused by mutations within mitochondrial genes there are over 200 diseases associated with defective mitochondria (mitochondrial DNA mutations) that have been discovered these mitochondrial diseases caused by mutations in the mitochondrial genome are usually CHRONIC DEGENERATIVE DISORDERS chronic degenerative disorders are usually disorders that affect cells that require a large amount of energy in the form of ATP (cells that will therefore most likely contain plenty of mitochondria, and therefore plenty of possibility for genetic mutations within the mitochondrial genome) one example of a mitochondrial disease is LEBER HEREDITARY OPTIC NEUROPATHY (LHON) this mitochondrial disease affects the optic nerve (the nerve responsible in helping an individual to see), and the occurrence of this disease can lead to progressive loss of vision in one or both of the individual's eyes LHON Leber hereditary optic neuropathy can be caused by a defective mutation in one several mitochondrial genes (that could one could presume influence sight) researchers do not no for sure which mitochondrial genes specifically influence leber hereditary optic neuropathy, and they are still trying to understand exactly how a defect in these several mitochondrial genes causes an individual to have leber hereditary optic neuropathy an important and integral factor in mitochondrial disease is heteroplasmy recall hat heteroplasty is a condition designating that a cell contains within it a mixed population of mitochondria (perhaps a multitude of different types of mitochondria) when you are looking at an individual cell that is heteroplasmic (carrying many different kinds of mitochondria) it can contain mitochondria that carry a disease causing mutation (they are genetically mutated, and this causes a disease) other cells may not contain any mitochondria carrying disease causing mutations as cells divide, the mutant mitochondria (mitochondria carrying disease causing mutations) as well as the normal mitochondria randomly segregate and assort themselves into the proliferating daughter cells resulting from cell division some daughter cells can receive a very high ratio of mutant mitochondria (mitochondria carrying disease-causing mutations) to normal mitochondria other daughter cells can have a very low ratio of mutant mitochondria (mitochondria with genetic mutations that can cause mitochondrial diseases) to normal mitochondria in order for a disease to occur within a particular cell or tissue (a mitochondrial disease), the ratio of mutant mitochondria to normal mitochondria within a cell or collections of cells needs to exceed a particular cell or threshold in order for this cell or tissue to exhibit a mitochondrial disease

mitosis

mitosis is the phase that occurs once the cell during the G2 phase has gathered and accumulated all of the necessary materials it requires in order for nuclear and cellular division to occur (in order for its nucleus and the cell itself to divide) the M phase of the cell cycle is the phase where the process of cellular division actually occurs, when the cell divides into two separate and distinct and demarcated entities, two genetically identical daughter cells WHAT IS THE PRIMARY PURPOSE OF MITOSIS? why does mitosis occur, what is the primary purpose of this process occurring the primary purpose and function of mitosis is to sort and distribute all of the replicated genetic material within the cell, to sort all of the chromosomes (including the duplicated one) into separate and opposing areas of the cell, so once the cell divides, the genetic material is evenly divided the primary purpose and function of mitosis is to split the one nucleus of the original cell containing all of the genetic information (particularly all of the genetic information including the replicated genetic information) and dividing it into two nuclei, each with equal amounts of genetic information each daughter cell, due to this division of the nucleus into two nuclei, and the division of the genetic material into two equal haves, both have equal complements of chromosomes an example to showcase this during the G2 phase, a cell within this phase will contain 96 sister chromatids, paired together into 46 pairs, 2 sister chromatids per pair forming chromosomes in the mitotic phase, these pairs of sister chromatids are separated and distributed equally to opposing parts of the cell, so that each daughter cell receives an equal number of the right types of chromosomes, 46 chromosomes each when was mitosis first observed? MITOSIS WAS FIRST OBSERVED MICROSCOPICALLY mitosis, this process of mitosis was first observed microscopically in the 1870s this mitotic process was discovered in the 1870s by the German biologist Walter Flemming Walter Flemming was the German biologist that first observed the process of mitosis microscopically in the 1870s WALTER FLEMMING IS THE INDIVIDUAL who coined the term mitosis the term mitosis comes from the Greek word mitos the Greek word mitos means thread Walter Flemming studied the epithelial cells of salamander larvae, and observed these epithelial cells of salamander larvae going through the cell cycle and undergoing mitotic division while observing the cell cycle these salamander larvae epithelial cells were going through, the mitotic division they were undergoing, Walter Flemming noticed that the chromosomes were constructed out of TWO PARALLEL THREADS two parallel threads composed each chromosome he observed that during mitosis, these two parallel threads composing a chromosome separated from one another, and were sorted evenly into the 2 daughter nuclei, from chromosome split to chromosome split (each daughter nucleus received 1 thread of the pair composing a single chromosome) therefore Flemming made the claim and came to the conclusion that the two daughter cells inherited an identical group of threads, a quantity that was comparable and similar to the number of threads found in the original parent cell

mitotic nondisjunction or chromosome loss

mitotic nondisjunction or chromosome loss can produce a patch of tissue with an altered chromosome number mitotic nondisjunction or chromosome loss can produce a patch of tissue with an altered chromosome number mitotic nondisjunction or chromosome loss can produce a patch of tissue with an altered chromosome number abnormalities in chromosome number can occasionally occur after fertilization takes place abnormalities in chromosome number can occasionally occur after fertilization takes place abnormalities in chromosome number can occasionally occur after fertilization takes place in this case, the abnormal event happens during mitosis rather than meiosis, it is mitotic nondisjunction rather than meiotic nondisjunction one possibility is that the sister chromatids separate improperly from one another, so one daughter cell has three copies of a chromosome and the other daughter cell has only one copy of this chromosome one possibility is that the sister chromatids separate improperly from one another so one daughter cell has three copies of a chromosome, and the other daughter cell has only one copy of a chromosome, which will result in unusual gametes, two gametes from the daughter cell resulting from meiosis I contributing to a trisomy in whatever zygote it creates (if it creates this zygote with a normal gamete with a normal amount of genetic material) then there will be an additional two gametes, created from the daughter cell resulting from meiosis containing 1 chromosome only, these haploid cells will both contribute to monosomy in whatever zygote they contribute to the creation of, due to the fact that they are both missing a chromosome that they should have, due to being created from a daughter cell that was missing on pair of sister chromatids that would have separated into two individual chromosome that are now missing from these gametes another possibility is that the SISTER CHROMATIDS COULD SEPARATE DURING ANAPHASE OF MITOSIS another possibility is that sister chromatids could indeed separate during anaphase of mitosis, but one of the chromosomes could be improperly attached to the spindle, so that this chromosome does not migrate to a pole a chromosome will be degraded if it is left outside of the nucleus when the nuclear membrane reforms during telophase II of meiosis II in this case, one of the daughter cells contains two copies of the chromosome rather than the one that it is supposed to have, due to meiotic nondisjunction occurring within the daughter cell that resulted from meiosis I, but meiotic nondisjunction occurring during meiosis 2, the sister chromatids not separating from one another and migrating to opposite poles as they should therefore one of the daughter cells contains two copies of that chromosome, while the other daughter cell resulting from that meiosis I daughter cell containing 1 copy of a chromosome it requires, and missing another chromosome, the other chromosome it requires the first daughter cells containing two copies of one chromosome and one copy of another chromosome will contribute to trisomy the second daughter cell will containing one copy of one chromosome and no copy of another chromosome, and therefore will contribute to monosomy the other two haploid daughter cells resulting from a meiosis I daughter cell will contain normal amounts of genetic material, being haploid however genetic abnormalities can occur after fertilization genetic abnormalities can occur after fertilization, and the organism contains a subset of cells that are genetically different from those of the rest of the organism when genetic abnormalities occur after fertilization, the organism then contains a subset of cells that are genetically different from the rest of the organism this condition is known and designated as genetic mosaicism, where an organism contains a subset of cells that are genetically different from those of the rest of the organism genetic mosaicism is where an organism contains a subset of cells that are genetically different from those of the rest of the organism the size and the location of the mosaic region depends upon the timing and location of the original abnormal event the size and the location of the mosaic region depends on the timing and the location of the original abnormal event if a genetic alteration happens very early in the embryonic development of an organism if a genetic alteration occurs v early in the embryonic development of an organism, the abnormal cell will the precursor for a large section of the organism, the size of the mosaic region all most likely be quite large if the abnormal genetic event, if the genetic alteration occurs v early in the embryonic development of an organism in the most extreme case, an abnormality, a genetic abnormality can take place at the first mitotic division in the most extreme case, an abnormality, a genetic abnormality can occur at the first mitotic division of a zygote, at the very start of the embryonic development an example of this where an abnormality, a genetic abnormality can take place at the commencement at the start of embryonic development is a fertilized drosophila egg that is XX a fertilized drosophila egg that is XX, that has the chromosomal combination XX one of the X chromosomes my be lost during the first mitotic division of this fertilized egg with the XX sex chromosome combination, and that will produce one daughter cell that is XX, and one that is X0, missing one of its X chromosomes, because there is a genetic abnormality that occurs at the first mitotic division that causes one of the cells to lose its x chromosome, flies that are xx develop into females, and flies that are X0 develop into males therefore in this example, one half of the organism becomes female and the other half of the organism becomes male this peculiar and rare individual where half of the organism develops into a female, and the other half of the organism develops into a male is referred to as a bilateral gynandromorph this organism where half of the organism becomes female and half of the organism becomes male is known as a bilateral gynandromorph, and this is all due to during the first mitotic division, one of the resulting daughter cells losing an x chromosome, resulting in a daughter cell that is XX and a daughter cell that is X0, the one that is XX developing into a female, and the one that is X0 developing into a male

monoploids produced in agricultural and genetic research

monoploids that are produced in agricultural and genetic research can be utilized in order to make homozygous and hybrid strains of plants monoploids that are produced in agricultural and genetic research can be utilized in order to make homozygous and hybrid strains monoploids that are produced in agricultural and genetic research can be utilized in order to make homozygous and hybrid strains monoploids that are produced in agricultural and genetic research can be utilized in order to make homozygous and hybrid strains a goal of some plant breeders is to have diploid strains of crop plants that are homozygous for all of their genes one true breeding strain can then be crossed to a different true breeding strain one true breeding strain that is homozygous for all of its genes can be crossed to a different true breeding strain that is also homologous for all of its genes, in order to produce an F1 hybrid that is heterozygous for many genes, due to it resulting from a cross bw two true breeding plants these hybrids that are created as the result of a cross bw two true breeding plants are oftentimes more vigorous than the corresponding homozygous plant strains that they were created from a cross bw this phenomenon is designated as hybrid vigor, or heterosis, where the hybrid being heterozygous for many genes is oftentimes more vigorous than either of the corresponding homozygous strains seed companies often utilize these strategies of breeding together two true breeding plants to create a hybrid in order to produce hybrid seed for many crops such as corn and alfalfa, which can be potentially more vigorous than their corresponding homozygous strains in order to achieve this goal of producing hybrid seeds frommany crops, the seed companies must have homozygous parental strains that can be crossed to one another in order to produce the hybrid seed in order to achieve this goal of producing hybrid seeds for a multitude of crops, the seed companies must have homozygous parental strains that can be crossed to one another in order to produce the hybrid seed one way to obtain the homozygous strains involves inbreeding over many generations one way to obtain these homozygous strains that these seed companies will cross in order to produce hybrid strains involves inbreeding over many generations this production of homozygous strains may be accomplished after several rounds of fertilization, after several rounds of fertilization, the production of a homozygous strain that can be crossed with another to produce an advantageous and more vigorous hybrid strain occurs this is a rather time consuming endeavor there is an alternative to this time consuming endeavor which is the production of monoploids MONOPLOIDS are organisms that have a single set of chromosomes within their somatic cells monoploids are organisms that have a single set of chromosomes within their somatic cells monoploids are organisms that have a single set of chromosomes within their somatic cells and monoploids organisms that have a single set of chromosomes within their somatic cells can be utilized as part of an experimental strategy to develop homozygous diploid strains of plants monoploids are organisms that have a single set of chromosomes, and they can be utilized as part of an experimental strategy to develop homozygous diploid strains of plants monoploids have been utilized order to improve agricultural crops such as wheat, rice, corn, barley, and potato in 1964, Sipra Guha-Mukherjee and Satish Maheshwari developed a method to produce monoploid plants, plants with a single set of chromosomes within their somatic cells, produce these monoploid plants directly from pollen grains there is the experimental technique of anther culture, that has been extensively utilized in order to produce diploid strains of crop plants that are homozygous for all of their genes there is the experimental technique of anther culture that has been extensively utilized in order to produce diploid strains of crop plants that are homozygous for all of their genes this method of anther culture in order to produce diploid strains of crop plants that are homozygous for all of their genes involves alteration bw monoploid (containing a single set of chromosomes within the somatic cells) and diploid (containing two sets of chromosomes within the somatic cells) generations, alteration bw monoploid and diploid generations in order to produce a diploid strains of crop plants that are homozygous for all of their genes the parental plant is diploid but it is not homozygous for all of its genes the anthers from this diploid plant are collected, and the haploid pollen grains are induced to begin their development by a cold shock a cold shock is an abrupt exposure to temperature, and the haploid pollen grains are induced to begin development by cold shock, an abrupt exposure to cold temperature after several weeks, monoploid platelets emerge from tase haploid pollen grains that are taken from the anthers of this diploid plants and induced to develop and grow with a cold shock after several weeks monoploid plantlets, plantlets whose somatic cells contain a single set of chromosomes emerge, and these monoploid plantelets can be grown on agar media in a lab however, due to the presence of deleterious alleles that are recessive, many of these pollens grains may fail to produce viable plantlets due to the presence of deleterious alleles that are recessive despite being induced to develop by a cold shock therefore, anther culture has been described as a monoploid sieve that weeds out individuals that carry deleterious recessive alleles eventually the plantlets that are healthy can be transferred to small pots after the plantlets grow to a reasonable size, a section of the monoploid plant can be treated with colchicine in order to convert it to diploid tissue, to induce a form of polyploidy where a section of the plant is treated with colchicine, inducing nondisjunction, probably complete nondisjunction, resulting in a polyploid diploid in particular cell that will propagate a cutting from this diploid section can then be utilized in order to generate a separate plant this diploid plant is homozygous for all of tis genes because it was produced by the chromosome doubling of a monoploid strain IN CERTAIN ANIMAL SPECIES, monoploids can be produced by experimental treatment that induces the eggs to begin development without fertilization by sperm in particular animal species, monoploids can be produced by experimental treatment that induces the eggs to begin development without being first fertilized by sperm this process is known as parthenogenesis where monoploids, organisms with somatic cells containing a single set of chromosomes are produced by experimental treatments that induce eggs to develop without fertilization by sperm in many cases however, the haploid zygote that is produced by the egg being induced to develop without the fertilization of sperm only develops for a short amount of time before it dies this haploid gamete that develops from an egg being induced to develop prior to sperm fertilization occurring will not live for a long period of time, will not develop after a certain period of time, and will then die nevertheless a short phase of development of this haploid zygote, this haploid embryo resulting from the induced development of an egg prior to the fertilization of the egg with sperm, the induced development of an egg without fertilization by sperm, the haploid embryo resulting from this can be useful to research scientists an example of how it can be useful to research scientists there is the zebrafish, also known as Danio rerio, the zebrafish is a common aquarium fish, and this fish has gained popularity amongst researchers interested in vertebrate development, in the development of verterbrate the haploid egg can be induced to begin development by exposure to sperm rendered biologically inactive by UV radiation the haploid egg of the zebrafish can be induced to develop by th exposure to sperm that are rendered biologically inactive by UV radiation and will not participate in the development of the now haploid embryo resulting from the development of the haploid egg

hypothesis testing

one general type of scientific approaches also known as the SCIENTIFIC METHOD scientists follow and implement a number of outlined steps in order to come to a verifiable, accepted conclusions about the world (this conclusion is given merit due to the procedures followed in order to reach this conclusion) you can prove or disprove a hypothesis by following the scientific method

dominant vs. incompletely dominant

our designation of a trait as dominant or incompletely dominant stems from how closely we look at the trait in the individual if we look as close as we possibly can, we are able to recognize that the heterozygote is not in fact the exact same as the homozygote, even when the heterozygote and homozygote display the same phenotypic expression an example of this is pea shape, studied by Mendel Mendel eventually concluded through his visual observations that the RR and Rr (homozygous dominant and heterozygous dominant) genotypes produced round seeds, while the rr (homozygous recessive) phenotype produced wrinkled seeds the morphology of the wrinkled seed is caused by a large decrease in the amount of starch deposition in the seed this decrease in the amount of starch deposition is caused by a defective r allele, this is probs a loss-of-function mutation when these round and wrinkled seeds are examined under a microscope, we can observe that: the round seeds from heterozygous organisms contain an intermediate amount of starch grains as compared to the number of starch grains found in the seeds of a homozygous dominant organism however this heterozygotes contain just enough starch grains in its seeds in order for the seeds to present as round within the seed, an intermediate amount (around 50 percent) of the functional protein that produces the starch grains is not enough to produce the same number of starch grains produced by the 100% amount of starch producing protein expressed by the homozygous dominant allelic combinations of the homozygous dominant round seeds however due to our unaided eyes, we still view the homozygous dominant and the heterozygous dominant seeds as equal to one another at the level of starch biosynthesis, we can see that the homozygous dominant seed and the heterozygous dominant seed are not equal to one another

pollen grains

pollen grains are formed in the anthers of the plant, and within these pollen grains, male gametes (sperm) are formed

mutant alleles

random mutations occurring within preexisting alleles these are distinct from the more common and prevalent wild-type alleles these random mutations occur and can result in the alteration of phenotypic traits within certain organisms of a population random mutations are more likely to interfere with and disrupt gene function, and therefore mutant alleles (impacted by these random gene mutations) are more likely to lose their ability to express a functional protein (and perhaps instead express a nonfunctional or defective protein) these mutant alleles are rare in natural populations, and tend to be quite often inherited in a recessive fashion

recessive alleles

recessive alleles usually cause a substantial decrease in the expression of a functional protein the analysis of a multitude of human genetic diseases has supported this conclusion and verified it a human genetic disease is usually caused by a mutant allele there are several human genetic diseases where the recessive allele is unable to produce a specific necessary cellular protein in its active form at the right concentration in order to discover which alleles are wild-type and which ones are recessive, molecular genetics researchers have been able to clone genes and distinguish these kinds of alleles from one another the conclusion they have come to through this research is that the recessive allele usually contains a mutation, and this mutation causes a defect in the creation and synthesis of a fully functional protein, rendering it non-functional and fully defective, or partially functional

bacterial dna replication process

replication is initiated by the binding of the DnaA protein to the origin of replication there has been considerable research implemented that has focused upon the origin of replication within Escherichia coli there has been considerable research implemented that has focused upon the origin of replication, the single origin of replication within the bacterial chromosome of Escherichia coli there has been considerable research that has focused and concentrated on the origin of replication within Escherichia coli this origin of replication within the bacteira Escherichia coli, this origin of replication within Escherichia ecoli is named oriC for origin of Chromosomal replication this origin of replication within the bacteria Escherichia coli is known and designated as oriC for origin of Chromosomal replication there are three types of DNA sequences that are found within oriC within the origin of chromosomal replication, the origin of replication within the bacteria Escherichia coli there are three types of DNA sequences that are found within the oriC there are three types of dna that are found within the origin of replication of the bacteria Escherichia coi, three types of dna that are found within the origin of replication of the bacteria Escherichia coli, an origin of replication designated and known as oriC origin of chromosomal replication these three types of dna found within the oric of Escherichia coli are: an AT-rich region DnaA box sequences GATC methylation sites These three types of dna found within the oric of Escherichia coli are an AT rich region, DnaA box sequences, and GATC methylation sites These three types of dna found within the oric of Escherichia coli are an AT rich region, DnaA box sequences, and GATC methylation sites These three types of dna found within the oric of Escherichia coli are an AT rich region, DnaA box sequences, and GATC methylation sites The GATC methylation sites will be discussed later within this chapter, as the GATC methylation sites are concerned with the regulation of replication DNA replication is initiated by the binding of the DnaA proteins to sequences within the origin of replication that are known as DnaA box sequences Dna replication is inititated by the binding of the DnaA proteins to sequences to sequences within the origin of replication that are known as DnaA box sequences Dna replication the process of DNA replication Dna replication the process of dna replication The process of dna replication is initiated byy the binding of DnaA proteins to sequences within the origin known as DnaA box sequences The process of dna replication is initiated by the binding of DnaA proteins to sequences within the origin known as the DnaA box sequences The process of dna replication is initiated by the binding of DnaA proteins to sequences within the origin of replication, sequences within the oric (the origin of chromosomal replication, the origin of replication within the bacteria Escherichia coli) within the dna sequences within the oric designated DnaA box sequences The DnaA box sequences these particular dna sequences that are one of the three types of dna sequences found within the origin of chromosomal replication, the origin of replication within the bacterial chromosome of Escherichia coli, the DnaA box sequences these particular dna sequences serve as recognition sites for the binding of DnaA proteins DnA box sequences these particular dna sequences serve as recognition sites for the binding of DnA proteins DnaA box sequences are dna sequences within the oric within the origin of chromosomal replication within the origin of replication of the bacteria Escherichia coli DnaA box sequences are dna sequences within the oric within the origin of chromosomal replication within the origin of replication of the bacteria DnaA box sequences are dna sequences within the oric within the origin of chromosomal replication within the origin of replication of the bacteria Escherichia coli Dna replication within Escherichia coli is initiated by the binding of DnaA proteins to dna sequences within the origin known as DnaA box sequences Dna replication within Escherichia coli is initiated by the binding of DnaA boxes to dna sequences within the oric, within the origin of chromosomal replication, within the origin of replication of Escherichia coli of the circular, bacterial chromosome/dna Dna replication within bacterial cells, bacterial dna replication is initiated by the binding of proteins designated as DnaA boxes to particular specific dna seqeuneces within the oric within the origin of chromosomal replication (the origin of dna replication within Escherichia coli) designated as DnaA box sequences The DnaA box sequences, one of three types of sequences found within the origin of chromosomal replication, the origin of replication of Escherichia coli, the DnaA box sequences serve as recognition sites for the binding of DnaA proteins When DnaA proteins are in their ATP-bound form, they bind to the five DnA boxes in oric in the origin of chromosomal replication, the origin of replication of Escherichia coli in order to initiate dna replication When DnaA proteins are in their ATP-bound form, when DnaA proteins are bound to ATP, and therefore the DnaA proteins are in their ATP bound form, when the DnaA proteins are in their ATP bound form, they bind to the five DnaA boxes within the oric within the origin of chromosomal replication, the origin of replication of Escherichia coli These DnaA proteins when they are in their ATP-bound form, bind to the 5 DnaA boxes located within the oric within the origin of chromosomal replication, the origin of replication of Escherichia coli DnaA proteins also bind to eahcother in order to form a complex DnaA proteins also bind to eachother in order to form a complex DnaA protiens, in addition to binding to the 5 DnaA boxes within the oric region of the bacterial chromosome of Escherichia coli, the oric, the origin of chromosomal replication, the origin of replication of Escherichia coli, also bind to one another in order to form complex With the aid of other DNA binding proteins, with the aid of other DNA-binding proteins such as HU and IHF, this causes the DNA to bend around the complex of DnaA proteins constructed from the DnaA proteins binding to one another, and this results in the separation of the AT-rich region, another type of DNA sequence located within the oric within the origin of chromosomal replication, the origin of replication of Escherichia coli With the aid the assistance of other DNA binding proteins, other proteins that bind dna such as HU and IHF, with the assistance of the DNA binding proteins such as HU and IHF in addition to the DnaA proteins binding to one another in addition to binding to the 5 DnaA boxes within the oric, the DNA bends around the complex of DnaA proteins formed due to the DnaA proteins binding together into a complex, bends around the complex, and this results in the separation of the AT-rich region Because there are only two hydrogen bonds formed within a base pair consisting of adenine and thymine, bc of the presence of only two hydrogen bonds bw adenine and thymine when they are in a base pair, dna strands are more easily separated at AT-rich regions where the number of hydrogen bonds that need to be broken in order to separate the dna strands is smaller than the number of hydrogen bonds that need to be broken in order to unzip the dna in a region rich with guanine and cytosine, two nitrogenous bases that have 3 hydrogen bonds located bw them, therefore resulting in more hydrogen bonds necessary to break in order to unzip strands of dna that are in guanine and cytosine rich regions following the separation of the AT rich region following the separation of the AT rich region, following the separation of the AT rich region, the DnaA proteins, with the assistance with the help of the DnaC protein, recruit dna helicase proteins to this site following the separation of the AT rich region, following this event, that is due to the formation of the complex of DnaA proteins that conglomerate with one another in addition to binding to the 5 DnaA boxes within the oric, within the origin of chromosomal replication, the origin of replication of Escherichia coli, as well as the assistance and aid of dna binding proteins, proteins that bind to dna, such as HU and IHF, and the resulting event of DNA bending around the conglomeration of DnaA proteins, bending around the complex of DnaA proteins, and therefore resulting in the separation of the AT rich region following the separation of AT rich region that occurs due to the aforementioned events of the DNA bending around the complex of DnaA proteins that conglomerated with one another to form a complex in addition to binding to the 5 DnaA boxes within the oric region, the origin of chromosomal replication, the origin of replication of Escherichia coli, as well as the assistance of dna binding proteins such as HU and IHF, the DnaA proteins along with the assistance of the DnaC protein the DnaA proteins along with the assistance of the DnaC protein recruit DNA helicase proteins to this site where the AT rich region has separated once the AT rich region has separated the DnaA proteins along with the assistance of the DnaC protein recruit DNA helicase proteins to this site where the AT rich region has separated the DnaA proteins along with the assistance of the DnaC the DnaA proteins along with the assistance of the DnaC protein recruit DNA helicase proteins to this site where the AT rich region has separated DnaA proteins along with the assistance of the DnaC protein recruit DNA helicase proteins to this site where the AT rich region has separated Dna helicase is also designated as DnaB protein When a DNA helicase encounters a double stranded region Dna helicase is also designated as DnaB protein Dna helicase is also designated as DnaB protein Dna helicase is also designated as DnaB protein When a dna helicase encounters a double stranded region, when a dna helicase encounters a double stranded region, when it is recruited by the DnaA proteins with the assistance of the DnaC protein when the Dna helicase protein, when the DnaB protein encounters a double stranded region, it breaks the hydrogen bonds bw the two strands, therefore generating two individual and separate strands It breaks the hydrogen bonds bw the two strands therefore generating two individual and separate strands Two dna helicases begin strand separation Two dna helicases are recruited and begin the process of strand separation within the oric region, within the origin of chromosomal replication, within the origin of replication of Escherichia coli Two dna helicases are recruited and begin the process of strand separation within the oric region,a dn they continue to separate the dna strands beyond the oric, beyond the origin of chromosomal replication, beyond the origin of replication of Escherichia coli Two dna helicases are recruited and begin the process of strand separation withint he oric region, within the origin of chromosomal replication, within the origin of replication of Escherichia coli, but also continue strand separation beyond the origin of replication of Escherichia coli These proteins the dna helicase proteins also designated as DnaB proteins utilize the energy provided by the process of ATP hydrolysis in order to catalyze the separation of the double stranded parental/original/template dna These proteins these dna helicase proteins also designated as DnaB proteins utilize the energy provided by the process of ATP hydrolysis in order to catalyze the separation of the double stranded parental/template/original regions These dna helicase proteins also designated as DnaB proteins utilize the energy provided by the process of ATP hydrolysis in order to catalyze the separation of the double stranded parental/template/original dna Within Escherichia coli, DNA helicases bind to single stranded dna and travel along the single stranded dna in the 5 prime to 3 prime direction Within the Escherichia coli dna helicases bind to single stranded dna and travel along the dna in the 5 prime to 3 prime direction Within the Escherichia coli dna helicases bind to single stranded dna and travel along the dna in the 5 prime to 3 prime Within the Escherichia coli dna helicases bind to single stranded dna and travel along the dna in the 5 prime to 3 prime direction Within the Escherichia coli dna helicases bind to single stranded dna and travel along the dna in the 5 prime to 3 prime direction In Escherichia coli dna helicases bind to single stranded dna and travel along the dna in a 5 prime to 3 prime direction in order to keep the replication fork moving in Escherichia coli dna helicases ind to single stranded dna and travel along the dna in a 5 prime to 3 prime direction in order to keep the replication fork moving in Escherichia coli dna helicases bind to single stranded dna and travel along the dna in a 5 prime to 3 prime direction in order to keep the replication fork, where the dna strands are separated where the parental/template/original dna strands are separated from one another and the new daughter strands are being synthesized the action of the dna helicases binding to single stranded dna and moving along the dna in the 5 prime to 3 prime direction in order to keep the replication fork the action of the dna helicase binding to single stranded dna and traveling along the single stranded dna that it binds to in the 5 prime to 3 prime direction in order to keep the replication forks moving (replication fork- recall that this is a region where the two parental/template/original dna strands are separated from one another, and the two new daughter strands are being synthesized alongside these parental/template/original dna strands the action of dna helicases promotes the movement of two replication forks the action of the two dna helicases binding to two different and individual single stranded dna regions, and then moving along the single stranded dna in two separate locations in the 5 prime to 3 prime direction, the actions of the dna helicases promot the movement of two replicatin forks outward from the oric from the origin of chromosomal replication, from the origin of replication of Escherichia coli this movement of two replication forks outward from the oric from the origin of chromosomal replication, the origin of replication of Escherichia coli, the movement of two replication forks outward from the oric initiates the replication of the bacterial chromosome in both directions the initiation of replication of the bacterial chromosome in both directions is designated as bidirectional replication the initiation of replication of the bacterial chromosome in both directions is a process designated as bidirectional replication

gene interactions

researchers have looked at gene interactions by studying the following model organisms: -Escherichia coli (a bacterium) -Saccharomyces cerevisiae (baker's yeast) -Arabidposis thaliana (a model plant) -Drosophila melanogaster (fruit fly) -Caenorhabditis elegans (a nematode worm) -Mus musculus (the laboratory mouse) one of the common methods of research utilized in order to investigation the purpose a gene serves is to intentionally produce loss of function alleles, alleles that cause a loss of function in the gene and therefore a loss of function in the product of that gene

maternal effect and embryogenesis

researchers since the aforementioned initial studies into the details of the maternal effect, now understand that maternal effect genes encode proteins that are integral to the early steps of embryogenesis the first stages of embryogenesis are heavily influenced by proteins coded for by maternal effect genes (therefore maternal effect genes have a substantial influence on embryogenesis, the way that the offspring develops and the morphological, physiological, behavioral traits that it displays) the accumulation and conglomeration of the maternal gene products produced by the nurse cells allows embryogenesis (the development of the zygote) to occur very quickly after fertilization (the egg being fertilized by the sperm) maternal effect genes oftentimes play a role in influencing and impacting: - cell division - cleavage pattern - body axis orientation due to the importance of maternal genes in embryonic development, including cell division, cleavage pattern, and body axis orientation if there are defective alleles in maternal effect genes (that essentially are the sole determinants of the phenotype displayed by their offspring), there will be dramatic effects in the offspring, and oftentimes there will be dire consequences in regards to the phenotypic expression of the offspring (due to a defective allele being one of the sole determinants of the phenotype of the offspring)

conservative, semiconservative, and dispersive models

scientists in the late 1950s had considered three different mechanisms in order to explain the net result of dna replication scientists in the late 1950s had considered three different mechanisms in order to explain the net result of dna replication scientists in the late 1950s had considered three different mechanisms in order to explain the net result of dna replication scientists in the late 1950s had considered three different mechanism in order to explain the net result of dna replication scientists in the late 1950s had considered three different mechniams in order to explain the net result of dna replication scientists in the late 1950s had considered three different mechanisms in order to explain the net result of dna replication scientists in the late 1950s had considered three different mechnaims in order to explain the net result of dna replication these mechanism are showcased in the following section of the textbook the first mechanism to explain the net result of dna replication: the conservative modle the first mechanism proposed to explain the net result of dna replication is designated as a conservative model according to the hypothesis of the conservative model, according to the hypothesis of the conservative model, the first model that is mentioned within the book that is utilized in order to potentially explain the net result of dna replication according to the conservative model, the first introduced and proposed model shown within the book that could potentially explain the net result of dna replication, according to this hypothesis of the conservative modle according to this hypothesis of the conservative model, according to this hypothesis of the conservative model, the original arraignment of parental strands, the original arrangement of the two parental strands during the process of dna replication is completely preserved, and the two newly made newly synthesized daughter strands also remain together following the completion of the process of dna replication according to the hypothesis of the conservative model, according to the hypothesis of the conservative model, both strands of parental dna remain together following the completion of the process of replication both strands of parental dna remain together following the completion of the process of replication both strands of parental dna remain together following the completion of the process of replication both strands of parental dna, both of the strands of parental dna remain together following the completion of the process of dna replication also according to the hypothesis of the conservative model, the original arrangement of the parent strands is completely conserved after replication according to the hypothesis of the conservative model, the arrangement of the parent strands is completely conserved after the completion of the process of dna replication, the arrangment of the parental strands is completely conserved, as the two parental/template strands remain together, remain with one another after the completion of the process of dna replication in addition to this principle of the conservative model, where the positions of the original/parent/template strands of DNA remains the same, they remain together, and the original arrangement of the parental/template strands remains the same following the completion of the process of replication in addition to this principle of the conservative model, the two newly made, newly synthesized daughter strands also remain together following the process of replication in addition to this principle of the conservative model, the two newly made, newly synthesized daughter strands also remain together following the process of dna replication the two newly synthesized, newly created daughter strands of dna also remain together following the completion of the process of dna replication there is a second proposed model, a second hypothesis, a second proposed model to explain the net result of dna replication this model, this second proposed model is a semiconservative model in this mechanism, in this particular model, the semiconservative model, it is proposed that the double stranded dna is half conserved following the replication process the semiconservative model- it is proposed that the double stranded dna is half conserved following the process of replication it is proposed that the double stranded dna is half conserved following the completion of the process of replication in other words, the new made double stranded dna, the newly synthesized and composed double stranded dna, the double helix of the double stranded dna is omposed of one parental strand of dna, and one daughter strand of dna the double stranded dna is half conserved following the replication process the double stranded dna is half conserved following the completion of the replication process, following the completion of the process of dna replication the double stranded dna is half conserved following the completion of the process of dna replication the newly made double stranded dna, the newly made double helix of two strands of dna contains one parental/template/original strand of dna, and one newly synthesized, newly created daughter strand of dna there is a third proposed model, there is a third proposed model, a third proposed hypothesis to explain the net result of dna replication this model is designated as the dispersive model the dispersive model, the third hypothesis proposed in order to explain the net result of dna replication, the dispersive model proposes that segments of parental dna and segments of newly made/newly synthesized dna are interspersed in both strands following the replication process the dispersive model proposes that segmnets of parental dna and newly made dna, segments of the parental dna and the newly made daughter dna are interspersed in both of the intertwined strands following the completion of replication this hypothesis, the dispersive model proposes that segments of the parental dna and segments of the newly synthesized daughter dna are interspersed with one another through the two intertwined strands following the completion of the process of dna replication only the semiconservative model, the hypothesis that the double stranded dna is half conserved following the completion of the process of replication the semiconservative model proposes that the double stranded dna is half conserved after the completion of the process of replication the newly made double stranded dna that arises after the process of replication occurs consists of one parental/template strand, and one newly synthesized/daughter strand only this model, the semiconservate model utilized in order to explain the net result of dna replication is actually correct in 1958, Mathew Meselson and franklin stahl in 1958 matthew Meselson and franklin stahl devised and concoted a method to experimentally distinguish newly synthesized, newly created daughter strands from the original parental/template strand within a double helix, a double helix containing two strands of dna, one being the newly synthesized, newly created daughter strand of dna, and one being the original parental/template strand Matthew Meselson and franklin stahl devised a new method in order to experimentally distinguish newly made, newly synthesized, newly created daughter strands from original, parental, template dna strands Their technique involved the labeling of dna with a heavy isotope of nitrogen Nitrogen is found within the bases composing dna, the element nitrogen is found within the bases of dna, the nitrogenous bases of dna which include adenine, thymine, guanine, and cytosine Nitrogen is found within the bases composing dna Nitrogen occurs in a heavy, 15N form, and a light 14N form Prior to their experiment, they grew Escherichia coli cells in the presence of 15N or many generations Prior to their experiment the aforementioned scientists grew Escherichia coli cells in the presence of 15N, the heavy form of nitrogen for many generatins, for a multitude of generations Prior to their experimentation prior to their implemented experimentation, the aforementioned scientists grew Escherichia coli cells in the presence of 15N, in the presence of the heavy form of nitrogen (recall that nitrogen, which is found within the nitrogenous bases of dna, comes in a heavy form 15N and a light form 14N) The experimenters prior to their experimentation grew Escherichia coli cells in the presence of 15N the heavy type of nitrogen, the heavy form of nitrogen, for a multitude of generations, for many generations This produced a population of cells in which all of the dna within these cells, all of the dna located within these escherichia coli cells that had been grown in the presence of N15 the heavy form of nitrogen for a multidue of generations, all of the dna within these cells was heavy-labeled, labeled with N15 the heavy type of nitrogen The dna within these cells was heavy labeled, the dna within these Escherichia coli cells was labeled with N15 the heavy type of nitrogen, the dna within these cells of Escherichia coli was labeled with N15, the heavy type of nitrogen The dna within these cells was heavy labeled, labled with the heavy type of nitrogen, due to a multitude of generations of the Escherichia coli cells being grown in the presence of the heavy type of nitrogen, the N15 At the start of the experimentation, at the start of the experimentation implemented by the aforementioned scientsits, at the start of the experimentation implemented by the aforementioned scientists, with generation 0, they switched the Escherichia coli cells, they switched the Escherichia coli bacteria to a medium that contained only 14N and then collected samples of cells after various time points They switched the Escherichia coli bacteria to a medium that contained only 14N and then collected samples of cells after various time points They switched the escherichia coli bacteira to a medium that contained only 14N the light type of nitrogen, the light type of nitrogen, and then collected samples of Escherichia coli cells after various time points Under the growth conditions that they employed and implemented Under the growth conditions that they employed and implemented Under the growth conditions that they employed and implemented,, 30 minutes is the amount of time required for one double, or one generation time 30 minutes is the amount of time required for one doubling, or for one generation time 30 minutes is the amount of time required for one doubling or for one generation time 30 minutes is the amount of time required for one doubling or for one generation time in regards to Escherichia coli 30 minutes is the amount of time required for one doubling or for one generation time in regards to Escherichia coli Because the bacteira, the escherichia coli cells, the Escherichia coli cells were doubling within a medium that contained only 14N, the light type of nitrogen, all of the newly made strands were labeled with 14N, with light nitrogen, but all of the original, parental, template strands were labeled with 15N, with heavy nitrogen, as the cells that original parental dna was contained within, resulted from a multitude of generations of Escherichia coli cells propagating and being grown within the presence of heavy nitrogen 15N, which caused the dna the original parental template strands of dna to be labeled with that heavy nitrogen the 15N Thus the original parental template strands and the newly synthesized daughter strands were distinguishable from one another, as all of the newly made dna stands, due to the Escherichia coli cells the Escherichia coli bacteria propagating and doubling within a medium containing only 14N the light nitrogen, are labeled with light nitrogen, 14N, but the original strands the original parental template strands of dna remain in the heavy form, labeled with 15N Meselson and Stahl then analyzed the density of dna by the process of centrifugation Meselson and stahl then analyzed the density of dna by the process of centrifugation Meselson and stahl then analyzed the density of dna by the process of centrifugation Meselson and stahl then analyzed the density of dna by the process of centrifugation Meselson and stahl then analyzed the desnity of dna by the process of centrifugation They utilized a cesium chloride CsCl gradient They utilized a cesium chloride CsCl They utilized a cesium chloride a CsCl gradient They utilized a cesium chloride a CsCl gradient The procedure of gradient centrifugation is described later within this book if both of the dna strands contained 14N the light type of nitrogen if bot of the dna strands contained 14N contained the light type of nitrogen if both of the dna strands contained 14N contained the light type of nitrogen, were labeled with 14N, labeled with the light type of nitrogen, then the dna would have a light density as well as sediment near the top of the tube the dna would have a light density as well as sediment located near the top of the tube if both of the dna strands contained 14N, contained the light type of nitrogen if both of the dna strands contained the light type of nitrogen, contained 14N the light type of nitrogen if both of the dna strands contained the light type of nitrogen, then the dna would have a light density as well as sediment located near the top of the tube if one strand contained 14N and the other strand contained 15N if one strand contained 14N contained the light form of nitrogen the light type of nitrogen, and the other contained 15N the heavy type of nitrogen, then the DNA would be half heavy and have an intermediate density if the dna was half heavy and had an intermediate density, then that would indicate that the DNA would be composed of one strand containing 14N the light type of nitrogen and another strand containing 15N the heavy type of nitrogen, if there were these conditions within the double helix of the dna one strand containing 14N the light type of nitrogen and the other strand containing 15N the heavy strand of nitrogen, then the DNA would be half heavy and have an intermediate density finally if both of the strands contained 15N, if both of the strands contained 15N if both of the strands contained 15N, the DNA would be quite heavy due to both of the dna strands containing 15N the heavy type of nitrogen, and the sediment containing the dna would be closer to the bottom of the centrifuge tube due to the weight of the double helix, the weight of the dna strands where both of them contain 15N the heavy type of nitrogen what are the steps of the procedure perhaps more specified there was an excess of 14N the light type of nitrogen containing compounds that were added to the bacterial cells, to cause all of the newly formed dna all of the newly synthesized dna to contain 14N, to be labeled with 14N the light type of nitrogen the cells were then incubated for various lenghs of time in this particular showcasing of the experiments, the N15 labeled dna the dna labeled with N15 the heavy type of nitrogen that came from the generation of Escherichia coli cells developed from a multitude of generations of Escherichia coli cells being grown in the presence of N15, the heavy type of nitrogen, this is designated in purple and the N14 labeled dna, the dna labeled with N14 the light type of nitrogen, dna resulting from the exposure of escehrichia coli cells to n14 containing compounds that would cause all newly synthesized dna to be labeled with and contain n14, the light type of nitrogen, is designated in blue the cells were then lysed through the utilization of lysozyme and detergent the cells were then lysed through the utilization of lysozyme and detergent the cells were lysed by the addition of lysozyme and detergent the lysozyme and detergent disrupt the bacteria cell wall, and in this particular case, disrupted the bacterial cell wall of the Escherichia coli cells, disrupted the bacterial cell wall of the Escherichia coli cells, and the cell membrane of the escherichia coli cells as well the lysozyme and the detergent disrupted the bacterial cell walls and the cell membranes of the Escherichia coli cells as well then a sample of the lysate was loaded onto a cesium chloride gradient a sample of the lysate was loaded onto a cesium chloride gradient a sample of the lysate was loaded onto a cesium chloride gradient something important to note here in regards to the density of dna something important to not here in regards to the density of dna is that the avg density of dna is around 1.7 g/cm^3, and this density of dna is well isolated from other cellular macromolecules making dna distinguishable by its desnity of 1.7g/cm^3 that is markedly different from the densities of other cellular macromolecules the gradients were then centrifuged, after the lysate was placed on the cesium chloride gradient, after the lysate was placed on the cesium chloride gradient, the gradients were centrifuged until the dna molecules reached their equilibrium densities the gradients were centrifuged until the dna molecules reached their equilibrium densities, their densities at equilibrium the gradients were centrifuged until the dna molecules reached their equilibrium densities dna within the gradient can be observed under a UV light dna within the gradient can be observed under a UV light dna located within the gradient can be observed underneath a UV light dna located within the gradient can be observed underneath a UV light dna located within the gradient can be observed underneath a UV light interpretation of data interpreting the data as seen in the data following figure 11.3, after one round of DNA replication, after one round of DNA replication, propagation, doubling, after one generation, all of the dna sedimented at a density that was half heavy which of the three modules is consistent with this result of all of the dna after one round of replication within the Escherichia coli cells being sedimented at a density that was half heavy, having an intermediate density the semiconservative model aligns most closely with this result of all of the dna resulting from one round of replication of Escherichia coli cells, one generation, one doubling being sedimented at a density that was half heavy, having an intermediate density both the semiconservative model and dispersive model are consistent with the result of the dna being sedimented as half heavy, the dna being sedimented as half heavy, having an intermediate density both the semiconservate model and dispersive model align with this experimental result in contrast, the conservative model predicts two separate dna types, a light type and a heavy type of dna one type of dna being labeled with N14 the light nitrogen and the other type of dna being labeled 15N the heavy type of nitrogen because all of the DNA had sedimented as a single band bc all of the DNA had sedimented as. A single band, this model the conservative model was disproved this model the conservative model was disproved due to all of the dna sedimented as a signle band and therefore it not being possible for there to be two separate dna types, one containing and being labeled with N14 the light type of nitrogen and the other containing and being labeled with N15 the heavy type of nitrogen according to the semiconservative model, the replicated dna would contain one original/parental/template strand of dna (a heavy strand due to this dna coming from the Escherichia coli cells that had been the result of multiple generations of Escherichia coli being exposed to an environment containing N15 the heavy type of nitrogen that it had therefore been labeled with) and one newly made newly synthesized daughter strand (a light strand resulting from the replicated dna that came about due to generation 0 being exposed to N14 containing compounds and therefore containing and being labeled with N14 the light type of nitrogen) according to the semiconsevative model, the replicated dna would contain an original strand (a heavy strand) and a newly made newly synthesized daughter strand (a light strand) likewise in a dispersive modle, all of the DNA should have been half heavy, have an intermediate density after one round of propagation, one generation as well in order to determining whether the semiconservative or the dispersive model was a correct representation of the process that brings about the net result of dna replication, Meselson and stahl had to investigate future generations after conducting approximately two rounds of DNA replication after two rounds of DNA replication had occurred (about 1.9 generations due to about approximately two rounds of DNA repliction), a mixture of light dna and half heavy DNA was observed a mixture of light DNA and half heavy DNA was observed this result was consistent with the semiconservative model of DNA replication this result was consistent with the semiconservative model of DNA replication, because some molecules within the second generation should contain all light dna, labeled with 14N the light type of nitrogen, and some DNA molecules should be half heavy with an intermediate desnity the dispersive model predicts that after 2 generations, after 2 rounds of dna replication, the heavy nitrogen would be evenly dispersed among the four strands resulting from the two implemented and completed rounds of DNA replication, each resulting dna strand containing ¼ heavy nitrogen and ¾ light nitrogen however this result was not obtained when the dna strands resulting from two rounds of DNA replication were observed instead the results of the Meselson and the stahl experiment provided compelling evidence due to their initial and continued observations in favor of the semiconservative model for dna replication, where after one round of replication, the dna sediment is half heavy, and at an intermediate weight due to presence of light and heavy dna mixed with one another, the resulting dna strand containing one parental/template/original strand containing and being labeled with 15N the heavy type of nitrogen, and containing one newly synthesized, newly created daughter strand containing and being labeled with 14N, the light type of nitrogen, as well as observations made after the completion of 2 rounds of replication, where some dna molecules within the second generation contain only light dna, contain only 14N the light type of nitrogen, while other dna molecules within the second generation maintain and contain a half heavy conformation, an intermediate density consistent with the results showcased after the completion of the first round of dna replication

chromosomes further compaction past the 30 nm fiber

so far, we have examined two mechanisms that are responsible for the compaction of DNA these two mechanisms include the following: THE WRAPPING OF DNA within nucleosomes and the arrangement of nucleosomes to form a 30 nm fiber the first mechanism is THE WRAPPING OF DNA OF THE DOUBLE STRANDED HELICAL DNA MOLECULE AROUND NUCLEOSOMES IN ORDER TO SUBSTANTIALLY SOMEWHAT COMPACT THE DNA the second mechanism is the arrangement of nucleosomes that results in further compaction of DNA the second mechanism is the particular arrangement of nucleosomes that results in the further compaction of DNA occurring, this arrangement of nucleosomes in a particular manner results in the further compaction of DNA into the conformation of a 30nm fiber taken together, these two events, the wrapping of the double stranded helical DNA molecule that occurs within a nucleosome (where a double stranded helical DNA molecule wraps itself around an octamer of histones in order to properly take the first step in further compactioN) as well as the arrangement of these created nucleosomes in a particular manner resulting in even further compaction together SHORTEN THE LENGTH OF DNA about 50 FOLD these two DNA compaction mechanisms together result in the shortening of the DNA 50 FOLD together these two mechanism v dramatically and substantially contribute to the necessary compaction of DNA there is a third level of compaction THERE IS A THIRD LEVEL OF COMPACTION this third level of compaction involves INTERACTIONS OCCURRING BW the 30 NM FIBERS AND A FILAMENTOUS NETWORK OF PROTEINS WITHIN THE NUCLEUS there is a third level of compaction that occurs after the previous 2 mechanisms of compactions, the wrapping of DNA within nucleosomes (the wrapping of the double stranded, helical dna molecule around an octamer of histones) and the arrangement of nucleosomes in order to further the compaction of DNA (these two mechanism, you should recall contribute to the compaction of the DNA 50 FOLD) the third level of compaction INVOLVES INTERACTIONS BW the 30 NM FIBERS AND A FILAMENTOUS NETWORK OF PROTEINS WITHIN THE NUCLEUS DESIGNATED AS THE NUCLEAR MATRIX the third level of compaction involves interactions occurring bw the 30 nm fibers created by the particular arrangement of nucleosomes, and a filamentous (composed of filaments) network of proteins within the nucleus this filamentous network of proteins within the nucleus is designated and known as the nuclear matrix the interactions bw the 30 nm fibers and the filamentous network of proteins found within the nucleus known as the nuclear matrix results in further compaction of DNA THE NUCLEAR MATRIX CONSISTS OF TWO PARTS the nuclear matrix is composed of 2 parts, it has 2 parts that compose it the nuclear lamina is a COLLECTION OF FIBERS the nuclear lamina is a COLLECTION OF FIBERS and is one of the components of the nuclear matrix one of the components of the nuclear matrix is the nuclear lamina the nuclear lamina is one of the components of the nuclear matrix, and the nuclear lamina is a COLLECTION OF FIBERS that line the inner nuclear membrane the nuclear lamina is a collection of fibers that lines the INNER NUCLEAR MEMBRANE these fibers composing the nuclear lamina that line the inner nuclear membrane are composed of INTERMEDIATE FILAMENT PROTEINS the fibers composing the nuclear lamina that line the inner nuclear membrane are composed of INTERMEDIATE FILAMENT PROTEINS the nuclear lamina is a collection of proteins lining the inner nuclear membrane, and these proteins lining the inner nuclear membrane are composed of INTERMEDIATE FILAMENT PROTEINS the second portion of the nuclear matrix besides the nuclear lamina is the INTERNAL NUCLEAR MATRIX the internal nuclear matrix is CONNECTED TO THE NUCLEAR LAMINA the internal nuclear matrix is CONNECTED TO THE NUCLEAR LAMINA the internal nuclear matrix is connected to the nuclear lamina and FILLS THE INTERIOR OF THE NUCLEUS the INTERNAL NUCLEAR MATRIX is the second component of the nuclear matrix that is attached to the nuclear lamina and fills the internal cavity of the nucleus the structure and function of the internal nuclear matrix remain controversial and debated over IT IS HYPOTHESIZED that the structure of the internal nuclear matrix is AN INTRICATE FINE NETEWORK OF IRREGULAR PROTEIN FIBERS PLUS MANY OTHER PROTEINS THAT BIND TO THESE IRREGULAR PROTEIN FIBERS the hypothesized structure of the internal nuclear matrix is AN INTRICATE FINE NETWORK OF irregular protein fibers, in addition to many other proteins that bind themselves to these irregular protein fibers when the chromatin is extracted from the nucleus, the INTERNAL NUCLEAR MATRIX MAY REMAIN INTACT even when the chromatin is extracted from the nucleus, the internal nuclear matrix may remain completely intact and not be impacted or broken by the extraction of chromatin from the nucleus, which the inner nuclear matrix fills however the MATRIX SHOULD NOT BE CONSIDERED A STATIC STRUCTURE the nuclear matrix is not a static structure at all THE NUCLEAR MATRIX is NOT A STATIC STRUCTURE previously implemented research done on the nuclear matrix has show that the PROTEIN COMPOSITION OF THE INTERNAL NUCLEAR MATRIX is V DYNAMIC and complex it is believed due to previously implemented research done on the nuclear matrix, that the protein composition of the inner nuclear matrix, 1 of the 2 components of the nuclear matrix is v dynamic and complex (though the inner nuclear matrix may remain intact even when chromatin is extracted from the nucleus) the protein composition of the inner nuclear matrix is v dynamic and complex, it varies depending on the species one is looking at this protein composition of the inner nuclear matrix depends upon the SPECIES CELL TYPE ENVIRONMENTAL CONDITIONS the complexity of the inner nuclear matrix has made it difficult to propose comprehensive and verifiable models of the inner nuclear matrix and its complex, dynamic protein composition that changes as you move from species to species, from cell type to cell type, and shift environmental conditions the proteins of the nuclear matrix ARE INVOLVED IN COMPACTING THE DNA THE PROTEINS OF THE NUCLEAR MATRIX< THE PROTEINS COMPOSING THE NUCLEAR MATRIX ARE INVOLVED IN COMPACTING THE DNA how do these proteins of the nuclear matrix compact the DNA? these proteins of the nuclear matrix accomplish compacting the DNA in the following way

gene expression in spite of inactivated X chromosome

some genes on the inactivated chromosome still express themselves despite the X chromosome they are present on being inactivated these genes that still express themselves despite the chromosome they are on being inactivated are said to have escaped the effects of X-inactivation that would have impacted them an example of a gene that is expressed on an inactivated X chromosome is Xist this gene, despite being present on a highly compacted and condensed Barr body, still expresses itself within the human species, up to a quarter of X-linked genes may be expressed on the inactivated X chromosome Barr body (they will escape the inactivation effect to some degree, but all the other genes on that inactivated X chromosome will be impacted by inactivation and not express themselves a lot of the genes that avoid the process of inactivation to some degree on an inactivated X chromosome are found in clusters, mini conglomerations of genes that escape the effects of inactivation and are not inactivated despite being on an inactivated X chromosome Barr body and express themselves some of the genes that express themselves despite being on an inactivated X chromosome (thus avoiding the effects of inactivation) including pseudoautosomal genes that follow a pattern of autosomal inheritance despite being found on the sex chromosomes these are genes that are present in areas of homology bw the X chromosome and the Y chromosome, and therefore within males, the autosomal pattern of inheritance is followed, due to the presence of an allele for that gene being found on both the X and Y chromosome these genes, within females, are expressed with an allele present for each gene on both the active and inactive X chromosome Barr body, these genes avoid x inactivation dosage compensation is not considered a required process for X-linked pseudoautosomal genes (genes that follow an autosomal pattern of inheritance) due to the fact that alleles for these genes (to put together the appropriate allelic combination) are located on both the X and Y chromosomes, so therefore males and females have the same level of gene expression for these X-linked pseudoautosomal genes that follow an autosomal pattern of inheritance, and compensation in order to make the levels of gene expressions in both males and females equal is not necessary, because they already are how in the world are genes on inactivated X chromosome Barr bodies? if there is an X chromosome, and it is inactivated, then how are the genes on this inactivated, compacted, condensed X chromosome able to still express themselves? the mechanism is not fully understood, but it is thought that clusters/conglomerations of genes packed together that express themselves (recall that the genes that express themselves on inactivated X chromosomes tend to be found in clusters) are clustered and gathered in a region on the X chromosome where the DNA isn't quite as compacted, and therefore it can be transcribed, and the genes encoded by this slightly less compacted DNA can be expressed on an otherwise inactive X chromosome

the genetic composition of various kinds of mitochondria and chloroplasts

species within the species Tetrahymena, the organelle within their cells is a mitochondrion, and it contains 1 nuclei with a total of 6-8 chromosomes within the species of mouse, the organelle within their cells is a mitochondrion, and the mitochondrion contains 1-3 nucleoids, and a total of 5-6 chromosomes within the species Chalmydomonas, the organelle within their cells is a chloroplast, and within this chloroplast there are 5-6 nucleoids and around 80 chromosomes total within the species euglena, the organelles within them are chloroplasts, and within the chloroplast there are 20-34 nulceoids, and a total of 100-300 chromosomes per chloroplast within the species of higher plants, the organelles within their cells are chloroplasts, and within a chloroplast, there are 12-25 nucleoids and about 60 chromosomes total within each chloroplast the above demonstrates that as you change species, the number of nucleoids within an organelle, as well as the number of chromosomes contained in total within that organelle, vary the sizes of mitochondrial and chloroplast genomes also vary as you move from species to species (you will find the numbers for their genomes, the totality of their genetic material, changing dramatically as you shift from one distinct species to another) within the sizes of mitochondrial chromosomes, there is a 400 fold variation within animal species, the mitochondrial genomes tend to be fairly insubstantial and small within fungi and protists, their mitochondrial genomes tend to be intermediate, substantial but not too much so within plants, particularly looking at plant cells, their mitochondrial genomes tend to be fairly large and substantial when looking at algae and plants, substantial and dramatic variation can be found in the sizes of their chloroplast genomes as you move from plant to plant and algae to algae and plant to algae, you will find dramatic differences in the sizes of their chloroplast genomes

the inheritance of chloroplasts

specifically, we are looking at the inheritance of chloroplasts that are found in eukaryotic species particularly eukaryotic species that are capable of photosynthesis the main eukaryotic species that are capable of photosynthesis are algae and plants let's take a look specifically at the unicellular alga Chalmydomonas reinhardtii this unicellular alga is used as a model organism, and it is used as a model organism in order to investigate the inheritance of chloroplasts the organism, the unicellular alga Chalmydomonas reinhardtii contains a single chloroplast this single chloroplast contained within the unicellular alga Chalmydomonas reinhardtii occupies approximately 40 percent of the cell volume chloroplast inheritance was initially studied by Ruth Sager Ruth Sager identified a mutant strain of Chlamydomonas reinhardtii this mutant strain of Chlamydomonas reinhardtii is resistant to the antibiotic streptomycin (sm^r), it has this gene sm^r coding for its resistance to the antibiotic streptomycin by comparison the majority of strains of Chalmydomonas reinhardtii are susceptible to being killed by the antibiotic streptomycin- it has this gene sm^s coding for its susceptibility to the antibiotic streptomycin) Ruth Sager implemented a variety of crosses in order to determine the inheritance pattern of the sm^r gene that causes the therefore mutant strain of Chalmydomonas reinhardtii to be resistant to the antibiotic streptomycin during the process of mating (embryogenesis), there are two haploid cells that join in order to create a diploid cell this diploid cell created by the two haploid gamete cells undergoes meiosis in order to form 4 haploid cells Chlamydomonas is also an organism that can be found in two mating types, designated as mt+ and mt- it is similar to yeast in this manner, which is another organism that is found in two different mating types the mating type that a Chlamydomonas reinhardtii organism is is due to the phenomenon of nuclear inheritance (the phenemenon of nuclear inheritance is what influences the mating type of a Chlamydomonas reinhardtii organism) mating type also segregates in a 1:1 ratio, 1:1 manner through the implementation of various crosses by Ruth Sager and her colleagues, it was discovered that the smr gene coding for the mutant strain of Chlamydomonas reinhardtii to be resistant to the antibiotic streptomycin, is inherited from the mating type mt+ parent, and this gene is not inherited from the mating type mt- parent therefore, due to this type of inheritance, it was determined that the smr gene that codes for the mutant strain of Chalmydomonas reinhardtii to be resistant to the antibiotic streptomycin is not inherited according to established Mendelian law the pattern that they found in their crosses occurred due to the fact that only the mt+ mating type parents transmit chloroplast to their daughter cells, and due to the fact that the smr gene coding for resistance to the antibiotic streptomycin is located within the chloroplast genome, only the mt+ mating type parent is able to pass this gene on to the daughter cells

P values within the chi square table

the P values listed in the chi square table allow us to determine the likelihood that the amount of variation indicated by a given chi square value is simply due to random chance, not bc the hypothesis isn't viable certain values are expected to occur 95% of the time when a hypothesis is accurate this means that 95/100 times we would expect that only random chance would contribute to an observed deviation bw the experimental and hypothetical data that is equal to that value low chi square value- it indicates a high probability that any deviations observed are due to random chance chi square values equal to or greater than 3.841 (utilizing this as a given number), that means that these values are expected to occur less than 5 percent of the time due to random sampling error, the culprit is probably the experiment itself high chi square value- the experimenter must suggest to themselves that their hypothesis may be incorrect, bc this value is most likely not due to random sampling error, the deviation cannot be accounted for by random sampling error you should reject the null hypothesis if the chi square value you get results in a less than 5 percent probability for the accountability of random sampling error, or if it is less than 1 percent probability a hypothesis still could potentially be correct despite the probability of accountability of random sampling error being bw 5 and 1 percent at the same time, it could also be incorrect, so you have to make a conscious choice calculated chi square value in the example is 1.06

gene knockout

the abolishment of gene function that is done and implemented by creating an organism that is homozygous for a loss-of-function allele for that gene, there are two loss of function alleles together that homozygous recessively code for the loss of function of that gene the gene has therefore been knocked out gene knockouts are useful, bc you can utilize them in order to understand the role a gene plays in affecting and manipulating the structure and/or function of cells, or understand the role a gene plays in over influencing the expression of a particular phenotypic trait an example of a gene knockout is a researcher knocking out a specific gene in a mouse in order to determine its function if the resulting mouse was unable to hear, the researcher would presume that the function of the gene they knocked out is to allow the mouse to hear the function of the gene is probably the promotion of the formation of mouse ear structures that will allow the mouse to hear through all of the experiments they have done researching with gene knockouts, there are a lot of gene knockouts that have no evident effect on the phenotype of the organism at the cellular or organismal level, one cannot see a difference in the organism prior and after the gene knockout in order to further explore this phenomenon, researchers would knock out two or more genes the individual gene knockouts would not have any effect on the phenotype of the organism, but the accumulation of gene knockouts would cause a phenotypic change

age of onset

the age when symptoms of genetic diseases appear in an affected individual affected individual's with Huntington's disease usually experience the onset of symptoms bw 30 and 50 years of age

renaturation

the approach of renaturation has helped us to understand genome complexity renaturation studies have assisted researchers in understanding the complexity of the genome these kinds of renaturation experiments were first carried out by Roy Britten and David Kohne in 1968 THESE TYPES OF RENATURATION EXPERIMENTS WERE FIRST CARRIED OUT BY ROY BRITTEN AND DAVID KOHNE in 1968 in a renaturation study (including the renaturation studies that these aforementioned individuals roy Britten and David kohne carried out and implemented in 1968), the DNA IS BROKEN UP INTO PIECES CONTAINING SEVERAL HUNDRED BASE PAIRS the DNA IS BROKEN UP INTO PIECES CONTAINING SEVERAL HUNDRED BASE PAIRS in a renaturation study recall that a renaturation study approach, the implementation of renaturation has proven extremely useful and helpful in understanding the complexity of the genome, the complexity contained within any given genome, renaturation implementation has helped us to better understand this renaturation experiments were initially varied out and implemented by Roy Britten and David Kohne in 1968 in a renaturation study, the following steps are implemented: the DNA IS BROKEN UP INTO PIECES CONTAINING SEVERAL HUNDRED BASE PAIRS EACH the dna is broken up into individual pieces containing several hundred base pairs each each individual piece that the dna is broken up into contain several hundred base pairs each then the double stranded dna is denatured another term for denatured in regards to dna is separated, the two intertwined strands composing dna are separated into SINGLE STRANDED PIECES how are they separated into single stranded pieces? the two intertwined pieces of DNA are separated into single stranded pieces by heat treatment through heat treatment, DNA denaturation occurs, and the two intertwined strands of dna separate into 2 distinct pieces when the temperature is lowered after the heat treatment, the pieces of DNA THAT ARE COMPLEMENTARY TO ONE ANOTHER, they would fit well together as their base pairs would match up, can reassociate the pieces of DNA that were denatured but are complementary to one another, containing bases that all respectively come together to form base pairs, can reassociate with one another when the temperature is lowered these complementary individual and independent entities of DNA strands are able to, in lower temperatures, reassociate, reunite with one another in order to form double stranded molecules, they will reform the double stranded molecules they composed prior to heat treatment and denaturation the rate of renaturation of COMPLEMENTARY DNA STRANDS provides a method by which one can DISTINGUISH BW UNIQUE MODERATELY REPETITIVE AND HIGHLY REPETITIVE SEQUENCES the rate of renaturation of complementary DNA strands provides a method by which one can distinguish bw distinct unique, moderately repetitive, and highly repetitive DNA sequence for a given category of DNA sequences (whether it be unique, moderately repetitive, highly repetitive) the rate of RENATURATION depends on the concentration of ITS COMPLEMENTARY PARTNER the renaturation rate of particular sequences of DNA is dependent upon the concentration of its complementary partner HIGHLY REPETITIVE SEQUENCES RENATURE MUCH FASTER bc many copies of the complementary sequences are present HIGHLY REPETITIVE SEQUENCES RENATURE MUCH FASTER bc many copies of the complementary sequences are present there are many copies of the complementary DNA sequence pairs with highly repetitive DNA, therefore the concentration of these DNA sequence complementary partners is high, and therefore the rate of renaturation will be quite quick in contrast to highly repetitive sequences, when we are looking at unique sequences, such as those found within most genes (genes are unique and distinct from one another most of the time, and are encoded therefore by unique and distinct, non repetitive DNA sequences) these unique sequences of DNA will TAKE LONGER TO RENATURE bc there will be fewer of them amongst the DNA complementary partners, therefore a lower concentration of the DNA complementary partners, and therefore a slower rate of renaturation the renaturation of TWO DNA STRANDS the renaturation of TWO DNA strands is a bimolecular reaction this bimolecular reaction involves THE COLLISION OF TWO COMPLEMENTARY DNA STRANDS a bimolecular reaction is designated as a reaction where the collision of 2 reactants takes place in this case, the bimolecular reaction term being used to designated the renaturation of dna is describing the process of dna renaturation as a collision taking place bw two individual dna strands the rate of renaturation is proportional to the product of the concentrations of both strands THE RATE OF DNA RENATURATION IS PROPORTIONAL TO THE PRODUCT OF THE CONCENTRATIONS OF BOTH STRANDS the rate of DNA renaturation is proportional to the concentration of both strands multiplied together for example, if C is designated as the concentration of a single stranded individual DNA, then for any DNA that is derived from a DOUBLE STRANDED FRAGMENT the concentration of a single DNA strand composing this double stranded fragment will be designated as C1, and this concentration of one of the two DNA segments composing the double stranded fragment of DNA, C1 will be equal to the concentration of its complementary partner the other strand of DNA composing this double stranded fragment, its concentration being designated as C2 C=C1=C2 they are all equal to one another therefore the rate of renaturation is represented by the SECOND ORDER EQUATION -dC/dt= kC^2 this equation presenting us with the calculation for rate of renaturation is A SECOND ORDER EQUATION it is designated as a second order equation bc the rate of renaturation is dependent upon the concentration of BOTH REACTANTS-C1 and C2 in this case, the product is simplified from C1 times C2 to C^2, bc C1=C2 what does this equation say? this equation says that a CHANGE IN CONCENTRATION OF A SINGLE STRAND A CHANGE IN THE CONCENTRATION OF A SINGLE STRAND COMPOSING A DOUBLE STRANDED FRAGMENT with respect to time t, this is equal to a rate constant (k) multiplied by the concentration of a single stranded molecule composing a double stranded fragment squared this above equation can be integrated in ORDER TO DETERMINE HOW THE CONCENTRATION OF THE SINGLE STRANDED DNA MOLECULE COMPOSING A DOUBLE STRANDED FRAGMENT CHANGES FROM TIME 0 to A LATER DOCUMENTED TIME the above equation, where the change in concentration of a single strand composing a double stranded molecule fragment with respect to time t is equal to a rate constant (k) multiplied by the concentration of a single stranded molecule composing a double stranded DNA fragment squared this above equation can be integrated in order to determine how in the world the concentration of a single stranded DNA changes from the initial time zero, to a later particular specified time this equation is designated as: C/C0= 1/(1+k2C0t) in this equation: C= the concentration of a single stranded DNA at a later time, designated as t C0= the concentration of a single stranded DNA at time zero k2= the second order rate constant for renaturation, the rate constant for this integrated second order equation detailing the calculations of the renaturation rate of DNA strands looking at C/C0 is the fraction of DNA that is still in the single stranded form after a particular period of time has passed C/C0 represents the amount of single stranded dna left over that has not yet renatured that is present after a particular amount of time if C/C) equals 0.4 after a particular period of time, that means that 40 percent of the DNA is STILL IN THE SINGLE STRANDED FORM, this is the amount of single stranded dna left over that has not yet renatured this figure also means that 60 PERCENT OF THE DNA HAS INDEED RENATURED INTO THE DOUBLE STRANDED FORM OF DNA a renaturation experiment can showcase and provide researchers who implement these renaturation experiments with QUANTITATIVE INFORMATION ABOUT THE COMPLEXITY OF DNA sequences within chromosomal DNA the implementation of a renaturation experiment can provide those who implement it with quantitative data pertaining to the complexity of the genome, the complexity of the DNA sequences found within the chromosomal dna (as they are able to determine the complexity of these DNA sequences through understanding the numbers of uniquely repetitive, moderately repetitive, and highly repetitive sequences as the rates of renaturation for these types of sequences are markedly different) look at the experiment showcased and presented within the textbook IN THE EXPERIMENT SHOWN IN FIGUE 10.13b HUMAN DNA WAS SHEARED INTO SMALL PIECES HUMAN DNA WAS SHEARED INTO SMALL PIECES each of these pieces was about 600bp in length THIS DNA WAS THEN SUBJECTED TO HEAT human dna was sheared into small pieces each piece consisting of 600 base pairs the dna was then subjected to heat the dna was then allowed to renature at a lower temperature THE RATE OF RENATURATION FOR THE DNA PIECES IS REPRESENTED BY A PLOT OF C/C0 which represents the remaining amount of single stranded dna that is left after a certain period of time, remaining single stranded dna that has not yet renatured into double stranded DNA this is plotted against C0t, the initial amount of single stranded dna at time zero multiplied by time t this is called a Cot curve THE TERM COT refers to the DNA concentration (C0) multiplied by the amount of incubation time, the amount of time that the single stranded DNA is exposed to heat and incubated in order to renature a fair amount of the DNA RENATURES VERY RAPIDLY this is the highly repetitive dna, due to the high concentration of complementary single strand sequences that are highly repetitive, these highly repetitive sequences renature quite quickly some of the DNA reassociates and renatures into double stranded dna at a medium rate a moderate rate the remaining DNA renatures and reassociates fairly slowly due to the give data, the relative amounts of highly repetitive, moderately repetitive, and unique DNA sequences amongst the single stranded rna can be determined as shown in the above figure 10.13b about 40 percent of the human DNA fragments are unique DNA sequences that renature slowly, and are probably unique to very lowly repetitive dna sequences

probability

the chance that an event will occur in the future, the likelihood of something happening probability = the number of times an event occurs/the total number of possible events the accuracy of a probability prediction depends on the size of the sample, the number of times an experiment is replicated or a cross is done in order to fully understand the ratio

chromosomal DNA in living bacteria conformation

the chromosomal DNA found in living bacteria is NEGATIVELY SUPERCOILED the chromosomal DNA found in living bacteria is negatively supercoiled in the chromosome of a specific type of bacteria, E. coli, one negative supercoil occurs per 40 TURNS OF THE DOULB HELIX one negative supercoil occurs per 40 TURNS OF THE DOUBLE HELIX in the chromosomal DNA of the bacteria e coli what are the consequences of negative supercoiling? there are many consequences to negative supercoiling THE SUPERCOILING OF CHROMOSOMAL DNA INCREASES COMPACTION GREATLY the supercoiling of DNA makes it far more compact, therefore negative supercoiling has the same particular effect of making the DNA far more compact and causing the chromosomal DNA to be able to fit inside of a given bacterial cell the size of the bacterial chromosome is decreased due to the negative supercoiling of DNA that occurs due to the negative supercoiling of DNA that occurs, the size of the bacterial chromosome decreases, allowing the entirety of the bacterial chromosome and all of its genetic material to fit inside of the given bacterial cell another consequence of negative supercoiling another consequence of negative supercoiling (recall that right now we are particularly referring to the negative supercoiling of bacterial chromosomes, the negative supercoiling of bacterial chromosomal dna) is that it affects DNA function negative supercoiling has an impact on DNA function how does negative supercoiling have an impact and affect DNA function? negative supercoiling is due to an underwinding force occurring on the DNA an underwinding force on the DNA, a force being exerted on the DNA that is in the opposite conformation of the conformation of the DNA will cause underwinding to occur negative supercoiling, a result of underwinding of DNA occurring, will cause TENSION OF THE DNA STRANDS this tension occurring on the DNA strands caused by the negative supercoiling of the DNA caused by the underwinding of the DNA may be relieved and released due to DNA STRAND SEPARATION DNA strand separation may occur in order to relieve the tension that occurs on the DNA due to negative supercoiling that comes from the underwinding of DNA occurring (recall that underwinding specifically of DNA occurs when there is a turn that is the opposite direction of the conformation of the DNA, such as a left handed tun occurring on DNA with a right handed conformation, in this scenario, underwinding would occur) DNA STRAND SEPARATION MAY OCCUR the majority of the bacterial chromosomal DNA is NEGATIVELY SUPERCOILED AND THEREFORE HIGHLY COMPACTED, the sheer force of negative supercoiling and the underwinding that it stems from can cause DNA strand separation to occur in small particular regions of the bacterial chromosome, negative supercoiling and the underwinding that it stems from can cause DNA separation to occur, and when DNA separation occurs, ACTIVITIES SUCH AS REPLICATION AND TRANSCRIPTION occur, these are genetic activities that require the separation of DNA strands, and these activities occur in particular small regions of bacterial chromosomes, due to the negative supercoiling sometimes causing DNA strand separation how does bacteria become supercoiled? how in the world does bacteria become supercoiled? how does it undergo supercoiling? in 1976, Martin Gellert and his colleagues discovered the enzyme DNA GYRASE in 1976, Martin Gellert and his colleagues discovered the enzyme DNA GYRASE Martin Gellert and his colleagues discovered the enzyme DNA GYRASE THE DNA GYRASE ENZYME CONTAINS FOUR SUBUNITS the dna gyrase enzyme contains four subunits including two A and two B subunits the dna gyrase enzyme contains four subunits these four subunits composing and constituting the DNA GYRASE ENZYME ARE 2 a subunits and 2 b subunits THE ENZYME DNA GYRASE IS ALSO DESIGNATED AS TOPOISOMERASE II the enzyme dna gyrase/topoisomerase II is responsible for introducing NEGATIVE SUPERCOILS or RELAXING POSITIVE SUPERCOILS the dna gyrase/topoisomerase ii enzyme is responsible for introducing negative supercoils or relaxing positive supercoils the dna gyrase/topoisomerase ii enzyme is responsible for introducing negative supercoils or relaxing positive supercoils the dna gyrase/topoisomerase ii enzyme is responsible for introducing negative supercoils into the dna or relaxing positive supercoils already present within the dna recall that the dna gyrase/topoisomerase enzyme ii consists of 2 A subunits and 2 B subunits the dna gyrase/topoisomerase ii enzyme is able to introduce negative supercoils and relax positive supercoils through the utilization of ATP the dna gyrase/topoisomerase ii enzyme utilizes ATP in order to introduce negative supercoiling or relax positive supercoils already present in the DNA utilizes energy from ATP in order to carry out these processes (specific to DNA gyrase/topoisomerase II) where it creates negative supercoils within the DNA or relaxes positive supercoils IN ORDER TO AlTER THE SUPERCOILING OF DNA, DNA GYRASE/TOPOISOMERASE II HAS TWO SETS OF JAWS these two sets of jaws that dna gyrase/topoisomerase II is composed, these two sets of jaws that dna gyrase/topoisomerase ii has allows this enzyme to be able to grab onto, to be able to latch onto two regions of DNA these two sets of jaws that dna gyrase/topoisomerase II has allows this enzyme to be able to latch onto two regions of DNA ONE OF THE DNA REGIONS that the dna gyrase/topoisomerase ii enzyme is able to latch onto to is grabbed BY THE LOWERS JAWS this segment, this region of DNA grabbed by the lower jaws is then WRAPPED IN A RIGHT HANDED DIRECTION AROUND THE TWO A SUBUNITS this segment of DNA grabbed onto latched onto by the lower jaws of the dna gyrase/topoisomerase ii is wrapped in a right handed direction around the two A subunits the segment/region of DNA grabbed/latched onto by the lower jaws of the DNA gyrase/topoisomerase ii is wrapped in a right handed direction around the two A subunits the upper jaws of the dna gyrase/topoisomerase II clamp onto a different distinct and independent region/entity of DNA the DNA in the lower jaws is then cut in both strands both strands of DNA in the lower jaws is then cut recall that the lower jaws latched onto a particular strand of DNA and then was wound around the 2 A subunits, now it is cut in both strands the other region of DNA that was latched onto by the upper jaws is released from the upper jaws, and this DNA released from the upper jaws passes through the double stranded break that has occurred in the lower strand of DNA that was latched onto and grabbed onto by the lower jaws of DNA gyrase/topoisomerase II, wrapped around the 2 A subunits, and then cut in both strands what is the net result of these above processes that have just occur to two regions of DNA in the dna gyrase/topoisomerase II enzyme? two NEGATIVE SUPERCOILS HAVE NOW BEEN INTRODUCED INTO THE DNA MOLECULE 2 NEGATIVE SUPERCOILS HAVE BEEN INTRODUCED INTO THE DNA MOLECULE 2 NEGATIVE SUPERCOILS HAVE BEEN INTRODUCED INTO THE DNA MOLECULE DUE TO THE FUNCTIONING OF THE DNA GYRASE/TOPOISOMERASE II ENZYME the DNA gyrase in bacteria and topoisomerase II in eukaryotes can untangle DNA molecules DNA GYRASE IN BACTERIA TOPOISOMERASE II IN EUKARYOTES both are responsible in their respective worlds, DNA gyrase for bacterial cells, and topoisomerase II for eukaryotic cells for UNTANGLING DNA MOLECULES dna gyrase in bacteria and topoisomerase II in eukaryotic cells have the ability to untangle DNA molecules an example of how DNA gyrase in bacteria and topoisomerase II in eukaryotes accomplish the untangling of DNA CIRCULAR DNA MOLECULES ARE SOMETIMES INTERTWINED FOLLOWING THE PROCESS OF DNA REPLICATION circular dna molecules are sometimes intertwined following the process of DNA replication occurring these interlocked molecules of DNA, these intertwined molecules of DNA a situation that occurs to circular DNA molecules sometimes after DNA replication, can be sorted out and untangled by DNA gyrase/topoisomerase II there is a SECOND TYPE OF ENZYME TOPOISOMERASE I topoisomerase I is responsible for relaxing negative supercoils

Griffith experimentation critical and unexpected result

the critical and unexpected result of the experiments implemented by Griffith was found in one particular experiment that he conducted in a particular set of experiments, in particular experimentation that Griffith implemented, he had a critical and unexpected result within specific experimentation that Griffith implemented on the mice utilizing strains of streptococcus pneumoniae, particularly the S and R strains, within specific experimentation he implemented, he observed an unexpected and critical result what was this unexpected and critical result that Griffith observed through his experimentation in this particular experimentation that he implemented, the type R bacteria were mixed with heat-killed type S bacteria in the particular experimentation that Griffith implemented that resulted in the critical and unexpected result, the type R bacteria were mixed with the heat killed type S bacteria the type R bacteria (non-propagating bacteria due to the inability to secrete the polysaccharide capsule that allows a strain of streptococcus pneumoniae to escape attack from the immune system of the organism that it is trying to infect) were mixed with heat killed S bacteria (therefore nonfunctional, nonviable, and non-propagating bacteria that would not be able to infect an organism, though alive type S bacteria would indeed be functional, viable, and propagating due to its secretion of the polysaccharide capsule that allows it to escape attack from the immune system of the organism that it is attempting to infect and therefore allows the strain to propane and proliferate within the bloodstream of the organism and ultimately kill the organism) when live type R bacteria was mixed with heat-killed type S bacteria, the expected result is that the mouse would live however the mouse did not live, the mouse injected with this mixture of live type R bacteria and heat killed type S bacteria died why did this mouse die? what can accounts for these results of the mouse dying when by all expectations the mouse should indeed not have died? because living type R bacteria could not proliferate due to its inability to secrete the polysaccharide capsule that allows particular strains of streptococcus pneumoniae to escape attack from the immune system of the organism that they are trying to infect, because the live strain of type R bacteria could not propagate and proliferate within the bloodstream of the mouse and kill the mouse, the interpretation of the data collected from this experimentation is that something from the heat-killed, dead type S bacteria was transforming the live type R bacteria in the mixture into live type S bacteria that was able to propagate and proliferate within the blood stream of the mouse and killl it Griffith designated this process of something from the heat killed and dead S bacteria transforming the live type R bacteria into viable live type S bacteria as transformation Griffith designated this process of something from the heat killed and dead type S bacteria transforming the live type R bacteria into viable live type S bacteria as transformation Griffith designated this process of something from the heat killed and therefore dead type S bacteria transforming the live type R bacteria into viable live type S bacteria as transformation Griffith designated the unidentified substance from the heat killed and dead type S bacteria that caused the transformation of the live type R bacteria into viable type S bacteria, designated this entity deemed responsible fro this transformation as the transformation principle WHAT do griffin's observations mean in genetic terms? what do griffin's observations mean in genetic terms? what do griffin's observations mean in genetic terms? what do griffin's observations mean in genetic terms? what in the world do griffin's observations mean in genetic terms? the transformer bacteria acquired the information in order to make a capsule the transformer bacteria acquired the information in order to make a capsule, the transformer bacteria acquired the information in order to make a capsule the transformer bacteria acquired the information in order to make a capsule the transformer bacteria acquired the information in order to make a capsule among different strains of streptococcus pneumoniae, variation exists in the ability to make, construct and secrete a capsule and to cause mortality/death in mice the genetic material that is necessary in order to make and construct a capsule must be replicated so that this genetic material encoding the construction of the polysaccharide capsule responsible for the propagation of a strain and mortality in mice can be transmitted from mother to daughter cells during cellular division taken together, these observations are consistent with the idea that the formation of a capsule, the formation fo the polysaccharide capsule that allows the strain of streptococcus pneumoniae secreting this capsule to escape attack from the immune system of the organism it is trying to infect, allowing the strain of bacteria that secretes this capsule to propagate and proliferate within the blood stream of an organism and ultimately kill that organism, the formation the construction of this polysaccharide capsule is governed by the bacteria's genetic material the formation, the construction of this polysaccharide capsule is governed by the bacteria' genetic material, due to the genetic material and the capsule aligning with the aforementioned four principles of information, variation, transmission, and replication the experiments that Griffith conducted showcased that some genetic material from the dead, heat killed type S bacteria had been transferred to the living type R bacteria and provided the living type R bacteria with the newfound ability to proliferate and propagate (by being able to secrete the polysaccharide capsule that allows a strain of streptococcus pneumoniae to escape the actions of the immune system of the organism it is trying to infect), and ultimately kill the organism it infects however, Griffith did not know what exactly the transforming substance was, what exactly was responsible for the specific transformation of living type R bacteria into viable type S bacteria, what exactly was responsible for shifting that advantageous trait of living type S bacteria into living type R bacteria from heat killed and therefore dead type S bacteria there were important scientific discoveries that took place when researchers recognized that someone else's experimental observations can be utilized in order to address a particular scientific question Griffith through his experiments had established the phenomenon the process of transformation, understanding that there was something being transferred from heat killed and therefore dead type S bacteria (a bacteria that produces and secretes a polysaccharide capsule that assists this particular strain in escaping attack from the immune system of the organism it is trying to infect, and also causes this particular strain to exhibit a smooth colony morphology when this strain is plated and spread on a solid growth medium) to live type R bacteria, live type R streptococcus pneumoniae (which does not secrete the polysaccharide capsule secreted by type S streptococcus pneumoniae, and therefore is not capable of escaping attack from the immune system of the organism it is trying to infect, therefore not being able to proliferate and propagate and spread within the bloodstream of the organism; this particular strain, type R streptococcus pneumoniae also presents with a rough colony morphology when it is spread and plated on a solid growth medium), in order to turn this type R bacteria this live type R streptococcus pneumoniae into live type S streptococcus pneumoniae, causing a transformation of type R streptococcus pneumonia, a nonviable and nonproliferating, non lethal strain of streptococcus pneumonia into live type R streptococcus pneumonia, a viable, proliferating, and lethal dna that would indeed ultimately kill the mouse however he was still not certain of the specifics of the mechanism that influenced and caused this transformation of live type R streptococcus pneumoniae to live type S streptococcus pneumoniae, he wasn't certain of the identity of the transforming substance, he was not certain of the identity of the transforming substance the identity of this transforming substance that caused the transformation of live type R bacteria into live type S bacteria when the two strains of streptococcus pneumoniae, the type R streptococcus pneumoniae and the heat killed and therefore dead type S streptococcus pneumoniae were mixed together and afterwards injected as a conglomeration, as a composed mixture into the mouse, was further investigated by scientists there were important scientific discoveries that took place after researchers recognized that someone else's experimental observations, particularly the observations made by Griffith in his implemented experimentation with the type R and type S strains of streptococcus pneumoniae, that those observations made by him in his implemented experimentation could be utilized in order to address that particular scientific question of what is responsible for the transformation of something, particularly perhaps what is responsible for the transformation of live type R bacteria to live type S bacteria when live type R streptococcus pneumoniae and heat killed and therefore dead type S streptococcus pneumoniae are mixed together with one another Oswald Avery, Colin MacLeod, and Macyln McCarty all realized that the observations made by Griffith in his implemented experimentation could be utilized as part of a new experimental strategy to identify the genetic material these scientists asked the question: WHAT SUBSTANCE IS BEING TRANSFERRED FROM THE HEAT KILLED AND THEREFORE DEAD TYPE S BACTERIA TO THE LIVE TYPE R BACTERIA? in order to answer this question, they incorporated additional biochemical techniques into their implemented experimental methods in order to properly answer this question, the aforementioned individuals incorporated additional biochemical techniques into their implemented experimental methods at the time of these implemented experiments, experiments that were being conducted by the aforementioned scientists in the 1940s, researchers already knew that: DNA, RNA, proteins, and carbohydrates are the major constituents of living cells DNA, RNA, proteins, and carbohydrates are the major components, the major constituents composing living cells; DNA, RNA, proteins and carbohydrates DNA, RNA, proteins, and carbohydrates- the major constituents and components of living cells in order to separate these components of DNA, RNA, proteins, and carbohydrates and determine which one of these components of living cells was the genetic material, the aforementioned scientists, Avery, Macleod, and McCarty utilized established BIOCHEMICAL PURIFICATION PROCEDURES the aforementioned scientists utilized established and verifiable biochemical purification procedures, and through the implementation of these established and verifiable biochemical purification procedures, prepared bacterial extracts from type S strains of streptococcus pneumoniae containing each type of these molecules they prepared bacterial extract from type S strains of streptococcus pneumoniae containing each type of molecule, dna, RNA, proteins, and carbohydrates, the main constituents of living cells after many repeated attempts with different types of bacterial extracts of type S strains of streptococcus pneumoniae containing the 4 primary constituents of cells, DNA, RNA, proteins, and carbohydrates, the aforementioned scientists discovered that only one of their bacterial extracts, only one of their bacterial extracts, in particalr the one that contained purified DNA, was able to convert the live type R bacteria into live type S bacteria, viable, proliferating, and able to ultimately kill the organism when this extract was mixed with type R, bacteria, some of the bacteria were indeed converted and transformed into type S bacteria when this particular type of bacterial extract, a bacterial extract containing purified DNA from the type S strain of streptococcus pneumoniae, when this particular type of extract specifically containing the purified DNA of the type S streptococcus pneumoniae strain was mixed with live type R streptococcus pneumoniae, some of the type R streptococcus pneumonia was observed as having transformed into live type S streptococcus pneumoniae, viable, proliferating streptococcus pneumoniae that would ultimately kill any organism that it infected however, this only occurred when this particular bacterial extract of the streptococcus pneumonia bacteria occurred, the bacterial extract of purified dna from the type S strain of streptococcus pneumonia mixed with type R streptococcus pneumoniae if there was no dna extract added, then no type S streptococcus pneumoniae bacterial colonies were observed on the petri plats if there was no DNA extract added, then no type S streptococcus pneumoniae bacterial colonies were observed on the petri plates when the extract from the type S streptococcus pneumoniae strain was mixed with the type R streptococcus pneumonia strain if the extract from the type S streptococcus pneumoniae strain did not contain the DNA extract in particular, then when this extract not containing DNA from the type S streptococcus pneumoniae was mixed with the type R streptococcus pneumoniae on the petri plate, there were no type S streptococcus pneumoniae colones observed on the petri plate a biochemist may point out that a DNA extract may not be 100% pure DNA (despite the utilization of DNA purification techniques when extracting DNA from the type S streptococcus pneumoniae) in fact, purified extract might contain small traces of other substances that may be responsible for the transformation of type R streptococcus pneumoniae to type S streptococcus pneumoniae in this particular case if the purified extract contains traces of other substances then there is no verifiable conclusion indicating that solely DNA is responsible for the transformation of substances, that DNA is the genetic material in responsible in all cases for transformation, and in this particular case responsible for the transformation of live type R streptococcus pneumoniae to live type S streptococcus pneumoniae the argument can be made that a small amount of contaminating material, a trace amount of contaminating material within the purified extract, within the purified sample, a trace amount of contaminating material within the DNA extract might actually be the genetic material the most likely contaminating substances in this particular case, where there was a DNA extract taken from the type S strain of streptococcus pneumoniae, the most likely contaminating substances in the DNA extract in this case would be RNA or protein, two substances that could be considered responsible for the transformation of type R streptococcus pneumoniae to type S streptococcus pneumoniae in order to then further verify that the DNA particular, the DNA in the extract was indeed the sole determinant completely responsible for the transformation of type R streptococcus pneumoniae to type S streptococcus pneumoniae, the aforementioned scientists, Avery, MacLeod, and McCarty treated the sampels of the DNA extract the took from the type S streptococcus pneumoniae with enzymes that digest: DNA- enzymes that digest DNA are designated as DNase RNA- an enzyme that digests DNA is designated as RNase protein- an enzyme that digests protein is designated as proteinase when the DNA extracts were treated with RNase or proteinase, the enzyme that digests RNA and the enzyme that digests proteins, therefore ridding of the two potential contaminants within the DNA extract that could be responsible for the transformation of live type R streptococcus pneumoniae into live type S streptococcus pneumoniae, the type R streptococcus pneumoniae was still converted and transformed into type S streptococcus pneumoniae, colonies of type S streptococcus pneumoniae were still observed on the petri plate when the DNA extract was treated with RNAse and proteinase, digesting and destroying the RNA and proteins within the sample, and then mixed with type R streptococcus pneumoniae this indicated that the RNA and the proteins were not responsible fro the transformation of type R streptococcus pneumoniae to type S streptococcus pneumoniae, as the DNA extract from the type S streptococcus pneumoniae was still able to transform type R streptococcus pneumonia to type S streptococcus pneumoniae, even when the RNA and the proteins within this extract were digested these results indicated that any remaining RNA or protein within the DNA extract taken from the type S strain of streptococcus pneumoniae was not acting as the genetic material that transformed the type R streptococcus pneumoniae into type S streptococcus pneumoniae however, when the DNA extract taken from the type S strain of streptococcus pneumoniae was treated with DNase, the enzyme that digests DNA, when this DNA extract missing the DNA was mixed with type R streptococcus pneumoniae, the type R streptococcus pneumoniae was no longer converted to type S streptococcus pneumoniae, there were no colonies of type S streptococcus pneumoniae found on the petri plate where the DNA extract from type S streptococcus pneumoniae and type R streptococcus pneumoniae were mixed these results indicated that the degradation, the destruction, the digestion of the DNA in the extract by the DNAase prevented the conversion of type R to type S this interpretation is consistent with the original yet previously unverifiable hypothesis that the DNA is the genetic material the transforming principle responsible for transforming type R streptococcus pneumoniae into type S streptococcus pneumonia is DNA

blood transfusions and the importance of blood typing

the donor's blood has to be an appropriate match with the recipient's blood in order for the blood transfusion to be successful a person with type O blood has the potential to produce antibodies against both A and B antigens if they are the recipient of A, B, or AB blood they can only accept O blood bc they produce antibodies against the antigens located on blood cells from A, B, or AB after these antibodies against these A and B antigens are produced by the O receipt, they will react with the donated red blood cells and cause them to conglomerate and agglutinate this is a life threatening condition that causes the blood vessels to clog up, therefore they don't function A blood type- can only receive A and O blood cannot receive B and AB blood B blood type- can only receive B and O blood cannot receive A and AB blood AB blood type- can only receive AB blood, A blood, B blood, and O blood O blood type- can only receive O blood cannot receive A, B, or AB blood

a cross involving a two-gene interaction

the first case of two different genes interacting with one another in order to affect a single trait (so a single trait and phenotypic expression of this trait was impacted by multiple genes and their respective alleles) was discovered in 1906 by William Bateson and Reginald Punnet this case was in regards to comb morphology in chickens a Wyandotte chicken breed with a rose comb was crossed with a Brahma with a pea comb all of the offspring of the first filial generation had a walnut comb when the first filial generation offspring were bred, the second filial generation consisted of offspring with the following genotypic in these ratios: 9 walnut : 3 rose : 3 pea : 1 single look at notes

the formation of chromosomal loops

the formation of chromosomal loops helps to make the bacterial chromosome more compact the formation of chromosomal loops helps to make the bacterial chromosome within the bacterial cell a bit more compact in order for the bacterial chromosome, with millions of nucleotides and thousands of genes (a very long DNA sequence and thus a v large bacterial chromosome) to fit into the bacterial cell, to fit into both the bacterial cell and a particular nucleoid region of this bacterial cell, the chromosomal DNA of a bacterial chromosome needs to be compacted a 1000-fold THE CHROMOSOMAL DNA OF A BACTERIAL CHROMOSOME IN ORDER FOR IT TO FIT WITHIN A BACTERIAL CELL NEEDS TO BE COMPACTED A 1000 FOLD part of this compaction process of the chromosomal dna within the bacterial chromosome of a bacterial cell involves the implementation of the following process: the formation of loop domains ultimately, the compaction process of chromosomal DNA of a bacterial chromosome so the DNA and the chromosome constituting and containing it can fit into the bacterial cell involves the formation of LOOP DOMAINS a loop domain is a SEGMENT OF CHROMOSOMAL DNA this segment of chromosomal DNA is folded into a structure that resembles a loop a loop domain is a segment of chromosomal dna that is folded into a particular structure that resembles and looks like a loop there are DNA BINDING PROTEINS THAT ANCHOR THIS LOOP STRUCTURE IN PLACE there are loop domains, these loop domains are segments of chromosomal dna that are folded into loop like structures and there are DNA BINDING PROTEINS that anchor these loop structures, these loop domains in place the number of loops within a bacterial chromosome of a bacterial cell of a particular bacterial species varies according to the particular size of the bacterial chromosome, and the bacterial species whose DNA it comprises within E coli Escherechia coli for example, a bacterial chromosome within a bacterial e coli cell contains about 50 to 100 loop domains THERE ARE 40000 to 800000 BASE PAIRS OF DNA IN EACH LOOP within e coli, a bacterial e coli cell, there are about 50-100 loop domains, and within each individual loop domain, there are 40,000 to 80,000 base pairs per loops domain this looped structure within the bacterial e coli cell compacts the circular bacterial chromosome about 10-fold the above aforementioned conformation of the chromosome compacts the circular bacterial chromosome about 10-fold, the 50 to 100 loop domains with 40,000 to 80,000 base pairs within a single loop domain

particulate theory of inheritance

the genes governing traits (determining what the traits of the offspring will be) are inherited as discrete units that do not change when they are passed from parent to offspring, but merely interact with one another

genotype

the genetic composition of an individual

X-inactivation center (Xic)

the genetic control of inactivation is not completely understood and clarified at the molecular level it is not understood how the molecular processes influence and/or possibly control the inactivation of X chromosomes, and how they do so there is a short region on the X chromosome known and designated as the X-inactivation center (Xic) and this short region located on the X chromosome is integral in regards to control and influence of X inactivation X chromosomes are counted by researchers finding and identifying them to the Xic regions (Xic regions are the markers searched for in order to identify X chromosomes, so if for example you find two Xic regions within a karyotype of an individual, that means that that individual has two X chromosomes and is a female) the two individuals that identified the Xic region were Eeva Therman Klaus Palau the identified the Xic due to its integral and important role in influencing and controlling the process of X inactivation the presence of the Xic region on an X chromosome is integral to the occurrence of X inactivation the Xic region needs to be present on an X chromosome in order for the process of X inactivation to occur the two researchers mentioned above Eeva Therman and Klaus Palau discovered that if you are looking at the karyotype of a female and find that there is only one Xic region in the entire chromosomal set, that indicates that the female only has one X chromosome and the other one is not counted the Xic region on one of the X chromosomes is not present due to a chromosomal mutation, and even thought this X chromosome with the mutation exists within the female and is technically within the karyotype, it is not identified as such due to its lack of the Xic region, and therefore X inactivation of one of the X chromosomes does not occur, due to the fact that only one X chromosome in this individual has been identified therefore there are two active X chromosomes within this individual, as no X inactivation has occurred this condition of two active X chromosomes is a lethal condition, that will result in the death of the developing female embryo in humans

chloroplast genomes

the genomes of chloroplasts tend to be substantially larger than mitochondrial genomes they therefore (due to the size of their genomes being substantially larger than those of mitochondria) have a larger number of genes than mitochondrial genomes a typical chloroplast genome- is approximately 100,000 to 200,000 base pairs in length this length is 10 times larger than the length of typical mitochondrial genomes, which are around 17,000 base pairs in length the DNA within chloroplasts is known as chloroplast DNA (cpDNA) looking at the chloroplast DNA of the tobacco plant the chloroplast DNA of the tobacco plant is in its totality, a circular DNA molecule this circular DNA molecule/chromosome within the chloroplast of a tobacco plant cell contains 156,000 base pairs of DNA this circular DNA molecule/chromosome within the chloroplast of a tobacco plant cell contains bw 110 and 120 different distinct genes the genes of this circular DNA molecule found within the chloroplasts of tobacco plant cells code for: - ribosomal RNAs - transfer RNAs - a multitude of proteins integral to the process of photosynthesis many of the proteins that function within the chloroplast are coded for by genes within the plant cell's nucleus, rather than the genes within the chloroplast the proteins that are to function within the chloroplast that are coded for by DNA within the plant cell's nucleus contain chloroplast targeting signals, that will eventually lead them to chloroplasts where they will carry out and implement their function (similar to mitochondria, where mitochondrial proteins are transferred from the cytosol to within the mitochondrion in order to function there, despite being coded for by DNA within the nucleus)

hypothesis testing

the goal of hypothesis testing is to determine if the data from the genetic crosses that we conduct is consistent with a particular pattern of inheritance/governing laws of inheritance for particular traits an example of this is a geneticist studying the inheritance of body color and wing shape in fruit flies, how fruit flies inherit their body color and wing shape, how this inheritance is governed by certain principles, what those principles are there would most likely be a question about the F2 generation: Do the observed numbers of offspring agree with the predicted/expected numbers based on Mendel's laws of segregation and independent assortment? recall that not all traits follow Mendel's laws of segregation and independent assortment, a Mendelian pattern of inheritance to discover whether or not traits follow a Mendelian pattern of inheritance, you need to look at crosses and conduct a quantitative analysis of the offspring looking at the observed outcome, the experimenter can possibly make a proposed tentative hypothesis hypothesis testing provides an objective, statistical method to evaluate if the observed data agree with a particular hypothesis or not

molecular genetics

the goal of this field of study is to understand how genetics works at the molecular level the scientists within this field want to understand the molecular features of DNA, how these features (the molecular features) influence the establishment and expression of genes most experiments of molecular genetics occur within a laboratory the focus of these experiments often becomes DNA, RNA, and proteins

maternal effect at the molecular and cellular level

the inheritance pattern of maternal effect genes can be explained by a biological process that only occurs in females: oogenesis (the production of eggs in females) when an animal oocyte (oocyte is another word for egg) matures, many surrounding maternal cells (these surrounding maternal cells are called nurse cells) there are nurse cells surrounding this animal oocyte (egg) that is maturing these nurse cells provide the animal oocyte with nutrients and other materials an example of how the process of oogenesis and the concept of nurse cells providing the maturing animal oocyte with nutrients and other things relates to the maternal effect in water snails (where the mother's genotype is the sole determinant of the offspring's phenotype, regardless of the genotype/allelic combination and phenotype of the male, and regardless of the genotype/allelic combination of the offspring) there's a female that is heterozygous for the snail-coiling maternal effect gene depending on the outcome of meiosis in this heterozygous dextral female, the haploid egg/gamete involved in reproduction will end up with one of the two alleles (either the D or d allele, but not both, as gametes can only have one allele that matches up with the allele of the other reproductive organism's gamete, to create an allelic combination that determines the offspring's phenotypic expression) the surrounding nurse cells around this maturing oocyte (maturing egg) provide both D and d gene products (mRNA and proteins are the products of these alleles that the nurse cells provide to the maturing oocyte) these gene products of mRNA and proteins produced by the D and d alleles are incorporated into the maturing oocyte (they are transported into this maturing oocyte/egg) therefore the maturing oocyte/egg has received both the D and d allele gene products of mRNA and proteins coded for by these alleles these gene products of mRNA and proteins that have been transported from the nurse cells to the maturing oocyte persist a long time after the egg has been fertilized and the zygote has begun to develop the gene products of mRNA and proteins provided by the nurse cells to the maturing oocyte (egg) remain in the maturing oocyte through fertilization and and the gene products of the nurse cells (that are reflective of the allelic combination/genotype of the mother) influence the early developmental stages of the embryo (the genotype of the embryo is determined by these gene products mRNA and proteins that stay with the maturing oocyte how does the relationship bw oogenesis (the formation of oocytes/eggs) and maternal effect genes connect to the topic of snail coiling? a homozygous dominant dextral female with the allelic combination DD will pass on the products of the D allele to the maturing oocyte (the nurse cells surrounding the maturing oocyte will produce the products of the D allele, mRNA and proteins, that will be transported into the maturing oocyte) during the early stages of embryonic development (when fertilization has occurred and the zygote -the combination of the two haploid gametes- egg and sperm- is maturing), these gene products cause the egg cleavage to occur in a particular manner the manner in which the egg cleavage occurs (which is due to the gene products within it transported from the nursing cells that produced those products) is a cleavage that promotes a right handed body plan, promotes a dextral/right orientation of the shell and internal organs a heterzygous dominant female with the allelic combination Dd has eggs with the gene products coded for by both the D and d alleles, and the egg will still cleave in a way that promotes a dextral/right conformation of the shell/internal organs a homozygous recessive female with the allelic combination dd contributes only the gene products of the d allele to the maturing oocyte (the nurse cells that surround this maturing oocyte produce the products mRNA and/or proteins coded for by the d allele, and these products of the d allele are transported into the maturing oocyte), and due to these gene products being in this mature oocyte, and remaining there through fertilization and zygote maturation, the egg cleavage occurs in a way that promotes a sinistral/left conformation of the shell/internal organs the genotype of the sperm is completely irreverent and has no influence on the phenotypic way that the offspring present, bc the expression of the sperm's allele will occur too late to have a substantial or rather any impact on the offspring and their morphological characteristic in regard to cell and internal organ orientation (that is determined early by the egg, it's gene products, and the egg cleavage) how does dextral and sinistral coiling occur in cells, what cause of dextral and sinistral coiling can these two conformations be traced to? the orientation of the mitotic spindle at the two to four cell stage of embryonic development, where there are two cells that are combined into a zygote that split into two cells and from there, four dextral and sinistral shells are mirror images of one another

the inheritance pattern of suppressive petites

the inheritance pattern of suppressive petites is a tad complicated this is due to the fact that the suppressive petite strain has the majority of its mitochondrial DNA intact that it can pass on to its offspring/daughter cells, as does the wild type strain with a full mitochondrial genome that it also passes on to its offspring/daughter cells therefore in a cross bw a wild type strain and a suppressive petite strain, the daughter cells inherited both the wild type mitochondria and suppressive petite mitochondria, so it is a bit harder to understand how we get an all petite ratio one hypothesis is that the suppressive petite mitochondria inherited by the daughter cells replicate and proliferate faster than the wild type mitochondria, and therefore wild type mitochondria are not maintained through proliferation in the cytoplasm another hypothesis is that there are genetic exchanges bw the two mitochondrial genomes (the wild type and suppressive petite mitochondria exchange genetic information) and this exchange of mitochondrial genetic information produce a defective population of mitochondria, and therefore all of the daughter cells showcase as petite due to this defective population of mitochondria

inheritance pattern of x-linked genes

the inheritance pattern of x-linked genes can be revealed by reciprocal crosses in Ch.3- a lot of species have organisms that differ in their sex chromosome composition, males and females determined by varying factors depending on the species within human the variants are XX-female and XY-male in particular species, where there are variations in sex determined by particular factors (and organisms can be designated as male or female based on these particular factors), there are particular traits that are governed by genes found on these sex-determining factors (in this case, chromosomes) genes are found on the sex chromosomes in humans for these traits that are found on sex chromosomes, the outcomes of crosses between individuals and the phenotypic expression of these sex-linked traits is dependent upon both the genotypes being crossed as well as the sexes of both the parents and offspring (as traits can be X-linked or Y-linked)

peas

the inheritance patterns of peas mimic those of -humans -mice -fruit flies -corn

applications of Mendel's work

the laws of inheritance he established can be used in order to predict the results and outcomes of genetic crosses his laws of inheritance can be applied in agriculture- plant and animal breeders are concerned w the types of offspring their crosses will produce they utilize the laws of inheritance in order to produce the organisms they desire with the most optimal traits these farmers, plant and animal breeders can successfully commercially produce crops and livestock the applications of Mendel's work also apply to people wanting to successfully predict the characteristics their child will have for the health of their own child they want to know if their child is susceptible to particular genetically caused conditions, and Mendel's work assists in the understanding of the probability, the likelihood that an offspring will have a certain condition there are different ways of going about probability calculations, the one you select is based on the circumstances the three main mathematical operations are: -sum rule -product rule -binomial expansion equation the above methods help us in determining the probability of particular outcomes when crossing two individuals in order to utilize the above we need the following information: -genotypes of the parents -pattern of inheritance of a given trait the above calculations can also be utilized in hypothesis testing if there is a researcher that wants to determine the genotypes and patterns of inheritance for traits that have not yet been established, they would utilize the above mathematical operations conducting crosses and analyzing their outcomes would be one approach to the above scenario the resulting proportions of traits amongst offspring can help the researcher propose a hypothesis about the possible laws governing this trait

somatic cells

the majority of cells of the human body that are not directly involved in sexual reproduction

pleiotrophy

the majority of genes don't simply have one effect, but rather multiple effects through a cell or organism genes usually have multiple impacts on an organism rather than simply influencing the phenotypic expression of one trait pleiotrophy is designated as the multiple effects of a single gene on the phenotype of an organism (so a single gene can effect the phenotypic expression of multiple traits, and that phenomenon is designated as pleiotrophy) why does pleitrophy occur, why does this phenomenon occur where a single gene affects the phenotypic expression of multiple traits 1) the expression of a single gene can affect the function of a cell in multiple ways an example of these is that if there is a defect in a single gene coding for a microtubule protein, and therefore a defect in the microtubule protein, cell division and cell movement as a whole may be affected by this small defect 2) a gene can be expressed different cell types in a multicellular organism, and therefore serve different functions and have different effects (variants of a character) in these differing cells, depending on what an individual cell is 3) a gene can be expressed at different stages of development, which may change the degree of phenotypic expression of whatever this gene is coding for, due to the gene being at a particular stage of development in the majority of cases, the expression of a gene is pleiotrophic in regards to the characteristics of an organism, so the expression of one gene can affect and will affect a multitude of characteristics in an organism (more than one characteristic) the expression of one gene in an organism can indirectly or directly influence the expression of another gene and that gene's function, as well as the function of whatever that gene is coding for (and those genes that it affects will in turn affect the original gene itself) researchers are able to discover pleiotrophy and understand these relationships bw a multitude of genes and the phenotypic traits they code for through research an example of a pleiotrophic mutation is cystic fibrosis cystic fibrosis is inherited recessively the gene that codes for cystic fibrosis was identified in the late 1980s the gene for cystic fibrosis encodes a protein known as the cystic fibrosis transmembrane conductance regulator (CFTR) the cystic fibrosis transmembrane conductance regular regulates ion balance by allowing the transport of chloride ions (chloride anions) across epithelial cell membranes it controls the ion balance on both sides of epithelial cell membranes by regulating the transport of chloride ions across these very membranes the mutation that causes cystic fibrosis make the Cl- transporter protein cystic fibrosis transmembrane conductor protein nonfunctional the effects of this are for starters, that the ion balance on either side of epithelial cell membranes is no longer regulated the other effects of this include: the movement of Cl-, chloride anions across the epithelial cell membranes impacts water transport across membranes therefore, if the movement of Cl- chloride anions is no longer occurring across the epithelial cell membranes, then the most severe symptom of cystic fibrosis, thick mucus in the lungs, occurs due to the water imbalance, (which is due to water transport being impacted by the movement of chloride anions across epithelial cell membranes, and becoming imbalanced due to imbalance of ions on either side of these epithelial cell membranes, which is due to the non functionality of the CFTR protein and the non regulation of ion movement that this non functionality causes) another effect is that in sweat glands, the normal chloride anion transporter functions by recycling salt out of the sweat glands, and back into the skin before the salt can be lost to the outside world/atmosphere people afflicted with cystic fibrosis have very salty sweat, due to the inability of the normal chloride anion transporter to recycle the salt out of the sweat glands and back into the cells because the Cl- transporter is not functioning properly and recycling the salt from the sweat glands back into the epithelial cells, the salt is lost to the outside world/atmosphere, and the individual's sweat is excessively salty a test for cystic fibrosis is a measurement of the amount of salt in an individual's sweat/on their skin another effect of cystic fibrosis occurs in the reproductive system of males with cystic fibrosis it occurs in males who have a homozygous recessive allelic combination for cystic fibrosis (they will therefore be affected as cystic fibrosis is inherited recessively and therefore you need two recessive alleles in order to phenotypically express this condition these homozygous recessive males may be infertile the infertility may be due to the vas deferent being absent/underdeveloped and therefore unable to do its function (which is transporting sperm from the testes) due to this being a symptom/effect of cystic fibrosis, it is presumed that a normally functioning CFTR protein/Cl-transporter is necessary for the proper development and functionality of the vas deferens when the embryo is forming

phenotype

the observable characteristics (morphological, physical, and behavioral)

blending inheritance

the observations of Joseph Kölreuter aligned with blending inheritance this viewpoint suggests that the factors dictating and determining hereditary traits can blend together as you progress from generation to generation not true however, and Mendel disproved this theory as well as pangenesis

genetic polymorphism

the occurrence of more than one wild type allele within a large population there are multiple wild-type alleles an example of polymorphism- the elderflower orchid, Dactylorhiza sambucina this species ranges throughout Europe, and both yellow and red-flowered individuals are prevalent therefore both yellow and red are considered wild type, and the alleles coding for yellow and red flowers are considered wild type allele wild type allele at the molecular level: the wild type allele typically encodes a protein that is made in the proper amount and functions normally (probably within a heterozygote, where this dominant wild-type allele is present alongside a recessive allele, this wild-type allele producing 50 percent of the protein is enough for the variant its coding for to be expressed wild type alleles, and having them promotes the reproductive success and continuation of organism in their native environments (due to natural selection and the advantageousness of a wild type allele coding for a wild-type trait)

discovery-based science

the other general type of scientific approaches somewhat of a backwards analysis, working backwards in order to reach conclusions an example of this is scientists analyzing the genes found in cancer cells in order to see which genes are mutated, the genes that are usually normal within normal cells, but have become mutated and present as such in cancer cells the scientist does not go in with a hypothesis as to which genes are mutated, but discovers it as they go through the process it is the collection and analysis of data without the need for a preconceived established hypothesis

the influences on traits

the outcome of a trait/the way that a trait is represented can be influenced by the following: - level of protein expression - the sex of the individual (sex-linked traits where the traits are linked to the X or Y chromosome) - the presence of multiple alleles of a given gene (more than two, defying the classic example of 2 alleles and one being dominant over the other) - environmental affects - also there are situations where two different genes can both influence and contribute to the way a particular trait is expressed

dosage compensation studies

the phenomenon of dosage compensation has been studied extensively within particular species including: - Drosophila - Caenorhabditis elegans (a nemotode) dosage compensation occurs along different mechanisms (different methods that result in different allelic combinations expressing the same phenotypic trait despite the expectation of them not to result in the same phenotype being expressed due to a difference in gene dosage) within female mammals, there is an equalization that occurs to the expression of X-linked genes, where one of the two X chromosomes is turned off and becomes a Barr body, therefore all the genes on one of the X chromosomes is inactivated dosage compensation in Drosophila melanogaster in Drosophila melanogaster, dosage compensation is accomplished by the male flies of Drosophila melanogaster with the process of doubling the expression of the majority of X-linked genes (they only have one X chromosome, and therefore only one set of alleles (1/2 of all the allelic combinations of X-linked genes) are expressed therefore in Drosophila melanogaster males, the expression of these alleles that serve as 1/2 of all allelic combinations of X-linked genes is doubled, so there technically is the appropriate number of alleles expressed, and complete allelic combinations of X-linked genes being expressed in the male (despite the male having only one X chromosome) dosage compensation in Caenorhabditis elegans (a nematode) the XX animal (the animal with two X chromosomes) is a hemaphrodite this XX Caenorhabditis elegans organism produces both sperm and egg cells/oocyte the animal carrying a single X chromosome- this is a male that produces only sperm the difference bw these two, and why one produces both sperm and eggs while the other only produces sperm:the XX caenorhabditis elegans organism that is also a hermaphrodite (and is able to produce both eggs and sperm) diminishes the expression of X-linked genes (these X-linked genes are diminished in regards to how much they are expressed) and the expression of these genes is limited to approximately 50 percent of that in the male dosage compensation In birds the Z chromosome- in birds is a very large chromosome the Z chromosome in birds is usually the fourth or fifth largest chromosome the Z chromosome also contains the majority of known and designated sex-linked genes the W chromosome is generally a much smaller chromosome, designated as a micro chromosome this microchromosome contains a high proportion of repeat sequence dna this high amount of repeat sequence dna does not encode many genes, so there are very few genes found on chromosome W, the micro chromosome in birds male birds have the allelic combination ZZ female birds have the allelic combination ZW there was research done on the level of expression of a Z-linked gene this researched Z-linked gene encodes an enzyme known as aconite male birds express twice as much of the enzyme aconitase than female birds do so in males birds, the amount of aconitase is twice that of the amount usually in female birds therefore researchers concluded that dosage compensation does not occur within birds, due to this consistent difference in phenotypic expression in organisms with different levels of expression of the same gene within allelic combinations more recently, there has been research of hundreds of Z-linked genes within chickens the new research that has been done on Z-linked genes in chickens (genes linked to the Z chromosome in chickens) indicates a trait of dosage compensation within birds the research on the Z chromosome and Z-linked genes concluded that the birds lack a general mechanism for dosage compensation dosage compensation that would impact and influence the expression of Z-linked genes (ensuring that even if an organism didn't have a particular amount of Z-linked genes, and two organisms had different levels of gene expression of Z-linked genes, the phenotypic expression of these organisms for the traits coded for by these Z-linked genes would be the same) the patterns of gene expression of Z-linked genes bw males and females are found in many variations amongst birds, so dosage compensation is not found amongst bird populations apparently, some Z-linked genes may be dosage compensated within birds, but the majority of Z-linked genes are not dosage compensated

phenotypes of leaves

the phenotypes of leaves (how the leaves can present as green, white, or variegated patches of green and white) is due to the type of chloroplasts found within leaf cells the kinds of chloroplasts found within leaf cells influences the kind of phenotypic trait the leaf containing those leaf cells with those particular chloroplasts present the wild-type condition for the color of leaves is green, and this phenotypic expression and presentation of green leaf color is due to the presence of normal chloroplast within leaf cells that produce green pigment the recessive condition for the color of leaves is white, and it is attributed to a mutation in a gene within the inherited chloroplast DNA this mutation in a gene within the inherited chloroplast DNA diminishes the synthesis of a green pigment the green pigment is no longer produced when there is the presence of a mutation within this particular gene within the inherited chloroplast DNA heteroplasmy- this is a condition where a cell contains both kinds of chloroplasts, the normal chloroplasts that functionally produce green pigment, as well as the chloroplasts with a mutation in a particular gene that reduces and diminishes the synthesis of green pigment, this condition is known as heteroplasty a leaf cell that contains both types of chloroplasts (both the normal one that functionally produces green pigment and the abnormal ones with mutations in genes that diminish the production of green pigment) will still present as green, due to the presence of chloroplasts that are producing green pigment which will overwhelm and present over the absence of green pigment coded for by the mutated chloroplasts therefore, how does a variegated phenotype occur? let's take a look at the leaf of plant that proliferated and was developed from a fertilized egg that contained both types of chloroplasts (so a heteroplastic egg, containing the normal chloroplasts that code for the synthesis of green pigment, as well as the mutated chloroplasts that diminish the production of green pigment) as the plant grows and develops from this fertilized heteroplasmic egg, within each plant cell to each plant, the two types of chloroplast (the normal and mutated ones) are distributed unevenly to the daughter cells thus during proliferation, many daughter cells end up with one type of chloroplast, and many with the other, and therefore present differently phenotypically on occasion, a daughter cell may only inherit the mutated chloroplasts that diminish the synthesis of green pigment, and therefore, these leaf cells with solely the abnormal chloroplasts will present as white this leaf cell that presents as white and carries only mutated chloroplasts that diminish the production of green pigment will pass these chloroplasts on to daughter cells during proliferation, and this will result in a collection of cells/a section of the plant that presents as white on occasion, a daughter may inherit the normal chloroplasts that produce green pigment in addition to the mutated chloroplasts the diminish the production of green pigment, and (due to our knowledge that the normal chloroplasts will overwhelm the mutated chloroplasts) will present as green then as this leaf cell presenting as green proliferates, it will create daughter cells with the same genotype that also present as green due to the presence of normal chloroplasts coding for green pigment, and therefore there will be a collection of cells/a sector of the plant that presents as green looking at a female parent that is variegated (has white and green proteins), the female parent is able to transmit green, white, or a mixture of these kinds of chloroplasts to the egg cell that will contribute to the formation of these offspring, which will then determine the offspring's phenotypic presentation

wild-type alleles

the prevalent alleles coding for prevalent traits found within a natural population

the primary function of genetic material

the primary function of genetic material, the primary function of DNA and chromosomes (a structure composed of DNA and chromatin) is to STORE THE INFORMATION NEEDED TO PRODUCE THE CHARACTERISTICS OF AN ORGANISM the dna is responsible for storing the necessary information required to code for and produce the phenotypic characteristics of an organism WHAT DO CHROMOSOMAL SEQUENCES DO?: THE SYNTHESIS OF RNA AND CELLULAR PROTEINS THE REPLICATION OF CHROMOSOMES THE PROPER SEGREGATION OF CHROMOSOMES THE COMPACTION OF CHROMOSOMES these four above activities are what the chromosomal sequences are responsible for they are responsible for the synthesis of rna and cellular proteins they are also responsible for the replication of chromosomes, the replication of genetic material that occurs when the process of mitosis or meiosis is implemented the proper segregation of the chromosomes during these above processes, they need to be sorted and organized properly in order to ensure that each daughter cell in mitosis receives the exact same, identical amount of genetic material the proper segregation of the chromosomes is also important during anaphase 1 of meiosis 1 (which leads to meiosis II and the proper segregation of genetic material there) as well as anaphase 2 of meiosis II, which will result in the formation of haploid gametes the compaction of chromosomes as well, in order for these chromosomes to fit within living cells chromosomes, the genetic material that they contain is far too large to fit within the diameter of the nucleus that is about 2 to 4 micrometers, and therefore the DNA becomes extremely compacted into chromosomes so that all of the genetic material can fit into the nucleus the DNA also undergoes further compaction during the prophase stage of mitosis, meiosis 1, and meiosis 2

generation to generation imprinting

the process of genomic imprinting from generation to generation of organisms involves a multitude of things: - maintenance - erasure - de novo methylation steps looking at the given example 5.12: - the paternally inherited allele- methylated and therefore not transcriptionally active - the maternally inherited allele- not methylated, unmethylated and therefore transcriptionally active the above is true for the somatic cells of all organisms, the paternally inherited chromosome is transcriptionally inactive, and the maternally inherited chromosome is transcriptionally active we are looking at a comparison bw male and female organisms within this species both the male and the female have inherited a maternally inherited transcriptionally active chromosome, and a paternally inherited methylated and therefore transcriptionally inactive chromosome so their somatic cells are the same, in all of their somatic cells, the maternally inherited chromosome is transcriptionally active, and the paternally inherited chromosome is transcriptionally inactive the difference arises when we look at the gametes formed by these two organisms (eggs by the female and sperm by the male) when the female makes gametes (due to the fact that maternally inherited chromosomes are always marked to be transcriptionally active, and the chromosomes she will give to her offspring will definitively be maternally inherited, as she is the mother, and the offspring will be inserting that particular chromosome from her), the imprinting making her paternally inherited chromosome is erased (bc when it is passed on to the offspring, it will be considered maternally inherited as it comes from her, the female) the female will therefore, in all of her gametes, regardless of whether they hold her maternally inherited or paternally inherited chromosome (bc to her offspring they will all be considered maternally inherited), will have an unmethylated ICR region on the given chromosome they contain, and whatever gamete they pass on to the offspring, the genetic material within will be transcriptionally active, and the mother's gamete will be the sole genetic determinant for the offspring's phenotypic expression however, within the male, there is a different story in all of the males somatic cells, the maternally inherited chromosome is transcriptionally active, while the paternally inherited chromosome is transcriptionally inactive however, when it comes to the formation of the male's gametes, all of the genetic information it passes onto the offspring will be considered paternally inherited, as the offspring will inherit the genetic material from him the father all paternally inherited genetic material within this chromosome is not marked to be transcriptionally active, so this material will be transcriptionally inactive when it is passed on to the offspring (as only the maternally inherited chromosome is marked to be transcriptionally active, and therefore will act as the sole genetic determinant for the phenotype of the offspring) therefore, in gametic formation, the imprinting of the paternally inherited chromosome being transcriptionally inactive and the maternally inherited chromosome being transcriptionally active will be erased however, then a process known as de novo (de novo = new) methylation will occur in both of the ICR of both the chromosomes that the male can individually pass on its gametes (both are transcriptionally inactive due to the fact that when the offspring inherits them, the genetic material will be considered paternally inherited, and that material is not marked to be transcribed) the male organism will always pass a methylated chromosome and therefore methylated genetic material with methylated gene on to its offspring

genomic imprinting occurrences

the process of genomic imprinting occurs within a multitude of species: - insects - mammals - flowering plants the process of genomic imprinting within these species may involve: - a single gene - a portion of a chromosome - a chromosome in its entirety - all the chromosomes, 1 entire set from a parent the first example of genomic imprinting within a species was discovered by Helen Crouse in the housefly Sciara coprophilia this particular instance of genomic importuning involved an entire chromosome being marked in the species of the housefly Sciara coprophilia, the fly normally inherits 3 sex chromosomes (3 allosomal chromosomes) as opposed to 2 sex/allosomal chromosomes (a process that occurs within the majority of species) there is one X chromosome that is maternally inherited, and two X chromosomes that are paternally inherited during the process of embryogenesis (the creation of the zygote that will then be replicated and result in the proliferation of all the somatic cells composing the housefly): - within male offspring, both of the paternally inherited X chromosomes are lost during the formation of the zygote/embryogenesis, and that 1 expressed and present X chromosome establishes the offspring's sex as male - within female offspring,only one of the paternally inherited X chromosomes is lost during the formation of the zygote/embryogenesis, the presence of the 2 X chromosomes establishes the offspring's sex as female - in both sexes of the housefly Sciara coprophilia, the 1 maternally inherited chromosome is never lost therefore scientists and researchers have come to the conclusion that either: - genomic imprinting occurs on the maternal X chromosome, so it is genetically marked in order to be transcriptionally active and expressed in the offspring - genomic imprinting occurs on the 2 paternal X chromosomes are genetically marked in order to transcriptionally inactive and not expressed within the offspring, they are genetically imprinted and marked to for a loss of function

Phenylketonuria

the protein produced by the normal gene is phenylalanine hydroxylase in this disease, the individual has an inability to metabolize phenylalanine this disease can be prevented by the individual following a phenylalanine-free diet, where they do not have to absorb an amino acid they cannot metabolize the diet needs to be implemented early on in the life of the individual, bc otherwise this condition where there is a buildup of a compound the body cannot metabolize can lead to: -severe mental impairment -physical degeneration

Cystic fibrosis

the protein that is produced by the normal gene is a chloride transporter the description of this disease is that there is an inability to regulate ion balance across epithelial cells therefore, this irregular ion concentration across epithelial cells leads to: -production of thick lung mucus -chronic lung infections

Tay-Sachs disease

the protein that is produced by the normal gene is hexosaminidase A in this disease, there is a defect in lipid metabolism this condition leads to: -paralysis -blindness -early death

Sandhoff disease

the protein that is produced by the normal gene is hexosaminidase B the description of this disease is also a defect in lipid metabolism symptoms/conditions: -muscle weakness in infancy -early blindness -progressive mental and motor deterioration

Lesch-Nyhan syndrome

the protein that is produced by the normal gene is hypoxanthine-guanine phosphoribosyl transferase the description of this disease is that the individual has an inability to metabolize purines, the nitrogenous bases found in DNA and RNA leads to: -self-mutilation behavior -poor motor skills -mental impairment -kidney failure

albinism

the protein that is produced by the normal genen is tyrosinase in this disease, there is a lack of pigmentation in the skin, eyes, and hair

the proteins of the nuclear matrix

the proteins of the nuclear matrix, the proteins that compose the nuclear matrix (recall that the nuclear matrix is composed of two part, the nuclear lamina, and the inner nuclear matrix) reviewing the structure of the nuclear matrix, what composes the nuclear matrix THE NUCLEAR LAMINA COMPOSES THE NUCLEAR MATRIX IT IS ONE OF THE TWO COMPONENTS COMPOSING THE NUCLEAR MATRIX the nuclear lamina recall is a COLLECTION OF FIBERS the nuclear lamina is a collection of fibers that LINE THE INNER NUCLEAR MEMBRANE the nuclear lamina is a collection of fibers, a conglomeration of fibers that line the inner nuclear membrane the nuclear lamina is a conglomeration/collection of fibers that lines the inner nuclear membrane the proteins that compose the nuclear lamina are composed of INTERMEDIATE FILAMENT PROTEINS recall that the nuclear lamina is a collection and conglomeration of fibers that line the inner mitochondrial membrane these fibers are composed of INTERMEDIATE PROTEIN FILAMENTS the second component of the nuclear matrix is the INNER NUCLEAR MATRIX recall that the first component of the nuclear matrix is the nuclear lamina, a collection and conglomeration of fibers composed of INTERMEDIATE PROTEIN FILAMENTS that line the inner nuclear membrane the second component of the nuclear matrix is the inner nuclear matrix the structure and function of the inner nuclear matrix is widely debated and controversial, no one is really sure of a confirmed, verifiable structure and function of the nuclear matrix however, the theories are as follows: THE STRUCTURE OF THE INNER NUCLEAR MATRIX IS HYPOTHESIZED TO BE A FINE NETWORK OF IRREGULAR PROTEIN FIBERS the structure of the inner nuclear matrix is hypothesized to be a fine network of irregular protein fibers this is because, even when the chromatin is extracted from the nucleus, the inner nuclear matrix oftentimes stays intact however THE MATRIX SHOULD NOT BE CONSIDERED A STATIC STRUCTURE the nuclear matrix is VERY DYNAMIC previously implemented research INDICATES THAT THE PROTEIN COMPOSITION OF the nuclear matrix is VERY DYNAMIC AND COMPLEX previously implemented and verifiable research has concluded that the protein composition of the nuclear matrix is v complex and dynamic the protein composition of the nuclear matrix is hypothesized to have dozens or hundreds of different proteins THE PROTEIN COMPOSITION of the nuclear matrix varies depending on SPECIES CELL TYPE ENVIRONMENTAL CONDITIONS the complexity of the protein composition, and its dependence on species, cell type, and environmental conditions that cause it to be subject to change has made it difficult to both propose and pinpoint an accurate model detailing its structure there is further research that needs to be done in order to completely understand the structure and function of the nuclear matrix THE DYNAMIC NATURE OF THE INTERNAL NUCLEAR MATRIX the proteins of the nuclear matrix ARE INVOLVED IN COMPACTING THE DNA INTO RADIAL LOOP DOMAINS the proteins of the nuclear matrix are involved in COMPACTING THE DNA INTO RADIAL LOOP DOMAINS the proteins of the nuclear matrix are responsible for compacting the DNA into radial loop domains the radial loop domains that the proteins of the nuclear matrix are responsible for creating are similar to the ones previously discussed that occur in bacteria, within bacterial chromosomes during interphase, THE CHROMATIN IS ORGANIZED INTO LOOP during interphase the chromatin is organized into loops these loops that the chromatin is organized into are often 25,000 to 200,000 BASE PAIRS IN LENTH the loops that the chromatin is organized into during interphase are 25,000 to 200,000 base PAIRS IN LENGTH these loops are anchored to the nuclear matrix these loops that are 25,000 to 250,000 base pairs in length are anchored to the nuclear matrix THE CHROMOSOMAL DNA OF EUKARYOTIC SPECIES CONTAINS SEQUENCES the chromosomal DNA of eukaryotic species contains sequences these sequences contained within the chromosomal DNA of eukaryotic species are CALLED MATRIX ATTACHMENT REGIONS or SCAFFOLD ATTACHMENT REGIONS these sequences contained within the chromosomal DNA of eukaryotic species are MATRIX ATTACHMENT REGIONS - MARS SCAFFOLD ATTACHMENT REGIONS - SARS these are sequences found within the chromosomal DNA of eukaryotic species these matrix attachment regions and scaffold attachment regions are INTERSPERSED AT REGULAR INTERVALS THROUGHOUT THE GENOME these matrix attachment regions and scaffold attachment regions are INTERSPERSED AT REGULAR INTERVALS THROUGHOUT THE GENOME these matrix attachment regions and scaffold attachment regions are interspersed at regular intervals throughout the genome these matrix attachment regions and scaffold attachment regions are interspersed at regular, consistent intervals throughout the genome the MATRIX ATTACHMENT REGIONS the MARS bind to SPECIFIC PROTEINS IN THE NUCLEAR MATRIX AND FORM CHROMOSOMAL LOOPS the mars the matrix attachment regions bind to specific particular proteins within the nuclear matrix and FORM CHROMOSOMAL LOOPS the mars the matrix attachment regions bind to specific particular proteins within the nuclear matrix, specific proteins composing the nuclear matrix and thus form chromosomal loops WHY IS THE ATTACHMENT OF THE RADIAL LOOPS TO THE NUCLEAR MATRIX IMPORTANT the attachment of the radial loops to the nuclear matrix is v important the attachment of the radial loops to the nuclear matrix is v important bc in ADDITION TO COMPACTION which is one of the v necessary functions of the nuclear matrix in addition to compaction, the nuclear matrix is also responsible for the ORGANIZATION OF CHROMOSOMES WITHIN THE NUCLEUS, thus showing us the importance of the attachment of radial loops to the nuclear matrix the attachment of radial loops to the nuclear matrix is important bc the attachment of radial loops to the nuclear matrix assists the nuclear matrix in its function other than DNA compaction, which is the organization of chromosomes within the nucleus each chromosome within the cell nucleus is located in and designated a DISCRETE CHROMOSOME TERRITORY each chromosome within the cell nucleus is located in and designated a DISCRETE CHROMOSOME TERRITORY there have been studies conducted by Thomas Cremer , Christoph Cremer and other researchers these studies conducted by Thomas Cremer, Christopher Cremer, and others revealed that these discrete CHROMOSOME TERRITORIES that each chromosome within the nucleus is assigned and designated CAN BE VIEWED these discrete chromosome territories that each chromosome within the nucleus is assigned and designated CAN BE VIEWED these discrete chromosome territories, the nuclear matrix's method by which it organizes the chromosomes within the nucleus CAN BE VIEWED when interphase cells are EXPOSED TO MULTIPLE FLUORESCENT MOLECULES when interphase cells are exposed to multiple fluorescent molecules, these discrete chromosome territories can be viewed these discrete chromosome territories can be viewed when cells in interphase are exposed to MULTIPLE FLUORESCENT MOLECULES these discrete chromosome territories are viewable in the particular circumstance of cells in interphase being exposed to MULTIPLE FLUORESCENT MOLECULES that RECOGNIZE SPECIFIC PARTICULAR SEQUENCES ON PARTICULAR CHROMOSOMES these discrete chromosome territories are viewable in the particular specific circumstances of cells undergoing interphase being exposed to multiple fluorescent molecules that can detect specific sequences specific genetic sequences on particular specific chromosomes an experiment done in order to view discrete chromosome territories: THERE WAS AN EXPERIMENT DONE

genetic mapping

the purpose of genetic mapping the purpose of genetic mapping the purpose genetic mapping the purpose of genetic mapping what is the purpose of genetic mapping the purpose of genetic mapping the purpose of genetic mapping the purpose of genetic mapping genetic mapping is also known as chromosome mapping genetic mapping is also known as chromosome mapping genetic mapping is also known as chromosome mapping genetic mapping/chromosome mapping is a technique that is utilized in order to determine the linear order/location and distance of separation among genes that are linked to one another on the same chromosome genetic mapping/chromosome mapping is a technique utilized in order to determine the linear order and the distance of separation among genes that are linked to one another along the same chromosome chromosome mapping/genetic mapping is utilized in order to determine the linear order/location and distance of separation of genes that are linked to one another on the same chromosome there is a figure that showcases the simplified genetic map of Drosophila melanogaster this simplified genetic map depict the locations of many different genes along the individual chromosomes this simplified genetic map depicts the locations of many different genes along the individual chromosomes the simplified genetic map depicts the locations of many different genes along the individual chromosomes the simplified genetic map depicts the locations of many different genes along the individual chromosome each gene has its own locus what is the locus the locus, each gene has its own locus the locus is the site where the gene is found within a particular chromosome for example the gene that is designated brown eyes, bw, which impacts and influences eye color is located near one end of chromosome 2, therefor is has a locus, the site where the gene is found within a particular chromosome near the end of chromosome 2 the gene that is designated black body (b) and affects and impacts body color, is found near the middle of the same chromosome, it is found near the middle of the same chromosome and therefore has its locus at this location why is genetic mapping useful? genetic mapping is useful bc it allows geneticists to understand and comprehend the overall complexity and genetic organization of a particular species genetic mapping is useful bc it allows geneticists to understand and comprehend the overall complexity and genetic organization of a particular species genetic mapping is utilized in order to understand the overall complexity and genetic organization of a particular species genetic mapping is utilized in order to understand the overall complexity and genetic organization of a particular species the genetic map of a species portrays the underlying basis for the inherited traits that an organism displays in some cases, the known locus of a gene within a genetic map can help molecular geneticists to clone that particular gene due to the locus of this gene being known, the gene can be cloned by molecular geneticists, and thereby through the cloning of this gene, obtain and acquire greater information about the molecular features of that gene that was cloned genetic maps are also useful from an evolutionary standpoint

incomplete penetrance and variable expressivity- explanations for these terms

the range of phenotypes and the ways in which they can be defined by their penetrance in a population or expressivity in an individual is attributed to: -environmental influences -effects of modifier genes in which one or more genes alters the phenotypic effects of another gene (a different phenotypic trait that another gene codes for, so the presence of this modifier gene means that the phenotypic trait being coded for by a different gene will be impacted and altered, this modifier gene is influencing another gene and the phenotypic trait that that gene codes for)

experiment done in order to reveal the REPEATING NUCLEOSOME STRUCTURE

the repeating nucleosome structure was revealed by THE DIGESTION OF THE LINKER REGION the model of nucleosome structure, the modern model of nucleosome structure was ORIGINALLY PROPOSED BY ROGER KORNBERG he proposed this model of the nucleosome structure in 1974 what did Roger kornberg base his proposal of the nucleosome structure on? how did he propose what the nucleosome structure was and is? he proposed his potential structure for nucleosomes BASED ON SEVERAL OBSERVATIONS he based his proposal of nucleosome structure on SEVERAL OBSERVATINS there were previously implemented biochemical experiments these previously implemented biochemical experiments had shown that CHROMATIN CONTAINS A RATIO OF ONE MOLECULE OF EACH OF THE FOUR CORE HISTONES previously implemented biochemical research and experiments showcased the confirmed results that chromatin contains a ratio of one molecule of each of the four histones a 1:1:1:1 ratio recall that the four core histones that the chromatin had a ratio of one molecule to one molecule to one molecule to one molecule of were H2A, H2B, H3, and H4 these previously implemented biochemical experiments showed that chromatin contained a ratio of one molecule of each of these four histone proteins H2A, H2B, H3, and H4 EVERY 100 BASE PAIRS OF DNA every 100 base pairs of dna, chromatin was found through the implementation of biochemical experiments to have a ratio of one molecule of each of the four core histone proteins previously implemented biochemical experiments also confirmed the fact that in chromatin, there was 1 H1 histone, one linker histone per every 200 base pairs in these previously implemented biochemical experiments, it was confirmed that within chromatin, there is 1 H1 histone, 1 linker histone found per every 200 base pairs of DNA in addition to these aforementioned discovers of there being one octamer of histones every 100 base pairs of a DNA double stranded molecule, and there being 1 linker histone, 1 H1 histone every 200 base pairs of a DNA double stranded molecule, there was a discovery having to do with PURIFIED CORE PROTEINS PURIFIED CORE HISTONE PROTEINS WERE FOUND TO BIND TO EACH OTHER VIA SPECIFIC PAIRWISE INTERACTIONS purified core histone proteins were found to bind to one another via specific pairwise interactions via specific pairwise interactions, purified core histone proteins were found to bind to one another there were subsequent x ray diffraction studies implemented, and these x ray diffraction studies showed that chromatin is COMPOSED OF A REPEATING PATTERN OF SMALLER UNITS implemented subsequent x ray diffraction studies showcased that CHROMATIN IS COMPOSED OF A REPEATING PATTERN OF SMALLER UNITS chromatin is composed of a repeating pattern of smaller units, chromatin is composed of a REPEATING PATTERN OF SMALLER UNITS, this was confirmed by implemented x ray diffraction studies, these implemented x ray diffraction studies showcased that chromatin is COMPOSED OF A REPEATING PATTERN OF SMALLER UNITS these implemented x ray diffraction studies showcased that chromatin is composed of a REPEATING PATTERN OF SMALLER UNITS electron microscopy implemented on chromatin fibers showcased a new discovery it was discovered that chromatin fibers have a diameter of 11nm, this was discovered by the implementation of electron microscopy all of these aforementioned biochemical experiment implements, x ray diffraction studies, etc. LED ROGER KORNBERG to propose a model for the nucleosome Roger kornberg proposed the following model for the structure of the nucleosome he proposed a model in which THE DNA DOUBLE HELIX IS WRAPPED AROUND AN OCTAMER OF CORE HISTONE PROTEINS Roger kornber proposed a nucleosome model in which he dna double helix molecule is wrapped around an octamer of core histone proteins including the linker dna region (considering the the length of the DNA wrapped around the histone octamer tends to be anywhere from 146 to 147 base pairs) the amount of dna in a nucleosome consists of 200 base pairs of DNA Markus Noll decided to test out the model of the nucleosome proposed by Roger Kornberg, the model proposing that a nucleosome consists of a double stranded dna molecule wrapping itself around an octamer of histone proteins, and the length of the DNA, including the linker region connected to the nucleosome adding up to 200 base pairs Markus Noll tested Roger Kornberg's proposal of the nucleosome model by DIGESTING CHROMATIN WITH DNase I he digested chromatin with DNase I DNase I is an enzyme that cuts the DNA backbone DNase I is an enzyme that cuts the DNA backbone then Markus Noll, after have the chromatin digested by DNaseI which cuts the DNA backbone, ACCURATELY MEASURED THE MOLECULAR MASS OF THE DNA FRAGMENTS through the usage of gel electrophoresis through the implementation of gel electrophoresis, Markus Noll accurately measured the molecular mass of the dna fragments that came about due to the digestion of chromatin by DNase I, an enzyme that cuts the DNA backbone Noll assumed that the liner region of DNA is more accessible to DNase I the enzyme that can digest chromatin and cuts the DNA backbone, and therefore bc this linker region of DNA is more accessible to DNase I, he presumed that the enzyme is more likely to make cuts in the linker region than in the 146 base pair DNA double stranded molecule sequence that is wrapped around the histone octamer therefore, if DNase I would be more inclined to make cuts in the dna backbone of the linker region than the DNA double helix molecule region wrapped around the histone octamer, when incubation with DNase I OCCURRED, incubation with DNase I would be expected to make cuts in the linker regions only, and therefore result in DNA fragments spanning about 200 base pairs the size of the DNA fragments were expected to somewhat vary, because the linker regions length is not always consist, so the ultimate length of the DNA fragments produced due to cuts in the variegated length linker regions would also differ the cut in the linker region by the DNase I may also occur in different sites along the linker region, also contributing to the distinct and different lengths found in the dna fragments produced from the incubation of this DNA by the DNase I what was Markus Noll's experimental protocol in order to test Roger Kornberg's proposed nucleosome model? his protocol was to begin with nuclei collected from rat liver cells he incubated these nuclei collected from rat liver cells he incubated these nuclei collected from rat liver cells with LOW MEDIUM OR HIGH CONCENTRATIONS OF DNaseI then the DNA was extracted from the nuclei incubated with varying amounts of DNaseI how was the DNA extracted from the nuclei of the rat liver cells that were incubated with varying amounts of DNase I? the nuclear membrane of the nucleus was dissolved with DETERGENT the DNA within the nuclei of these rat liver cells was extracted through the usage of the ORGANIC SOLVENT PHENOL after the organic solvent phenol was utilized in order to extract the DNA from the nuclei of the rat liver cells into an aqueous phase the DNA was then loaded onto an agarose gel this agarose gel SEPARATED THE DNA FRAGMENTS that resulted from the incubation of these nuclei with varying amounts of DNaseI,, and separated these DNA fragments according to their molecular mass THE DNA FRAGMENTS WITHIN THE AGAROSE GEL were stained with a UV SENSITIVE DYE this UV sensitive dye that the dna fragments (recall that these dna fragments that were loaded onto the agarose gel and separated and sorted by their molecular mass resulted from the incubation of the rat liver cells' nuclei with varying amounts of DNaseI) were stained with was the UV SENSITIVE DYE ETHIDIUM BROMIDE this uv sensitive dye ethidium bromide that the dna fragments were stained with MADE IT POSSIBLE TO VIEW THE DNA FRAGMENTS UNDER UV ILLUMINATION the uv sensitive dye that the dna fragments loaded on the agarose gel were stained with, ethidium bromide, MADE IT POSSIBLE TO VIEW THE DNA FRAGMENTS UNDER UV ILLUMINATION the hypothesis of this experiment was to seek the understanding of the proposed nucleosome model, the beads-on-a-string model for the chromatin structure according to this proposed model, when DNA is incubated with DNaseI, the DNase I should preferentially cut the DNA in the easily accessible linker region, resulting in DNA fragments that are about 200 base pairs in length looking at the photograph of the gel, the sample of DNA that was incubated with a high concentration of DNaseI was digested by DNaseI into chromosomal fragments that were about 200 base pairs in length all of the DNA within this sample that was incubated with a high concentration of DNase, was found on the gel in fragments of 200 base pairs the DNase I had preferentially cut all of the DNA at its linker regions, the more easily accessible region of DNA, and this resulted in DNA fragments that were about 200 base pairs in length this result was predicted by the beads on a string model proposed by Robert Kornberg it was predicted that if the model the beads on a string model proposed by Robert Kornberg was indeed true then when DNA was incubated with DNaseI, came into contact with DNAaseI, the DNase I would preferentially cut in the easily accessible linker region of this nucleosome model, resulting in DNA fragments that were 200 base pairs in length at lower DNase I concentrations in samples that were exposed to lower DNase I concentrations, there were DNA fragments of various sizes that were observed, DNA fragments ranging from 200 to 400 to 600 base pairs long how do we explain the presence of these longer dna fragments? why did these longer dna fragments occur in the DNA sample exposed to lower concentrations of DNaseI? the occurred, because there are occasional linker regions that remain uncut at lower DNase I concentrations these occasional linker regions remained uncut at lower DNase I concentrations bc DNase enzymes preferentially cut at the linker regions of DNA, usually resulting in 200 base pair long DNA fragments, but in lower concentrations of the DNAase I enzyme there may be linker regions completely skipped over, therefore resulting in longer DNA fragments due to the DNase I neglecting to cut particular linker regions for example if one linker region was not cut by the DNase I enzyme due to a low concentration of DNase I enzyme, then a DNA piece would contain two nucleosomes and 2 linker regions and consist of 400 base pairs, be 400 base pairs in length if there were two consecutive linker regions not cut, then there would be three nucleosomes, containing about 600 base pairs of DNA these above results strongly supported, confirmed, and verified the nucleosome structure proposed by Roger Krogner for the structure of chromatin

yeast, chlamydomonas, and extranuclear inheritance

the research done by Carl Correns and other researchers concluded that some traits (ie leaf pigmentation) follow non-Mendelian patterns of inheritance, and are not inherited in a classic way adhering to established Mendelian law (and it was later understood that this non-Mendelian pattern of inheritance found in the inheritance of leaf pigmentation is due to maternal inheritance, where the mother is the sole genetic determinant of the genotype of the offspring and therefore the phenotype) these studies that were conducted understood that particular traits such as leaf pigmentation did not follow traditional, established Mendelian patterns of inheritance, but they did not conclude that the maternal inheritance phenomenon that causes this particular non-Mendelian pattern of inheritance is due to the genetic material found within organelles (rather than genetic material found within the nucleus) there was further progress made into the investigation and understanding of extranuclear inheritance, and it was made due to the implementation of genetic analysis of various eukaryotic microorganisms the microorganisms that researchers genetically analyzed were yeast and algae researchers isolated and designated particular mutant phenotypes within these microorganisms, such as yeast and algae, particular mutant phenotypes that specifically affected the organelles- mitochondria and/or chloroplasts yeasts and molds functioned as model eukaryotic organisms for investigating the ways in which mitochondria is inherited yeast and molds functioned as model organisms for this research during the 1940s and 1950s one of the function of mitochondria is to synthesis energy in the form of ATP for cells to utilize in order to carry out their various processes therefore (due to this very important known function of mitochondria), it was understood that any mutations that resulted in defective nonfunctional mitochondria would also result in cells (those containing these defective mitochondria) to grow at a much slower rate (due to the defectiveness of the organelle that provides them with energy) a researcher named Boris Ephrussi and his colleagues looked at mutations within Saccharomyces cerevisiae that had this particular phenotype, of unusually slow cell growth the mutants that Boris Ephrussi and his colleagues found were designated as petites petites was their designation as this term accurately described how these mutant cells formed small colonies on agar plates (due to unusually slow growth rate due to defective, mutated mitochondria), as opposed to the wild type, normal strains of cells that were able to and did form large colonies on agar plates (due to their possession of normal functional mitochondria and therefore a normal growth and proliferation rate) in the above experiments, there was biochemical and physiological evidence indicating something about the petites the indication was that the petites were not able to proliferate at a normal rate because these mutant had defective, nonfunctional mitochondria how did they discover that the slow proliferation was due to the absence of functional mitochondria? the researchers saw that the petite mutants were unable to grow when they were trying to operate off of an energy source that require the metabolic activity and function of mitochondria in order to be provided and utilized by the cells (energy in the form of ATP is the way in which cells use energy, and mitochondria synthesize energy in the form of ATP) however, small (albeit slow growing) colonies could form on plates when these cells were grown on sugars that could be metabolized and utilized by the glycolytic pathway, a pathway that functions and takes place outside of the mitochondria and still provides the cell with energy without the need for the functionality of the mitochondria (which works well if the mitochondria is defective) Boris Ephrussi and his colleagues were able to look at yeast cells as well yeast cells esxist in two mating types these two mating types that yeast cells exist in include a and alpha Boris Ephrussi mated a wild-type strain to his petite mutants (that had slow proliferation rates) when he implemented various genetic analyses, Boris Ephrussi realized that petit mutant inheritance functioned in a variety of ways

experiment testing and verifying that adult female mammals contain 1 X chromosome that has been permanently inactivated within all of their somatic cells

the steps: 1. the researchers mice the tissue of the adult heterozygous female organism in order to collect a conglomeration of individual somatic cells from this organism (the tissue is composed of a multitude of cells, and mincing is done to the tissue in order to separate all of these cells into their own individual entities) 2. the researchers then grow the cells collected in a liquid growth medium (place them in a liquid growth medium and allow them all to proliferate due to mitosis) they then sparsely plate these cells that were grown and proliferated within the liquid growth medium onto a solid growth medium (so now the cells that proliferated within the liquid growth medium for several days are on a solid growth medium, as they have been sparsely plated onto this solid growth medium after proliferation) the cells sparsely plated on this solid growth medium then proliferate through mitosis cellular division in order to form a colony/clone of a multitude of cells 3. the researchers then find 9 isolated clones and grow these colonies/clones within liquid cultures so they can proliferate further (recall that within colonies/clones, all of the cells stem from one origin cell, and are therefore identical to the original cell and are all identical to one another, having been replicated from that origin cell to proliferate into a colony) 4. the researchers then take the cells from the colonies/clones grown within the liquid culture they then lyse (burst these cells) in order to acquire the G-6-PD proteins within each of these cells, and subject them to gel electrophoresis in order to see and determine which cells contain the slow enzymes and which cells contain the fast enzyme the researchers, in order to control confounding variables, also lyse/burst the cells from step 1 that are simply from the mixed collection of somatic epithelial cells collected from the adult female heterozygous organism, and subject them to gel electrophoresis in order to determine which cells have the fast enzyme and which ones have the slow enzyme the data of this experiment: in the lane examined, there were bands corresponding to both fast and slow G-6-PD enzymes the proteins obtained from the clones/colonies created from the original mixture of epithelial cells were placed in lanes 2-10 each individual clone was a population of identical cells that were obtained from a single origin epithelial cell due to the fact that all of the original epithelial cells (from which all the clones were proliferated individually to form identical groups of cells identical to the one cell they all originated from) were collected from an adult female, the Lyon hypothesis was utilized in order to propose the notion that every one of the somatic epithelial cells has an inactivated X chromosome, and from somatic epithelial cell to somatic epithelial cell, the X chromosome that is inactivated can change depending on which epithelial origin cell each epithelial cell originated from the X chromosome that is inactivated in each individual somatic epithelial cell depends upon the X chromosome that was inactivated in the origin cell that the given somatic epithelial cell originated from the origin cell would pass the trait coded for by its active X chromosome onto its offspring an example showcasing this phenomenon of X-inactivation is if there is an epithelial cell with an inactivated X chromosome this inactivated X chromosome, if active would could for the fast G-6-PD enzyme if this cell was allowed to undergo mitosis and proliferate in a growth medium, then all of the cells formed from the original proliferation of this original epithelial cell would have this same X chromosome (coding for the fast G-6-PD enzyme) inactivated the original epithelial cell and the clone created from this cell would all have the active X chromosome coding for the slow G-6-PD enzyme all of the nine clones had the allele coding for either the fast or slow G-6-PD enzyme, but not both all nine clones has a whole either expressed (from clone to clone) either the fast G-6-PD enzyme or the slow one the results and data gathered were consistent with the hypothesis of X inactivation of one X chromosome occurring in each individual cell, and that from cell to cell during proliferation, the X chromosome that is inactivated is maintained throughout all the generations stemming from a particular cell

population genetics

the study of population genetics concerns itself with genetic variation, and the contributes it makes to/the role it plays in evolution it is a study that became popular in the first few decades of the 20th century, so the 1900s this field of study connected the findings of Mendel and Darwin to one another looking at Mendel specifically, he provided a perspective understanding the nature of genes and how these genes and therefore traits are passed from parent to offspring looking at Darwin- he provided a natural explanation (nature's role in) the variation observed among species, how members of the same species can present differently morphologically, physiologically, behaviorally population genetics has developed mathematical theories in order to explain the prevalence of certain alleles, particular traits within a certain population it understands the relationship bw the presence of these genes and the influence of nature there is a relationship bw genetic variation and the environment an organism is in (And how that affects genetic variation) that is studied heavily by population genetics

sum rule

the sum rule states that the probability that 1 or 2 more mutually exclusive events will occur is equal to the sum of the individual probabilities of the events (the events are mutually exclusive to one another, so if one happens, the other can't happen, that is why you are able to add their individual probabilities together) an example is a cross bw two mice, both mice are heterozygous for genes affecting the ears and tail (so for both characters, they have the dominant and recessive allele in their allelic combinations) look at the example in notes

the three dimensional structure of DNA and RNA

the three dimensional structure of dna the three dimensional structure of dna within chromosomes requires additional folding and association with proteins the three dimensional structure of dna that is found within chromosomes, the three dimensional structure of dna that is found within chromosomes requires additional folding and association of the dna with proteins the three dimensional structure of dna that is found within chromosomes requires additional folding and association of the dna with proteins in order to fit within a living cell, the long, linear, and double helical structure of chromosomal dna must be extensively compacted into a particular 3 dimensional conformation in order for the chromosomal dna to fit within a living cells, where the nucleus has a diameter of 2-4 nm, the long, linear, double-helix shaped chromosomal dna must be extensively compacted and packaged into a particular 3 dimensional conformation in order for this long, linear, double helix shaped chromosomal dna to properly fit within a living cell with the aid of DNA binding proteins, proteins that specifically bind to dna, with the aid of these proteins that specifically bind to dna, the double helix shape of the dna, the double helix shape of the chromosomal dna becomes greatly twisted and fold the aid of these proteins, with the aid of these dna binding protiens, with the aid of these proteins that bind to dna, with the aid of these proteins that bind to dna, such as histone proteins (histone proteins are of course heavily involved in compaction) with the assistance of these dna binding proteins, the double helix becomes greatly twisted and folded and therefore highly compacted the relationship bw the double helix and the compaction that occurs within a eukaryotic chromosome rna molecules are composed of strands that fold into specific structures rna molecules are composed of strands that fold into specific structures rna molecules are composed of strands that fold into specific structures rna molecules are composed of strands that fold into specific strucrures rna structure rna structure bears many similarities to dna structure rna structure bears many similarities to dna structure rna structure bears many similarities to dna structure the structure of an ran strand bears many similarities to dna structure, rna structure is much like dna structure an rna strand is much like a dna strand strands of rna are typically several hundred or several thousand nucleotides strands of rna are typically several hundred or several thousand nucleotides in length strands of rna are typically several hundred or several thousand nucleotides in length strands of rna are typically several hundred or several thousand nucleotides in length strands of rna are typically several hundred or several thousand nucleotides in length this is much shorter than chromosomal dna strands of rna are typically several hundred or several thousand nucleotides in length this is much shorter than chromosomal dna when rna is produced during transcription, the dna is utilized as a template in order to make a copy of single stranded rna during transcription, when rna is produced, the dna is utilized as a template in order to make a copy of single stranded rna during transcription when rna is produced the dna is utilized as a template in order to make a copy of single stranded rna in most cases, only one of the two dna strands is used as a template for rna synthesis for the synthesis of single stranded rna in most cases only one of the two dna strands is used as a template for rna synthesis for the synthesis of single stranded rna in most cases only one of the two dna strands is used as a template for rna synthesis, for the synthesis of single stranded rna therefore, only one complementary strand of RNA is usually made therefore only one complementary strand of RNA is usually made therefore only one complementary strand of RNA is usually made therefore only one complementary strand of RNA is usually made therefore only one complementary strand of RNA is usually made therefore only one complementary strand of RNA is usually made therefore only one complementary strand of RNA is usually made therefore only one complementary strand of RNA is usually made nevertheless relatively short sequences within one RNA molecule or bw two separate RNA molecules nevertheless relatively short sequences within one RNA molecule or bw two separate RNA molecuels can form double stranded regions nevertheless relatively short sequences within one RNA molecule or bw two separate RNA molecules can form double stranded region therefore only one complementary strand of RNA is usually made nevertheless relatively short sequences within one RNA molecule or bw two separate RNA molecules can form double stranded regions nevertheless relatively short sequences within one RNA molecule or bw two separate RNA molecules can form double stranded regions nevertheless relatively short sequences within one RNA molecule or bw two separate RNA molecules can form double stranded regions nevertheless relatively short sequences within one RNA molecule or bw two separate RNA molecules can form double stranded regions, despite only one complementary RNA strand being created due to transcription the helical structure of RNA molecule the helical structure of RNA molecules is due to the ability of the complementary regions of the RNA molecule to form base paris bw A and U and bw G and C the helical structure of RNA molecuels is due to the ability of the complementary regions of the RNA molecule to form pairs bw A and U and bw G and C this base pairing allows short segments to form a double stranded region this base pairing bw the nitrogenous bases adenine and uracil and the nitrogenous bases guanine and cytosine with complementary regions of a single stranded rna molecule allows short segments of the RNA molecule to form a double stranded region the helical structure of RNA molecules is due to the ability of complementary regions of the RNA molecule to form base pairs bw the nitrogenous bases adenine and uracil and the nitrogenous bases guanine and cytosine the helical structure of RNA molecules is due to this where the pairing bw adenine and uracil and guanine and cytosine with complementary regions of the rna strand can create short double stranded regions short segments of rna are able to form a double stranded region different types of structural patterns of rna are possible this includes bulge loops internal loops multibranched junctions stem loops- also called hairpins these structures of bulge loops, internal loops, multibranched junctions, step loops (also called hairpins), these structures that rna can form these conformations that rna can take on, these structures contain regions of complementarity these regions of complementarity are punctuated by regions of noncomplementarity these structures contain regions of complementarity and regions of noncomplementarity these structures contain regions of complementarity punctuated with regions of noncomplementarity the complementary regions are held together by hydrogen bonds the complementary regions of these structures are held together by hydrogen bonds the noncomplementary regions of these structures have their bases projecting away from the double stranded region formed by the hydrogen bonds occurring bw the complementary regions there are many factors that contribute to the structure of RNA molecules these factors that contribute to the structure of RNA molecules include: the base paired double stranded helices, the regions of the double helix formed by short segments of compleemntary rna molecule regions the stacking bw bases hydrogen bonding bw bases hydrogen bonding bw the backbone regions in addition to this, there are even more factors contributing to the structure of rna interactions with ions small molecules large proteins interactions with ions, small molecules, and large proteins may contribute and influence rna structure interactins with ions, small molecules, and large proteins may contribute and influence rna structure interactions with ions, small molecules, and large proteins may contribute and influence rna structure what is tRNAphe tRNAphe is a tRNA molecule, this tRNA molecule carries the amino acid phenylalanine tRNAphe is a tRNA molecule, this tRNA molecule carries the amino acid phenylalanine it was the first naturally occurring rna molecule to have its structure elucidated tRNAphe was the first naturally occurring rna molecule to have its structure elucidated tRNAphe was the first naturally occurring rna molecule to have its structure elucidated and established, this is a tRNA molecule that carries the amino acid phenylalanine tRNAphe was the first naturally occurring rna molecule to have its structure elucidated and constructed verifiably and established, this is a tRNA molecule that carries the amino acid phenylalanine this rna molecule, tRNAphe has several double stranded and single stranded regions this rna molecule, tRNA phe has several double stranded and single stranded regions this rna molecule, tRNA phe has several double stranded and single stranded regions this rna molecule, tRNAphe has several double stranded and single stranded regions RNA double helices are antiparallel to one another, within a double helix region of an rna molecule RNA double helices are antiparallel to one another within a double helix region of an rna molecule, the strands composing, the short complementary regions of the rna molecule constructing this double stranded region are running antiparallel to one another, one running in a 5 prime to 3 prime direction, the other running in a 3 prime to 5 prime direction RNA double helices, regions of an rna molecule that are in the form of a double helix are also right handed, these rna double helices are in a right handed conformation and they have 11 to 12 base pairs per turn Rna double helices regions of an rna molecule creating a double helix are right handed and have 11 to 12 base pairs per turn Within a living cell, the various regions of an rna molecule fold and interact with one another in order to produce the three dimensional structure Within a living cell, that various regions of an rna molecule interact with one another fold and interact with one another in order to produce the 3 dimensional structure The folding of RNA into a 3 dimensional structure is important for its function The folding of RNA into a 3 dimensional structure is important in regards to the function of RNA A tRNA molecule has 2 key functional sites A tRNA molecule has 2 key functional sites A tRNA molecule has 2 key functional sites A tRNA molecule has 2 key functional sites These two key functional sites of the tRNA molecule These two key functional sites of the tRNA molecule are an ANTICODON and a 3 PRIME ACCEPTOR SITE These two key functional sites of the tRNA molecule These two key functional sites of the tRNA molecule are an ANTICODON and a 3 PRIME ACCEPTOR SITE These two key functional sites of the tRNA molecule, these two key functional sties of the tRNA molecule, the anticodon and the 3 prime acceptor site The anticodon and the 3 prime acceptor site These play important roles in translation In a folded tRNA molecule, in a folded tRNA molecule with an anticodon and a 3 prime acceptor site, two key functional sites of a tRNA molecule, in a folded tRNA molecule, the anticodon and the 3 prime acceptor site are exposed on the surface of the tRNA molecule in a folded tRNA molecule, and they are therefore to their exposure, the exposure of the anticodon and the 3 prime acceptor site on the surface of the tRNA molecule, can perform their roles There are many other examples that are known in which RNA folding, the folding of an RNA molecule into a 3 dimensional structure is extraordinarily important and key to the structure and the function of the tRNA molecule These include, these examples include the folding of ribosomal rnas, (rRNAs) Ribosomal RNAs are important components of the structure of ribosomes Ribozymes, they are RNA molecules with catalytic function

Mendel's law of segregation

the two copies of a gene (alleles) segregate/separate from one another during the transmission of genes from parent to offspring this is why you will only find a single copy of any given gene in a gamete (and therefore when gametes fuse you will find 2 copies of the given gene, and depending on whether they are the same or different will determine how the offspring presents in regards to that character) during fertilization, two gametes (each containing a variant of the gene, they could contain the same one or different) combine randomly, leading to random allelic combinations

gene interaction

the understanding of how a multitude of genes and alleles within those genes can interact in order to affect a single trait

X inactivation and molecular expression

the way that particular genes are expressed molecularly influences the process of X inactivation there is the expression of a particular gene within the Xic region on an X chromosome that is required in order for the X chromosome with the Xic region with this particular gene expressed to be compact and turned into a Barr body so in order for an X chromosome to turn into a body, it must have a Xic region with a specific gene expressed on it the gene that is required to be expressed within the Xic region on the x chromosome in order for that X chromosome to be inactivated is designated as Xist Xist stands for X-inactive specific transcript Xist was discovered in 1991 the Xist gene on the inactivated chromosome is active it is unusual that the Xist gene on the inactivated chromosome is active, because once the X chromosome has been inactivated, all of the genes upon the X chromosome are silenced however the Xist gene used to be active the product of this Xist gene is an RNA molecule that does not encode a protein the Xist RNA functions in the manners that it coats the entirety of the X chromosome and inactivates it, silencing the rest of the genes on this chromosome there is a second gene found within the Xic region of the X chromosome this second gene is designated as Tsix this gene plays a role in preventing the X chromosome from being inactivated how does this occur? how is x inactivation implemented and coded for by the Xist gene prevented by the Tsix gene? the Xist and Tsix genes are overlapping and transcribed in opposite directions so these two genes overlap, and when the Xist and Tsix genes are transcribed, they are transcribed in opposite directions if the Tsix gene is expressed, then the X-inactivation coded for by the Xist gene is not expressed the expression of the Tsix gene prevents the expression of the Xist gene, which codes for X-inactivation (inactivation of an X chromosome) on an active X chromosome (an X chromosome that is activated, and therefore all of the genes on this chromosome are expressed), the Tsix gene is expressed coding for the activation of the X chromosome (or rather coding against the inactivation of the X chromosome) that it is on on an inactive X chromosome (an X chromosome that is inactivated, and therefore all of the genes on this chromosome are inactivated and therefore not expressed), the Xist gene is expressed, coding for the inactivation of the X chromosome and therefore the inactivation of all of the genes on this chromosome, and the Tsix gene that would code against inactivation is not expressed researchers have studied heterozygous females that carry a normal Tsix gene coding for chromosome activation on one X chromosome (that is subsequently active) and a defective, mutant Tsix gene on the other X chromosome this mutant Tsix gene is not expressed to code against inactivation, and the X chromosome that this defective, mutant Tsix gene is on is inactivated

environmental conditions impacting phenotypic expression- phenylketonuria

their is a powerful relationship bw environment and phenotypic expression in regards to the human genetic disease phenylketonuria (PKU) phenylketonuria is an autosomal (coded for on a non-sex chromosome) that is caused by a defect in a gene this gene when functioning normally (non mutated) codes for the enzyme phenylalanine hydroxylase this enzyme phenylalanine hydroxylase coded for by the normal alleles of the autosomal gene metabolizes the amino acid phenylalanine when there is a homozygous recessive individual, containing two recessive alleles for the mutated gene, the individual does not have a functioning phenylalanine hydroxylase enzyme, and therefore is unable to properly metabolize the amino acid phenylalanine when an individual that is homozygous for phenylketonuria (two recessive alleles coding for this condition) is given a standard diet consisting of phenylalanine (a lot of protein-rich foods contain phenylalanine, and protein rich foods are considered a staple of any individual's diet), the individuals impacted by phenylketonuria manifest a host of detrimental traits including: -mental impairment -underdeveloped teeth -foul-smelling urine however, if the individual that is homozygous recessive for phenylketonuria is given restrict diet, where all foods containing phenylalanine are eliminated, then the individual is able to develop normally, and will not express any of these hallmark and debilitating traits associated with phenylketonuria since the 1960s, there have been testing methods developed that are able to determine whether or not an individual has enough of the phenylalanine hydroxylase enzyme or not these tests can be utilized in order to determine whether or not infants have PKU if an individual is found to have PKU, then their diets will be modified to eliminate phenylalanine in order to ensure that the harmful effects of phenylalanine ingestion (and lack of metabolization due to the absence of the phenylalanine hydroxylase enzyme) never come to lights due to government legislation for PKU testing, more than 90% of infants within the US are tested for PKU it prevents a lot of preventable human suffering and is very cost effective the cost effective portion: in the United States, the annual cost of PKU testing is estimated to reach about a couple million dollars the cost treating individuals severely affected by phenylketonuria (due to lack of adequate PKU testing at birth)) would be hundreds of millions of dollars

the process of x inactivation

there are 3 phases of X inactivation - initiation - spreading - maintenance during the initiation phase: this process of initiation (that is one of the phases that composes x inactivation) occurs during embryonic development (the embryo developing) during the initiation phase, one of the X chromosomes in the pair of the X chromosomes remains active, while the other X chromosome is chosen to be inactivated how is one X chromosome chosen to be inactivated? it is not completely understood how one X chromosome is chosen to be inactivated, but the proposed notion is that the choice of which X chromosome is inactivated occurs due to the relationship bw gene expression of the Xist gene coding for inactivation and the Tsix gene coding for activation spreading phase: the chosen X chromosome (that was chosen during the process of initiation) is inactivated the spreading phase where the X chromosome is inactivated requires the expression of the Xist gene, that codes for the inactivation of the X chromosome the Xist RNA the product that is coded for by the Xist gene spreads all over the chosen X chromosome, coats it, and recruits other proteins that promote the process of compaction, which will compact and condense the X chromosome and turn it into a Barr body the compaction of DNA that is implemented by Xist RNA that recruits proteins that promote the process of compaction the process of compaction itself, the physical process of compaction involves: DNA methylation the modification of histone proteins this entire process of DNA compaction is described in Chapter 10 why is the spreading phase designated as the spreading phase? it is called the spreading phase bc inactivation of the X chromosome begins near the Xic region of the X chromosome and spreads in both directions along the X chromosome, so the inactivation begins after the initiation and spreading phases occur for a particular X chromosome so during the initiation phase has occurred and the X chromosome to be inactivated has been chosen, and during the spreading phase the chosen X chromosome has been inactivated due to the Xist RNA product coded for by the Xist gene coating the X chromosome and recruiting proteins that promote compaction, the now inactivated X chromosome is maintained as a Barr body for all future cell divisions within all the cells from this cell with an inactivated X chromosome, all the cells that proliferate from this one with a particular X chromosome inactivated will have the same X chromosome inactivated during mitosis and cell replication, the Barr body becomes replicated, and both of the copies of this inactivated X chromosome remain inactive so the two daughter cells both have X chromosomes that are inactivated this inactivation of an X chromosome is maintained from the embryonic development stage all the way to maturation and adulthood

prokaryotes

there are distinctive, demarcated, memorable differences bw bacterial and eukaryotic species PROKARYOTES INCLUDE BACTERIA AND ARCHAE bacteria and archaea are referred to as prokaryotes, bacteria and archaea are considered prokaryotes why are prokaryotes (specifically bacteria and archaea) considered prokaryotes, and what does that mean? prokaryotes are called prokaryotes bc the designation itself its a word from the Greek- prokaryote means PRE NUCLEUS, prior to having a nucleus prokaryotes are designated as such because their chromosomes are not contained within a membrane bound nucleus within the cell prokaryotes have chromosomes, but they are not stored within a membrane bound nucleus where are the chromosomes located then, if they are not found within a membrane bound nucleus (RECALL THAT A PROKARYOTIC CELL DOES NOT HAVE A MEMBRANE BOUND NUCLEUS) PROKARYOTES what form does their non nuclear membrane bound DNA come in? prokaryotes usually have a SINGLE TYPE OF CIRCULAR CHROMOSOME this single type of circular chromosome is located in a region of the cytoplasm designated as the NUCLEOID SO THE SINGLE TYPE OF CIRCULAR CHROMOSOME Is stored in a region of the cytoplasm designated as the NUCLEOID THE CYTOPLASM of this prokaryotic cell is enclosed by a plasma membrane the plasma membrane that encloses the cytoplasm within the prokaryotic cell (recall that the single type of circular chromosome within prokaryotes is found within a region of the prokaryotic cell known as the nucleoid, which is a region and NOT an organelle) this plasma membrane enclosing the cytoplasm of the prokaryotic cell REGULATS The uptake of nutrients and the excretion of waste products so this plasma membrane of the prokaryotic cell is responsible for uptaking nutrients into the cell, and excreting any waste products that the cell has no use for right outside of the plasma membrane of a prokaryotic cell is a RIGID CELL WALL this rigid cell wall has the responsibility of protecting the prokaryotic cell from breakage the rigid cell wall located right outside of the plasma membrane of the prokaryotic cell is responsible for protecting the cell from breakage there are particular species of bacteria that have ANOTHER OUTER MEMBRANE this additional outer membrane is located right beyond the cell wall

experimental treatments that promote polyploidy

there are experimental treatments that can promote polyploidy there are experimental treatments that can promote polyploidy because polyploid and allopolyploid plants often exhibit desirable traits, the development of polyploids is of considerable interest amongst plant breeders the development of polyploids and allopolyploids is a point of interest for plant breeders, as polyploids and allopolyploids have been shown to have advantageous and desirable traits there have been experimental studies implemented that focused on the ability of environmental agents to promote polyploidy previously implemented environmental studies that concentrated on the ability of environmental agents to promote polyploidy began in the early 1990s, as scientists wanted to discover the ability of environmental agents to promote polyploidy, as polyploidy had been shown and shows to this day to produce advantageous and desirable traits scientists wanted to see if there were environmental agents that could increase the likelihood of polyploidy, which would cause an organism to have those desirable and advantageous traits since that time, there have been various environmental agents that have been shown to promote nondisjunction and therefore lead to polyploidy, where an organism has a multitude of sets of chromosomes, three or more sets of chromosomes, and therefore has advantageous and desirable traits these environmental agents that increase the likelihood of polyploidy include abrupt temperature changes during the initial stages of seedling growth, abrupt temperature changes during the initial stages of seedling growth can cause nondisjunction and the development of a polyploid organism with advantageous traits another environmental agent that can cause nondisjunction and result in a polyploid offspring with advantageous and desirable traits being produced is the treatment of plants with chemical agents that interfere with the formation of the spindle apparatus that assists in the separation of chromosomes the treatment of plants with chemical agents that interfere with the formation of the spindle apparatus can cause nondisjunction to occur and for a polyploid offspring to develop with advantageous and desirable traits the drug colchine is commonly used in order to promote polyploidy the drug colchicine is commonly used in order to promote polyploidy the drug colchicine is utilized in order to promote cellular division, and in doing so also promotes polyploidy once inside of the cell, colchicine binds to tubulin, which is a protein found within the spindle apparatus once inside of the cell, once the colchicine is inside of the cell, colchicine binds to the tubulin, which is a protein that composes the spindle apparatus, and thereby due to the binding of colchicine to tubulin, which is a protein composing the spindle apparatus, it interferes with the normal chromosome segregation that occurs during mitosis or meiosis due to colchicine once it is located inside the cell, binding to tubulin a protein that composes the spindle apparatus, it interferes with the normal segregation of chromosomes that occurs thanks to the proper functioning of spindle apparatus during anaphase of mitosis, anaphase I of meiosis, and anaphase ii of meiosis in 1936, Alfred Blakesless and Amos Avery applied colchicine to plant tissue, and at high doses of colchicine to the plant tissue, were able to cause COMPLETE MITOTIC NONDISJUNCTION, and produced polyploidy in plant cells colchicine can be applied to: seeds young embryos rapidly growing regions of a plant colchicine can be applied to seeds, young embryos, or rapidly growing regions of a plant and in high doses of colchicine that were applied to the pants, Alfred Blakeslee and Amos Avery were able to cause complete mitotic nondisjunction within these plants, producing polyploidy within the cells of these plants colchicine can be applied to seeds, young embryos, and rapidly growing regions of a plant this application of colchicine to seeds, young embryos, or rapidly growing regions of a plant that are consistently undergoing mitotis can cause aneuploidy which is an undesirable outcome however, the application of colchicine to seeds, young embryos, or rapidly developing and growing regions of a plant may cause polyploidy, may produce polyploidy plant cells though interfering with the spindle apparatus and causing complete mitotic nondisjunction these synthesized polyploid plant cells may grow faster than the surrounding diploid plants cells composing diploid plant tissue in a diploid plant, colchicine the application of colchicine may cause complete mitotic nondisjunction, where all of the chromosomes segregate into a single cell during mitosis, yielding tetraploid (4n) cells as these tetraploid cells continue to divide, these tetraploid cells containing 4 sets of chromosomes due to complete mitotic nondisjunction occurring within a diploid cell and resulting in all of the replicated chromosomes as well as the original chromosomes, the original two sets and the two copies of that two sets not being divided amongst two daughter cells but rather being placed in a single daughter cell, making that daughter cell a tetraploid cell, with 4 sets of chromosomes as these tetraploid cells continue to divide, they generate a portion of the plant that is often morphologically distinguishable from the remainder of the plant as these tetraploid cells created due to complete mitotic nondisjunction resulting from the application of colchicine, they generate a portion of the plant that is morphologically distinguishable from the rest of the plant, a region of the plant that is morphologically different and distinguishable from the rest of the plant an example of how tetraploid cells develop into regions that are morphologically distinct and different from the rest of the plant is how a tetraploid stem composed of tetraploid cells may have. larger diameter and produce larger leaves and flowers, making this region of the plant developed from tetraploid cells morphologically distinct and different from the rest of the plant individual plants can be propagated asexually individual plants be propagated asexually individual plants can be propagated asexually individual plants can be propagated asexually individual plants can be propagated asexually, and because individual plants can be propagated asexually from pieces of plant tissues (ie, cuttings of plant tissue), the polyploid portion of the plant can be removed, treated with the proper growth hormones that it requires, and be grown as a separate and individual plant, due to the ability of individual plants to propagate asexually with cuttings/pieces of plants alternatively, the tetraploid region of a plant may have flowers that produce seeds by self pollination alternatively, the tetraploid region of a plant may have flowers that produce seeds by self pollination for many plant species, a tetraploid flower produces diploid pollen and eggs, and these diploid pollen and eggs can combine in order to produce tetraploid offspring these diploid pollen and eggs can combine in order to produce tetraploid offspring these diploid pollen and eggs can combine in order to produce tetraploid offspring in this way, the use of colchicine provides a straightforward method of producing polyploid strains of plants, as the cutting can be taken and grown as individual plants due to the ability of individual plants to develop asexually with cuttings, or have flowers that are tetraploid and produce eggs and pollen that are diploid, and when combined, create a tetraploid offspring, propagating the line of tetraploid plants

genomic imprinting and the inheritance of certain human genetic diseases

there are human diseases (diseases found in humans): - Prader-Willi syndrome (PWS) - Angelman syndrome (AS) both of these human diseases are influenced by the process of genomic imprinting PWS- PRADER WILLI SYNDROME characteristics: - reduced motor function (less functionality in regards to body movement) - obesity - small hands and feet (reduced size of the hands and fit) AS- ANGELMAN SYNDROME characteristics: - thin (body type is thin) - hyperactive (an excess amount of energy) - the occurrence of unusual seizures - receptive symmetrical (occurring on both sides of the body) muscle movements (so mirroring muscle movements) - mental deficiencies both PWS AND AS both Prader Willi syndrome and Angelman syndrome involve a minor deletion within human chromosome 15 if the deletion in chromosome 15 is maternally inherited- then the offspring will have Angelman syndrome (if they inherited a chromosome 15 from their mother with a deletion in it) if the deletion in chromosome 15 is paternally inherited- then the offspring will have Prader Willi syndrome (if they inherited a chromosome 15 from their father with a deletion in it research has been done on the region of chromosome 15 that when deleted either maternally or paternally can cause either Angelman or Prader Willi syndrome respectively on this particular region of chromosome 15, there are closely linked (but still distinguishable and distinct) genes that are either maternally or paternally imprinted Angelman syndrome results from the lack of expression of a single gene known as UBE3A this single gene UBE3A whose lack of expression leads to Angelman syndrome, codes for a protein designated as E6-AP this protein E6-AP coded for by the UBE3A gene, has the function of transferring small ubuiquitin molecules to particular proteins in order to target and cause those particular proteins' degradation both copies of the E6-AP protein are very active in many of the tissues of the human body, their function of transferring small ubiquitin molecules to particular proteins in order to target and cause their degradation is an important function required in many of the body's tissues however, particularly in the brain, only the maternally inherited copy of the E6-AP protein is active and functions the paternal allele of the UBE3A gene coding for its own respective copy of the E6-AP protein is silenced and not transcriptionally active within the tissues of the brain, and therefore the E6-AP protein coded for by the paternally inherited allele of the UBE3A gene is not produced, and does not function within the tissues of the brain therefore, if the remaining E6-AP protein coded for by the maternally inherited allele is not there, due to a deletion of the maternally inherited allele, then the individual will develop Angelman syndrome, due to the fact that they will have no transcriptionally active copies of the UBE3A gene, neither maternally nor paternally inherited (as the paternal allele was already silenced, and then there was a deletion of the maternally inherited allele, resulting in no produced copies of the E6-AP protein in the tissues of the brain) researchers are unsure as to which genes in particular are responsible for Prader-Willi syndrome however within this region of chromosome 15 that researchers known influence the possibility of Prader Willi syndrome, there are five imprinted genes one gene candidate- SNRPN the gene product of the SNRPN gene is something that is part of A SMALL NUCLEAR RIBONUCLEOPROTEIN POLYPEPTIDE N the small nuclear ribonucleotprotein polypeptide N is a complex (which the gene product of the SNRPN gene is a part of) this complex controls RNA splicing, and is necessary for the synthesis of important proteins in the brain the maternally inherited allele of SNRPN (recall that the gene SNRPN Is coding for a small portion that is part of the complex- small nuclear ribonucleoprotein polypeptide N) is silenced the paternally inherited allele of the SNRPN is transcriptionally active, and expressed within the organism so only the paternally inherited allele of the SNRPN gene is transcriptionally active, and therefore only this allele codes for one functional, active copy of the small portion off the small nuclear ribonucleoprotein polypeptide N that will be responsible for controlling the process of RNA splicing and assisting in the synthesis of critical proteins within the brain (o one would presume if there is a deletion of the paternally inherited allele of the SNRPN gene, then the individual will have Prader-Willi syndrome)

natural and experimental ways to produce variations in chromosome number

there are natural and experimental ways to produce variation in chromosome number as we have seen, variations in chromosome number are fairly widespread and usually have a significant effect on the phenotypes of plants and animals variations in chromosome number are fairly widespread and they usually have a significant effect on the phenotypes of plants and animals variations in chromosome number are fairly widespread and they usually have a significant effect on the phenotypes of plants and animals variations in chromosome number are fairly widespread and they usually have a significant effect on the phenotypes of plants and animals for these reasons researchers have wanted to understand the cellular mechanisms that cause variations in chromosome number for these reasons researchers have wanted to understand the cellular mechanisms that cause variations in chromosome number researchers have wanted to understand the cellular mechanism that cause variations in chromosome number in some cases, an alteration, a change in chromosome number is the result of nondisjunction in some cases an alteration, a change in chromosome number is the result of nondisjunction in some cases, an alteration, a change in chromosome number is the result of nondisjunction the term NONDISJUNCTION what does nondisjunction refer to nondisjunction refers to an event in which the chromosomes do not segregate properly from one another nondisjunction refers to an event in which the chromosomes do not segregate properly from one another nondisjunction refers to an event in which the chromosomes do not segregate properly from one another what is nondisjunction caused by, why do chromosomes not segregate properly from one another chromosomes do not segregate properly from one another, and this may be caused by an improper separation of homologous pairs in a bivalent in meiosis chromosomes not separating properly from one another, a phenomenon known and recognized as nondisjunction, could occur because of two reasons chromosomes not separating properly from one another may be caused by: an improper separation of homologous pairs in a bivalent in meiosis or a failure of the centromeres of these pairs of sister chromatids to disconnect during meiosis MEIOTIC NONDISJUNCTION what is meiotic nondisjunction meiotic nondisjunction, the chromosomes not separating properly in meiosis, can produce haploid daughter cells that have too many or too few chromosomes meiotic nondisjunction, where the chromosomes are not separating properly during meiosis, can produce haploid daughter cells that have too few or too many chromosomes due to the improper segregation of chromosomes that occurred during meiosis if such a cell, a haploid cell with too few or too many chromosomes due to meiotic nondisjunction fuses with a genotypical normal gamete with the appropriate amount of genetic material during fertilization, the resulting offspring from this union bw a gamete with a. chromosome number abnormality and a normal gamete with the approbate amount of genetic material will produce offspring with an abnormal chromosome number found within all of its cells an abnormal nondisjunction event also may occur after fertilization in the somatic cells of the body nondisjunction may also occur after fertilization in the somatic cells of the body nondisjunction may also occur after fertilization in the somatic cells of the body nondisjunction may also occur after fertilization in the somatic cells of the body rather than in the gametes that participate in fertilization THIS SECOND MECHANISM where nondisjunction occurs after fertilization in the somatic cells of the body rather than during meiosis when gametes are being formed mitotic nondisjunction when mitotic nondisjunction occurs during embryonic stages of development, it may lead to a patch of tissue in the organism that has an abnormal chromosome number, rather than the entire organism and all of its somatic cells having an abnormal chromosome number, which is what occurs when meiotic nondisjunction occurs due to mitotic nondisjunction, this process of mitotic nondisjunction occurs during embryonic stages of development when mitotic nondisjunction occurs during embryonic stages of development, it may lead to a patch of tissue within the developed organism where there is an abnormal chromosome number, rather than all of the somatic cells of this organism having an abnormal chromosome number there is third common way in which the chromosome of an organism can vary THERE IS A THIRD COMMON WAY IN WHICH THE CHROMOSOME OF AN ORGANISM CAN VARY there is a third common way in which the chromosome number of an organism can vary there is a third common way in which the chromosome number of an organism can indeed vary this third common way in which the chromosome number of an organism can vary is by INTERSPECIES CROSSES an alloploid organism contains sets of chromosomes from two or more different species an alloploid organism contains sets of chromosomes from two or more different specie this term alloploid, referring to an organism that contains different sets of chromosomes from two or more different species, refers to the occurrence of chromosome sets (ploidy) from the genomes of different (allo) species IN THE PAST FEW DECADES researchers have devised several methods for manipulating the chromosome number in experimentally and agriculturally important species

symbiotic infective particles

there are other unusual endosymbiotic relationships that have been discovered and established within eukaryotic organisms there are several examples of endosymbiotic relationships in which there are infectious particles that establish a symbiotic relationship with their host there are also cases in which these infectious particles that partake in a symbiotic relationship with their host are bacteria that exist and reside within the cytoplasm of eukaryotic cells so these infectious particles that participate in a symbiotic relationship with their host are shown through conducted and implemented research to be bacteria that find their way into the cytoplasm of eukaryotic cells and reside symbiotic infectious particles are fairly uncommon, but they are related to extranuclear inheritance Tracy Sonneborn studied a phenomenon designated as THE KILLER TRAIT this killer trait was found in the protozoan Paramecium Aurelia Tracy Sonneborn studied this kill trait within the protozoan Paramecium Aurelia in the 1940s killer paramecia are organisms that secrete a substance designated as paramecin so killer paramecia secrete paramecin paramecin (which is secreted by killer paramecia) kills some but not all strains of Paramecium Aurelia Tracy Sonneborn, who was researching the killer trait found within the protozoan Paramecium Aurelia, discovered that killer strains of paramecia contain particles within their cytoplasm these particles within killer paramecia's cytoplasm are designated as kappa particles a kappa particle is 0.4 micrometers long, and a kappa particle also contains its own set/entity of DNA there are genes within the kappa particles within the cytoplasm of the cells of the killer strain of paramecium, and these genes code for the paramecin toxin that the killer strain of paramecia secrete the genes within the kappa particle also provide the killer paramecia itself with protection from and resistance to the paramecin toxin it secretes (that is known to kill a multitude of strains of paramecia) when Sobornne mixed nonkiller paramecia with killer paramecia, all of the nonkiller paramecia were killed by the paramecin toxin secreted by the killer paramecia however, when the nonkiller paramecia were mixed with a cell extract taken from killer paramecia, the kappa particles found within the extract were taken up into the nonkiller paramecia, turning the nonkiller paramecia into killer paramecia, and therefore not causing their death therefore sobornne determined that the extranuclear particle, the kappa particle, that codes for the toxin paramecin that kills a multitude of strains of paramecia is infectious to other paramecia another example of an infectious particle: one found within fruit flies Philippe l'héritier was able to identify particular strains of Drosophila melanogaster, these strains of Drosophila melanogaster are quite sensitive to CO2, and can be killed by the presence of CO2 when this researcher conducted reciprocal crosses bw Drosophila melanogaster that were sensitive to CO2 and those that were not, he understood that the trait of CO2 sensitivity is inherited in a pattern that does not align with any established Mendelian patterns he also discovered that if you take cell extracts from a CO2 sensitive fly, and place these extracts upon normal flies without sensitive to CO2, these normal flies will become infected with this condition and become sensitive to CO2 there is another example of an infectious particle discovered within fruit flies: this infectious particle has a relationship with a trait called sex rate sex ratio is a trait where flies affected by the sex ratio trait produce progenies that are majority female there were two researchers that researched this trait, Chana Malogolowkin and Donald Poulson these two above researchers discovered a particular strain of Drosophila willistoni within this strain of Drosophila willistoni, the majority of the offspring of the female flies were daughters, while any offspring that were male died the sex ratio trait that causes flies to produce progeny that are excess and majority female is passed from mother to offspring the males that survive are not able to transmit the sex ratio trait to its offspring, only mothers can transmit this trait to offspring (though males are still affected if they have this trait, they simply cannot pass it on to their offspring, as that is done from the mother to the offspring due to maternal inheritance) there is an agent within the cytoplasm of female flies this agent within the cytoplasm of female flies is responsible for the expression of the sex ratio trait that causes organisms to produce progeny that are majority or excess female the agent within the cytoplasm is designated as Spiroplasma poulsonii the presence of this agent within the cytoplasm is usually lethal to male offspring, causingtoheir deaths this agent Spiroplasma poulsonii can be extracted from the tissues of adult females with this agent in their cytoplasm, and can infect normal females without this agent and trait

phenotypic effects involving sex chromosomal abnormalities

there are phenotypic effects, phenotypic consequences involving sex chromosome abnormalities, abnormalities in sex chromosomes what are these phenotypic effects, these phenotypic consequences that result from abnormalities in regards to sex chromosome there is the condition of trisomy 13, which is where an afflicted individual with trisomy 13 contains 3 copies of chromosome 13 rather than the requisite and typical two copies of chromosome 13 that it should have, resulting in excess gene product of the genes on chromosome 13 being created, potentially 150% gene product due to the presence of 3 chromosome 13's and therefore 3 copies of every gene on chromosome 13 rather than just 2 the frequency of trisomy 13 is 1/15,000 the frequency of trisomy 13 the frequency of the condition of trisomy 13 is 1/15,000 there is a syndrome that can develop from trisomy 13, known as PATAU SYNDROME patau syndrome is the disease that is the phenotypic consequence of trisomy 13, it is a syndrome that results from an individual being afflicted with trisomy 13 also recall that the most common trisomies occur in chromosome 13, 18, and 21 if there are trisomies in any other autosomal chromosomes, they are presumed to be lethal trisomies, not resulting in a viable embryo that will develop if there are monosomes in any of the autosomal chromosomes, these monosomes are also considered lethal and will result in nonviable embryos, potentially spontaneous abortions due to the embryo not being able to develop properly if there is a trisomy 1, this condition has never been found within spontaneously aborted embryos and fetuses, it is considered that this condition has never been spotted in spontaneously aborted embryos and fetuses as other trisomies have been, because trisomy 1 involves such a necessary and large chromosomes containing an enormous number of genes, that this chromosomal number aberration in regards to their being 3 copies of chromosome 1 will prevent the embryo from ever being able to implant itself within the uterus and develop in the first place so patau syndrome results from trisomy 13, an individual having 3 copies of chromosome 13 in their genome rather than the requisite number of 2 copies of chromosome 13 the characteristics of PATAU SYNDROME include: mental and physical deficiencies wide variety of defects in organs large triangular nose early death the characteristics of PATAU syndrome include: mental and physical deficiency, a wide variety of defects within the organs, a large triangular nose, and early death TRISOMY 18 is another chromosomal number aberration, a type of aneuploidy where the individual afflicted with trisomy 18 has three copies of chromosome 18 an individual afflicted with trisomy 18- the frequency of this is 1/6000, so slightly more common than the frequency of trisomy 13, whose frequency is 1/15000 the individual afflicted with trisomy 18, will usually present with Edward syndrome an individual afflicted with trisomy 18 will usually present with Edward syndrome what are the characteristics of Edward syndrome, that arises due to trisomy 18, and individual having 3 copies of chromosome 18 within their genome the characteristics of Edward syndrome are: mental and physical deficiencies facial abnormalities extreme muscle tone early death the characteristics of Edward syndrome that arises from trisomy 18 are mental and physical deficiencies, facial abnormalities, extreme muscle tone, and early death TRISOMY 21 is a condition where an individual afflicted with trisomy 21 has aneuploidy, a specific type of chromosome number aberration where the copies of a particular type of chromosome within a set are affect, the number of copies of a particular type of chromosome within a set is altered, the number of copies of a particular type of chromosome is change, resulting in an alteration of the total chromosome number and the organism no longer being considered euploid, because its total chromosome number will no longer be a multiple of a typical single chromosome set found within a typical organism within its species trisomy 21 has a frequency of 1/800, so it is the most frequent out of the generally most frequent trisomies, the only trisomies found that result in developed embryos and fetuses and born fetuses, as the frequency of patau syndrome is 1/15,000 and the frequency of Edward syndrome is 1/6000 Down syndrome arises from trisomy 21 what are the characteristics of down syndrome the characteristics of down syndrome include mental deficiencies abnormal pattern of palm creases slanted eyes flattened face short stature the characteristics of Down syndrome include mental deficiencies, an abnormal pattern of palm creases, slanted eyes, flattened face, and short stature sex chromosomal abnormalities- ABNORMALITiES IN SEX CHROMOSOMES and the RESULTING CONDITIONS FROM THESE SEX CHROMOSOMAL ABNORMALITIES one of these conditions is where an organism has the sex chromosome, the allosomal combination of XXY the frequency of this particular allosomal combination, XXY, the frequency of this sex chromosome conglomeration of XXY in an individual is 1/1000 (males in particular, as this is a condition that occurs in males) the syndrome that arises from this condition of XXY is Klinefelter syndrome, which is characterized by sexual immaturity (no sperm production will occur in an individual with Klinefelter syndrome) and breast swelling another condition is where the organism has the allosomal combination, the sex chromosome compilation and conglomeration XYY this chromosome conglomeration of XYY has a frequency of 1/1000 (males) the syndrome that develops from this condition, from this sex chromosome combination and conglomeration of XYY is Jacobs syndrome the characteristics of Jacobs syndrome, a syndrome that results from the chromosomal combination and conglomeration of XYY, Jacobs syndrome is a syndrome that results from the sex chromosomal and conglomeration XYY the characteristics of jacobs syndrome, a syndrome that results from the sex chromosomal compilation XYY are tall and thin the characteristics of jacobs syndrome, a syndrome resulting from the sex chromosomal compilation and conglomeration XXY are tall and thin, tall height, thin body another condition having to do with sex chromosome abnormality is where an individual has the allosomal combination/compilation of XXX the frequency of this condition, of the allosomal combination the sex chromosome compilation/combination of XXX is 1/1500 (females) the syndrome that results from this particular chromosomal combination, this particular chromosomal conglomeration is triple x syndrome the characteristics of triple x syndrome include: tall and thin menstrual irregularity the characteristics of triple x syndrome include tall and thin, tall height, thin body, and menstrual irregularity, and triple x syndrome results from trisomy x, an individual afflicted with trisomy x having three copies of the x chromosome rather than the requisite 2 it should have as a female the frequency of this condition is 1/1,500 (females) another condition having to do with sex chromosome abnormality is a condition where the organism has the allosomal combination/compilation of X0, where the organism has the sex chromosome compilation of X0, one x chromosome and no other chromosome to join it in the sex chromosome pair the frequency of this condition is 1/5000 (females) the syndrome that results from this condition of the allosomal chromosome combination X0 is Turner syndrome the characteristics of turner syndrome include: short stature webbed neck sexually underdeveloped the characteristics of Turner syndrome include: short stature, webbed neck, and sexual underdevelopment recall that Turner syndrome comes about due to an individual having the allosome combination, the sex chromosome combination X0, and the frequency of this syndrome, of the condition X0 where the allosomal combination the sex chromosome combination of an individual is X0 is 1/5000 (female) the phenotypic effects noted above, the phenotypic effects resulting from allosomal, sex chromosome abnormalities may be due to the expression of particular x linked genes prior to embryonic x inactivation, or to the expression of genes on the X chromosome that is inactivated, some genes on this X chromosome still managing to be transcribed despite the X chromosome they are on having being turned into a barr body and therefore becoming transcriptionally inactive because presumably, due to the occurrence of x inactivation, it should not be possible for these syndromes to develop out of the presence of more than a single X chromosome or more than 2 X chromosomes due to the process of x inactivation that should result in the limitation of expression of x linked genes to one X chromosome in every somatic cell of every organism, the gene expression of x linked genes being linked always to a single X chromosome and only that single x chromosome due to the phenomenon of x inactivation however, it is considered that these conditions and syndromes related to sex chromosome abnormality may come about, because there may be expression of X linked genes on a chromosome marked for compaction prior to embryonic x inactivation occurring to that chromosome, resulting in x linked genes that should not have been expressed being expressed, due to be transcribed and expressed prior to the implementation of the process of x inactivation of the chromosome these genes were on another possibility is some genes, x linked genes located on an inactivated x chromosome still being transcribed even after x inactivation of the chromosome they are located on being inactivated, also resulting in the expression of x linked genes, copies of x linked genes that should not be expressed being expressed despite the X chromosome that they are on being inactivated, there is still technically a possibility of transcription of x linked genes that can indeed occur in chapter 5, it was described and explained that pseudoautosomal genes, genes that operate and are inherited in the same manner as autosomal genes, found perhaps within the sex chromosomes, but on both sex chromosomes in particular, both x and y, as well as other genes on the inactivated chromosome are expressed within humans having one or three copies of these sex chromosomes, therefore due to the genes that function and are inherited as autosomal genes, as well as the genes on inactivated chromosomes that are still somehow transcribed, can cause these types of combinations of sex chromosomes to still have phenotypic consequences n spite of the presence and the potential/expected implementation of x chromosome inactivation

X and Y chromosome homology

there are short regions of homology amongst X and Y chromosomes where the chromosomes carry the same genes that is how they are considered homologous along those particular lengths human sex chromosomes (X and Y) have 3 main homologous regions, as well as several other homologous regions these homologous regions are evolutionarily related and promote the necessary pairing of X and Y chromosomes (their homology contributes to this pairing) that occurs during meiosis I of spermatogenesis (the formation of sperm, the X and Y chromosomes need to be paired for crossover possibilities prior to separation, and be able to identify one another as pair- though not a fully homologous one so they can properly separate during anaphase II of meiosis II into proper gametes) very few genes located in these homologous regions bw X and Y chromosomes pseudoautosomal gene- Mic2- is found on both X and Y chromosomes the Mic2 genes codes for a cell surface antigen researcher estimates of gene number: X chromosome- bw 900 and 1200 genes Y chromosome- bw 70 and 300 genes

variations in euploidy within particular tissues of an animal

there are variations in euploidy that can occur in certain particular tissues within an animal there are variations in euploidy that can occur in certain particular tissues within an animal there are variations in euploidy that can occur in certain particular tissues within an animal there are variations in euploidy that can occur in certain particular tissues within an animal there are variations in euploidy that can occur in certain particular tissues within an animal thus far we have considered variations in chromosome number that occur at fertilization, when two gametes combine with one another in order to form a zygote so far we have considered variations in chromosome number that occur at fertilization, when the two gametes combine with one another to form a zygote, and an abnormality in chromosome number appears, so that all of the subsequently formed somatic cells of an individual thus contain this chromosomal variation, this abnormality in chromosome number found in the original zygote in many animals, certain tissues of the body display normal variations in the number of sets of chromosomes certain tissues of the body display normal variations in the number of sets of chromosomes certain tissues of the body display normal variations in the number of sets of chromosomes within the cells of these tissues diploid animals sometimes do produce tissues that are polyploid diploid animals sometimes do produce tissues that are polyploid diploid animals sometimes do produce tissues that are polyploid an example of how diploid animals sometimes do produce tissues that are polyploid an example of how diploid animals sometimes do produce tissues that are polyploid an example of how diploid animals sometimes do produce tissues that are polyploid is that the cells of the human liver can vary to a great degree in their ploidy the cells of the human liver can vary to a great degree in their ploidy the cells of the human liver can vary to a great degree in their ploidy liver cells contain nuclei that can be: triploid tetraploid and even octaploid (8n) the occurrence of polyploid tissues or cells in organisms that are otherwise diploid is known as endopolyploidy the occurrence of polyploid tissues or cells in organisms that are otherwise diploid is known as endopolyploidy the occurrence of polyploid tissues or cells in organisms that are otherwise diploid is known as endopolyploidy the occurrence of polyploid tissues or cells in organisms that are otherwise diploid is known as endopolyploidy the occurrence of polyploid tissues or cells in organisms that are otherwise diploid is known as endopolyploidy liver cells contain nuclei that can be triploid, tetraploid, and even octaploid (8n) what is the biological significance of endopolyploidy, the presence of polyploid tissues or cells in organisms that are otherwise diploid what is the biological significance of endopolyploidy one possibility is that the increase in chromosome number in certain cells may enhance their ability to produce specific gene products that are required in great abundance one possibility for the biological significance of endopolploidy is that the increase in chromosome number, the polyploidy in particular cells or tissues may enhance the ability of these cells or tissues to produce particular gene products that are required in greater amounts in greater abundance, these gene products need to be produced in excess, and the implementation and presence of polyploidy occurring, increasing the number of chromosomes, and therefore increasing the number of copies of genes producing those gene products may assist in that amount of gene product being achieved an unusual example of natural variation in the ploidy of somatic cells there is an unusual example of natural variation in the ploidy of somatic cells occurring there is an unusual example of natural variation in the ploidy of somatic cells occurring there is an unusual example of natural variation in the ploidy of somatic cells there is an unusual example of natural variation in the ploidy of somatic cells within drosophila and some other insects within certain tissues, such as the salivary glands, the chromosomes undergo repeated rounds chromosome replication within certain tissues, such as the salivary glands of drosophila melanogaster and other insects, the chromosomes within these particular tissues, such as the salivary glands undergo repeated rounds of chromosome replication without cellular division within particular tissues of drosophila melanogaster and other insects, such as the salivary glands, chromosomes undergo repeated rounds of chromosome replication without cellular division occurring an example of this is how within the salivary gland cells of drosophila, the cells composing the salivary glands of drosophila, the pairs of chromosomes double approximately nine times 2^9= 512 chromosomes total so within these cells, the pairs of chromosomes double about 9 times, leading to 512 chromosomes being present in each of the cells composing the salivary glands of the drosophila melanogaster organisms there is a figure that introduces and illustrates how repeated rounds of chromosomal replication produce a bundle of chromosomes that lie together in a parallel fashion there is a figure that introduces how repeated rounds of chromosomal replication produce a bundle of chromosomes that lie together in a parallel fashion next ot one another this bundle is designated as a polytene chromosome, a bundle of chromosomes that lie next to one another in a parallel fashion is designated as a polytene chromosome this structure, a polytene chromosome where there is a bundle of chromosomes lying next to one another in a parallel fashion was first observed by E.G. Balbiani in 1881 later in the 1930s, Theophilus Painter and his colleagues recognized that the size and the morphology, the physical appearance of polytene chromosomes provide geneticists with unique opportunities to study chromosome structure and gene organization Theophilus Painter and his colleagues recognized that the size and the morphology, the physical appearance of polytene chromosomes both (both the size and morphology, the physical appearance of these polytene chromosomes) provide geneticists with unique opportunities to study chromosome structure and gene organization the size and morphology of polytene chromosomes provide geneticists the opportunity, unique opportunities to study chromosome structure and gene organization recall that a polytene chromosome is a bundle of chromosomes that are lying next to one another in a parallel fashion, and these chromosomes result from repeated rounds of chromosome replication that occur within cells (recall that within the cells composing the salivary glands of drosophila melanogaster, these cells undergo repeated rounds of chromosome replication without cellular divisions, and this results in the presence of polytene chromosomes, bundles of chromosomes that are lying next to one another in a parallel fashion) we can look at a micrograph of a polytene chromosome we can look at the micrograph of a polytene chromosome the structure of polytene chromosomes is different from other forms of endopolyploidy where there are polyploid cells or tissues in an organism that is diploid the structure of polytene chromosomes is different from other forms of endopolyploidy bc the replicated chromosomes remain attached to one another the structure of polytene chromosomes is different from other forms of endopolyploidy bc the replicated chromosomes remain attached to one another in the structure of bundles, where the chromosomes are lying next to one another in a parallel fashion the replicated chromosomes in polytene chromosomes remain attached to one another prior to the formation of polytene chromosomes, drosophila cells contain 8 chromosomes, 2 sets of 4 chromosomes each totaling out to 8 chromosomes in the salivary gland cells of drosophila however, the story is quite different within the salivary gland cells, the homologous chromosomes synapse with one another and replicate in order to form a polytene structure within the salivary gland cells of drosophila, the homologous chromosomes synapse with one another and replicate in order to form a polytene structure the homologous chromosomes synapse with one another and replicate in order to form a polytene chromosome structure during this process of the homolog chromosomes synapsing with one another and replicating in order to form a polytene chromosome, the four types of chromosomes that are within the somatic cell of the salivary gland, there are 4 different types of chromosomes, all in pairs, totaling out to 8 chromosomes, the four types of chromosomes aggregate in order to form a single structure with several polytene arms the four types of chromosomes aggregate with one another in order to form a single structure with several polytene arms the four types of chromosomes, 2 to a particular type of chromosome aggregate with one another in order to form a single structure with several polytene arms the central point where all 4 types of chromosomes found in pairs aggregate and conglomerate with one another is known as the chromosome center the central point where the 4 types of chromosomes found in pairs aggregate and conglomerate with one another is known as the chromocenter each of the four types of chromosome is attached to the chromocenter near its centromere there is a structure formed where the four types of chromosomes aggregate and conglomerate with one another in order to form a structure with several polytene arms the center where all these 4 types of chromosomes found in pairs aggregate and conglomerate is known as the chromocenter, and each type of chromosome is attached to the chromocenternear its centromer the x and y and chromosome 4 are telocentric, meaning the centromere of these chromosomes is located at the end of these chromosomes the chromosomes 2 and 3 are metacentric, where the centromere is located within the center of these chromosoems so the x and Y chromosomes and chromosome 4 are telocentric, while chromosome 2 and 3 are metacentric, and all these chromosomes are attached to the chromocenter near their respective centimes therefore, chromosomes 2 and 3 both have 2 arms radiating out from the chromocenter, due to them being metacentric, having their centromeres at the center of their structures, attaching near the chromocenter and the x and y chromosomes and chromosome 4 which are all telocentric and have their centromeres located at the end of their structures are also attached to the chromocenter near their centromeres, thus having a single arm projecting from the chromocenter

lethal allele ratios

there can be scenarios in which lethal allele ratios are markedly different from Mendelian ratios an example of the marked difference in ratio is shown by the Manx cat, that originated on the iSle of Man amongst this cat breed, Manx, a dominant mutation impacting the spine is prevalent this mutation when present and expressed, causes the tail length to shorten the tail length amongst Manx can therefore be normal, short, or nonexistent when 2 Manx cats (which can apparently only be heterozygous, bc a homozygous dominant allelic combination results in early embryonic death, and a homozygous recessive allelic combination means the cat can no longer be identified as Manx), the ratio of offspring is 1 normal cat to 2 Manx 1/4 of the offspring created by 2 Manx cats die early during embryonic development/formation the Manx phenotype- dominant the lethal phenotype- occurs when the individual is homozygous dominant for a short-nonexistent tail

bacterial species and FtsZ

there has been recent research conducted and evidence collected that indicates that bacterial species (any bacterial species, generally) produces a protein designated as FtsZ the protein FtsZ that bacterial species produce are IMPORTANT IN CELL DIVISION the protein FtsZ that research and evidence collected prove bacterial species produce is IMPORTANT IN CELLULAR DIVISION, IMPORTANT IN THE CELLULAR DIVISION THAT OCCURS WITH BACTERIAL CELLS the conjecture surrounding the FtsZ protein due to the research that has been conducted and the evidence that has been collected, indicates the the FtsZ protein functions in the way that it assembles into a ring the FtsZ protein apparently assembles into a ring right at the site within the bacterial cell where the septum will eventually form, dividing the original bacterial cell into two identical daughter cells the FtsZ protein is thought to be the first protein to arrive at this site of the future septum, the first protein to move to the division site, where the original bacterial cell will divide into two identical daughter cell once it (as the first protein) moves to the site of division within the bacterial cell, it will recruit other proteins that are responsible for producing a NEW CELL WALL bw the daughter cells so that the original cell will both divide into two genetically identical daughter cells, and these genetically identical daughter cells will be able to exist as separate, individual entities, independent bacterial daughter cells apparently the protein FtsZ is EVOLUTIONARILY RELATED TO TUBULIN to recall tubulin's function the function of the protein tubulin (to which FtsZ is evolutionarily related) is to be a component of microtubules tubulin is the main component composing the structures of microtubules within cells MICROTUBULES play an integral, critical role in separating chromosomes, separating chromosomal genetic material into two identical daughter cells during the anaphase stage of mitosis, microtubules play an integral role in attaching themselves to the kinetochores of the chromosomes (these microtubules that function this way are designated as kinetochore microtubules) and during anaphase, pulling back towards the centromeres they originally stem from, and taking equal numbers of chromosomes with them that will belong to 2 genetically identical daughter cells FtsZ and tubulin are both responsible for either forming and/or being components of structures that assist cells in organization of genetic material during cellular division and also play key roles in the actual process of division that occurs within cells the FtsZ protein contributes to the creation of the septum by recruiting proteins to produce a cell wall bw the proliferating daughter cells of an original bacterial cell tubulin composes microtubules which are responsible for pulling apart chromosomes and bringing equal amounts of genetic material to two daughter cells proliferating from an original eukaryotic cell during mitosis why is binary fission considered an ASEXUAL FORM OF REPRODUCTION? binary fission is considered an asexual form of reproduction, bc this form of reproduction, where a new organism/individual entity is formed not by the combination of genetic material from two gametes, but rather through the simple division of the genetic material from a single original cell within humans, the sperm cell and the egg cell, both haploid gametes, combine with one another in order to form a zygote which will then develop through mitosis and cell proliferation into a full blown organism however, within bacterial cells, the asexual reproduction process of binary fission occurs, where fully developed (and fairly simplistic) organisms develop from a single cell ON OCCASION< it is possible for bacterial cells to exchange small amounts of genetic material with one another (this process of exchange particular types of genetic material with one another, a somewhat equivalent of the process of crossing over that occurs during meiosis and the formation of gametes, resulting in variation within offspring and populations, will be delved into in Ch. 7)

the marking process of genomic imprinting

there is a marking process that researchers have found within the overall phenomenon of genomic imprinting during the processes of spermatogenesis (sperm production within male organisms) and oogenesis (egg production within female organisms) there is a particular gene, part of a chromosome, the entirety of a chromosome, or an entire set of chromosomes that is marked differently during these processes of gamete formation after the process of fertilization occurs (the process by which the egg and sperm join and form a zygote), the differential marking and imprinting that occurred in the individual haploid gametes that joined to form this zygote affects the gene expression and the phenotypic expression within this organism the molecular level explanation for the phenomenon of genomic imprinting: what occurs at the molecular level in order to cause genomic imprinting, taking the process one step underneath the cellular level DNA methylation is heavily involved in genomic imprinting

triploid

there is a rare alteration in euploidy that is possible on rare occasions, there can be abnormal fruit fly produced on rare occasions, an abnormal fruit fly can be produced this abnormal fruit fly can be produced, where this organism, an abnormal fruit fly, has 12 chromosomes total within its genome, containing 3 sets of 4 chromosomes each, therefore this organism contains an extra set of 4 chromosomes that the drosophila melanogaster organism does not require and usually does not have there are 3 sets of 4 chromosomes each within the genome of this organism, and therefore this organism is known as triploid rather than diploid, referring to the number of sets of chromosomes that this organism has a diploid organism would have two sets of chromosomes a triploid organism has three sets of chromosomes, and in this case, three sets of chromosomes each containing 4 chromosomes totaling out to 12 this fly is also still considered euploid why is this fly still considered euploid this is because the total number of chromosomes within the genome of this fly is still a multiple of a set of chromosomes within this species, it is a set of 4 chromosomes multiplied by 3 to total out to 12 chromosomes, the total number of chromosomes is a multiple of a single set of chromosomes, 4x3=12 it is considered euploid because it has exactly three sets of chromosomes ORGANISMS WITH THREE OR MORE SETS OF CHROMOSOMES ARE ALSO DESIGNATED AS POLYPLOID organisms with three or more sets of chromosomes are designated as polyploid, indicating that these organisms have more than simply two sets of chromosomes within them, they have a multitude of chromosomal sets making up their genome, 3 or more of these chromosomal sets geneticists also utilize the letter n in order to represent a single set of chromosomes the letter n is used to designate a single set of chromosomes a diploid organism will be given the designation 2n, indicating that this organism has 2 sets of chromosomes, as n stands for a single individual set of chromosomes a triploid organism will be designated as 3n, designating that it has 3 sets of chromosomes a tetraploid organism will have four sets of chromosomes and therefore be designated as 4n, indicating that a tetraploid organism has four sets of chromosomes

environmental effects and Drosophila melanogaster

there is an experiment shown in the book where fertilized eggs from a population of genetically identical Drosophila Melanogaster (so the exact same, identical Drosophila melanogaster, all having the same allelic combinations and thus presenting with identical phenotypic expression) were allowed to develop into adult flies at varying environmental temps their is a relationship bw the temperature these eggs are allowed to develop and the facet number in the eyes of the mature adult flies, less facet number in the eyes the higher the temperature those Drosophila Melanogaster eggs are allowed to develop (and bc the experiment is controlled, with all of the eggs being genetically identical, meaning that the facet number in the eyes of adults can not be attributed to anything other than the manipulated independent variable-temperature validates this experiment)

the existence of mitochondria and chloroplasts

there is an underlying reason for the distinct genomes of mitochondria and chloroplasts, the fact that there are separate entities of DNA within the nucleus, mitochondria, and chloroplasts the reason is their endosymbiotic relationship and their evolutionary origin encompassing that what is a symbiotic relationship? a symbiotic relationship is a relationship that occurs when there are two species that are living in close proximity to one another the SYMBIONT is the smaller of the two species living in close proximity the HOST is the larger of the two species living in close proximity what is endosymbiosis? endosymbiosis is a description of a symbiotic relationship where the symbiont resides insides of the host (so the proximity of the two species is that the symbiont, the smaller of the two species, resides inside of the host, the larger of the two species) there was a notion proposed by Andreas Schimper in 1883 that chloroplasts were descended from an endosymbiotic relationship that occurred bw CYANOBACTERIA AND EUKARYOTIC CELLS this proposed notion is designated as the endosymbiosis theory the endosymbiosis theory suggests that the ancient origin of chloroplasts was initiated due to this event: a cyanobacterium started to reside within a primordial eukaryotic cell, that is the origin of the chloroplast we see today within cells, an endosymbiotic relationship bw a cyanobacterium, the symbiotic, and the primordial eukaryotic cell, the host as evolution proceed, the characteristics of this intracellular bacterial cell (a cyanobacterium residing within a primordial eukaryotic cell) eventually altered to those matching the characteristics of the modern chloroplasts there was also a notion proposed of an endosymbiotic origin of mitochondria by Ivan Wallin in 1922 despite these proposed notions and hypothesis of endosymbiotic origin of chloroplasts and mitochondria, the notion and phenomenon of endosymbiosis was ignored then researchers in the 1950s discovered the presence of genetic material within chloroplasts and mitochondria, understanding that these organelles both contain their own distinct genetic material Lynn Margulis published a book called Origin of Eukaryotic Cells, and whatever she proposed within this book cause a debate on the possibility of endosymbiotic origin of organelles particular molecular genetic techniques allowed researchers to conduct various analyses on the genes of: -chloroplasts -mitochondria -bacteria -eukaryotic nuclear genomes the molecular genetic techniques that these researchers implemented on the genes of chloroplasts, mitochondria, bacteria, and eukaryotic nuclear genomes in the 1970s and 1980s led to the discovery that the genes found within chloroplasts and mitochondria are quite similar to the genes found in bacteria however, the genes found within chloroplasts and mitochondria are not very similar to the genes found within the nucleus of eukaryotic cells this discovery led to the acceptance of the endosymbiotic origin of mitochondria and chloroplasts the endosymbiotic theory proposes the notion that the relationship bw the cyanobacteria and the primordial eukaryotic cell helped the new eukaryotic cell exhibit useful and beneficial cellular characteristics how was the endosymbiotic relationship a cause for useful cellular characteristics? chloroplasts are derived from cyanobacteria (the symbiote) cyanobacteria are a bacterial species that has the capability of photosynthesis the ability of cyanobacteria as a bacterial species to conduct photosynthesis enables algal and plant cells to use energy they garner from sunlight mitochondria are considered to possibly have been derived from a different type of bacteria this different type of bacteria that mitochondria are considered to be derived from/a descendant of is designated as GRAM-NEGATIVE SULFUR PURPLE BACTERIA the endosymbiotic relationship bw the gram negative sulfur purple bacteria that the mitochondria descended form and the primordial eukaryotic cell allowed the newly formed eukaryotic cell to produce greater amount of energy in the form of ATP scientists are unsure of how the endosymbiotic relationship would assist the cyanobacteria or the purple bacteria specifically, rather than the resulting eukaryotic cell there is a theory that the cytosol of the eukaryotic cell resulting from the endosymbiosis bw the cyanobacteria/purple bacteria and the primordial eukaryotic cell provided a more stable environment to the mitochondria/chloroplast ancestors as well as an adequate amount of nutrients during the process of evolution of eukaryotic species, the majority of genes that were contained within the genome of the primordial cyanobacteria and the purple bacteria (each functioning as the symbiote of an endosymbiotic relationship) were lost, or transferred from these primordial organelles to the nucleus researchers understand that particular genes were transferred over the process of evolution from the organelles to the nucleus due to the fact that there are some sequences of particular genes within the nucleus, and the analyses of these sequences of genes within the nucleus reveal that these particular sequences of genes originate from an organelle (and specifically, either the organelle mitochondria or chloroplast) these sequences of genes found within the nucleus that originate from an organelle have been found to be far more similar to DNA sequences composing bacterial genes as opposed to DNA sequences found in these sequences of genes within the nucleus's eukaryotic counterpart the reason that researchers understand that these DNA sequences originate from organelles rather than the nucleus is their similarities to bacterial genes over their eukaryotic counterparts researchers understand that these gene sequences were removed from the mitochondrial and chloroplast chromosomes (the gene sequences contained within the mitochondrial and chloroplast chromosomes) and placed within the nuclear chromosomes throughout the process of evolution the reason that cyanobacteria and purple bacteria today are not identical to their counterparts of chloroplasts and mitochondria is due to these genetic changes where gene sequences were lost by chloroplasts and mitochondria through evolution and placed within the nucleus instead researchers have concluded that the majority of gene transfer (gene sequences within mitochondria and chloroplast chromosomes being shifted to nuclear chromosomes) occurred during the early portion of evolution within animals, the functional transfer of genes in mitochondrial chromosomes to nuclear chromosomes has stopped however, within plants, functional gene transfer of genes in mitochondrial and chloroplast chromosomes continues at a very slow rate there is an established direction of gene transfer: from organelles to the nucleus researchers understand that a total of 1500 genes have been transferred from the genome of the mitochondria to genome of the nucleus (the 1500 genes have been moved from the mitochondrial chromosomes to the nuclear chromosomes) the movement of genes from the nucleus to organelles is quite rare there is only one known example of a nuclear gene found within the nucleus of plant cells that has been transferred to the chromosomes within the mitochondria of these plant cells the consistent and established transfer of genes from organelles to the nucleus and never vice versa helps to explain the small size of organelle genomes today there is also the possibility of genes being transferred bw two organelles the process of gene transfer can occur bw: - 2 mitochondria - 2 chloroplasts - a chloroplast and a mitochondrion

chicken cell experiment

there was a particular experiment involving chicken cells that was implemented IN THIS EXPERIMENT that probably has to do with the view ability of discrete chromosome territories (the nuclear matrix's method by which it organizes the chromosomes found within the nucleus) CHICKEN CELLS WERE EXPOSED TO A MIXTURE OF PROBES these chicken cells were exposed to a mixture of probes these chicken cells were exposed to a mixture of probes that were able to RECOGNIZE MULTIPLE SITES ALONG SEVERAL OF THE LARGER CHROMOSOMES FOUND IN THE CHICKEN SPECIES that these cells were taken from the probes that these chicken cells were exposed to had the ability to detect specific sequences, multiple sites along several of the larger chromosomes within these chicken cells belonging to a. particular species this particular chicken species was designated as GALLUS GALLUS this particular chicken species was designated as GALLUS GALLUS the probes that these chicken cells were exposed to LABEL EACH TYPE OF METAPHASE CHROMOSOME WITH A DIFFERENT COLOR the probes that these chicken cells were exposed to are responsible for labeling each type of metaphase chromosome with a different color each type of metaphase chromosome found within these chicken cells (due to their placement in a particular set of probes) was labeled with a different color by these probes that were able to recognize multiple specific sites and sequences on the larger chromosomes within the cells of this particular gallus gallus chicken species the metaphase chromosomes within these chicken cells, the different types of metaphase chromosomes within ease chicken cells were labeled with different colors by the probes that these chicken cells were placed in there if figure 10.19b, that showcases the use of the same probes that were used initially to surround the chicken cells and label the different types of metaphase chromosomes within these chicken cells different colors these same probes were utilized when the chicken cells were in interphase when the chicken cells are in interphase, this is a phase of the cell cycle where the cells contains CHROMOSOMES THAT ARE LESS CONDENSED LESS COMPACTED, and these chromosomes are found within the cell nucleus each chromosome in the cells in interphase occupy their own distinct territory, their own distinct and designated chromosome territory

experiments with pneumococcus

there were experiments implemented with pneumococcus there were experiments implemented with pneumococcus there were experiments implemented with pneumococcus there were experiments implemented with pneumococcus, and these experiments implemented with pneumococcus indicated that dna is the genetic material these experiments implemented with pneumococcus suggested that DNA is indeed the geneticmateiral these experiments implemented with pneumococcus suggested that DNA ins indeed the genetic material these experiments implemented with pneumococcus suggested that DNA is indeed the genetic material these experiments implemented with pneumococcus suggested that DNA is indeed the genetic material experiments with pneumococcus suggested that dna is indeed the genetic material there was some early work implemented in microbiology there was some early work implemented in microbiology there was some early work implemented in microbiology there was some early work implemented in microbiology this early work that was implemented in microbiology was important in developing an experimental strategy to identify the genetic material the early work that was implemented in microbiology was integral to developing an experimental strategy to develop the genetic material the early work that was implemented in microbiology was integral to developing an experimental strategy to develop the genetic material Frederick Griffith in particular studied a type of bacterium known then as pneumococci now that bacteria that Frederick Griffith studied, that he identified as pneumococci, is now known and designated as Streptococcus pneumonia Streptococcus pneumoniae is a type of bacterium that Frederick Griffith studied streptococcus pneumoniae is a type of bacterium that Frederick Griffith studied streptococcus pneumonia is a type of bacterium that Frederick Griffith studied there are certain strains of streptococcus pneumoniae that secrete a polysaccharide capsule there are certain strains of streptococcus pneumonia that secrete a polysaccharide capsule there are certain strains of streptococcus pneumoniae that secrete a polysaccharide capsule there are certain strains of streptococcus pneumonia that secrete a polysaccharide capsule there are certain strains of streptococcus pneumoniae that secrete a polysaccharide capsule whereas other strains of streptococcus pneumoniae do not secrete this polysaccharide capsule when streptococcus pneumoniae are streaked onto petri plates containing a solid growth medium: the capsule secreting strains of streptococcus pneumonia hav ea smooth colony morphology the non capsule secreting strains of streptococcus pneumoniae, the strains of streptococcus pneumoniae that do not secrete the polysaccharide capsule have a rough colony morphology when streptococcus pneumoniae strains are streaked onto petri plates that contain a solid growth medium: the strains that do secrete the polysaccharide capsule will showcase a smooth morphology the strains that do not secrete the polysaccharide capsule will showcase a rough morphology the different forms of S. pneumoniae also affect their virulence, or their ability to cause disease the different forms of S. pneumoniae also affect their virulence, or their ability to cause disease the different forms of S. pneumoniae also affect their virulence, or their ability to cause disease the different forms of S. pneumoniae also affect their virulence, the virulence of these strains, the ability of these strains of streptococcus pneumoniae to cause disease the virulence of these strains, the ability of these strains of streptococcus pneumoniae to cause disease the virulence of these strains, the ability of these strains of streptococcus pneumoniae to cause disease, the virulence of these strains, the ability of streptococcus pneumoniae to cause disease, the virulence of these strains, the ability of streptococcus pneumoniae to cause disease is affected by whether or not a particular strain secretes a polysaccharide capsule or not, and the resulting morphology of these strains when they are plated on a solid growth media when smooth strains of streptococcus pneumoniae infect a mouse (recall that smooth strains of streptococcus pneumonia are the strains that do indeed release a polysaccharide capsule, and therefore, when plated on a solid growth medium, have a smooth colony morphology when smooth strains of streptococcus pneumonia infect a mouse (recall that the smooth strains of streptococcus pneumoniae are the strains that do indeed release a polysaccharide capsules nd therefore when plated on a solid growth medium, exhibit a smooth colony morphology), when these smooth strains of streptococcus pneumonia infect a mouse, the capsule the polysaccharide capsule that they secrete allows the bacteria to escape attack by the mouse's immune system the capsule the polysaccharide capsule that a particular strain of streptococcus pneumoniae secretes allows this particular strain of streptococcus pneumonia that secretes this polysaccharide capsule to escape attack by the mouse's immune system when this particular strain of streptococcus pneumonia is injected into a mouse's system, due to its ability to secrete a polysaccharide capsule, this particular strain of bacteria is able to escape attack by the mouse's immune system this particular strain of streptococcus pneumoniae, a strain of bacteria that releases a polysaccharide capsule and therefore showcases a smooth morphology when it is plated on a solid growth medium, is able to avoid attack from the mouse's immune system due to the polysaccharide capsule that it secretes as a result of this particular strain of streptococcus pneumonia releasing this polysaccharide capsule and therefore being able to escape attack by the mouse's immune system, this strain is able to propagate the bacteria of this particular polysaccharide capsule releasing strain is able to propagate and grow within the mouse, eventually killing the mouse in contrast the strain of streptococcus pneumoniae that does not secrete a polysaccharide capsule and therefore presents with a rough colony morphology when it is plated upon a solid growth medium is not able to propagate within a mouse and escape attack by the immune system, strains of streptococcus pneumoniae that do not secrete a polysaccharide capsule and therefore present with a rough colony morphology when they are plated on a solid growth medium will be destroyed by the mouse's immune system, and therefore will not propagate and will not be able to grow, infect, and eventually kill the organism in 1928, Griffith conducted experiments that involved the injection of live and/or heat-killed bacteria into mice in 1928 Griffith conducted experiments that involved the injection of live and/or heat-killed bacteria into mice in 1928 Griffith conducted experiments that involved the injection of live and/or heat-killed bacteria into mice in 1928 Griffith conducted experiments that involved the injection of live and/or heat killed bacteria into mice in 1928 Griffith implemented experiments that involved the injection of live and/or heat killed bacteria into mice live and/or heat killed bacteria was injected into mice through these implemented experiments after injecting the mice with live and/or heat-killed bacteria, Griffith observed whether or not the bacteria that he injected caused a lethal infection after injecting the mice with live and/or heat killed bacteria, Griffith observed whether or not the bacteria that he injected (it was live and/or heat-killed bacteria) caused a lethal infection after injecting the mice with live and/or heat killed bacteria, Griffith examined the mice and observed whether or not the bacteria that he injected into the mice caused a lethal infection in them or not Griffith was working with two distinct and different strains of Streptococcus pneumoniae Griffith was working with two distinct and different strains of Streptococcus pneumoniae Griffith was working with two distinct and different strains of Streptococcus pneumoniae Griffith was working with two distinct and different strains of Streptococcus pneumoniae these two strains of Streptococcus pneumoniae were a type S (s for smooth, meaning that this strain of bacteria when plated and spread on a solid growth medium presented in smooth colonies, and therefore did produce the polysaccharide capsule) and a type R (R for rough, meaning that this strain of bacteria when plated and spread on a solid growth medium presented in rough colonies, and therefore did not produce the polysaccharide capsule) when injected into a live mouse, the type S bacteria proliferated and propagated within the mouse's bloodstream and ultimately killed the mouse when injected into a live mouse, the type S bacteria proliferated and propagated with the bloodstream of the mouse and ultimately killed the mouse when injected into a live mouse, the type S bacteria proliferated and propagated within the bloodstream of the mouse and ultimately killed the mouse when the S strain of streptococcus pneumoniae was injected into a live mouse, it was able to propagate and proliferate within the bloodstream of the mouse due to its secretion of a polysaccharide capsule that allows this particular strain to escape attack from the immune system, and the S strain of streptococcus pneumoniae ultimately killed the mouse following the death of the mouse injected with the S strain of streptococcus pneumoniae, the strain of streptococcus pneumoniae that secretes a polysaccharide capsule that allows it to escape attack from the organism it is trying to infect's immune system and has this particular strain presenting in smooth colonies when it is plated on a solid growth medium, Griffith found many type S bacteria within the mouse's blood when Griffith injected the mouse with a particular stain of streptococcus pneumoniae, when Griffith injected this mouse with the S strain of streptococcus pneumoniae that secretes a polysaccharide capsule that enables this particular strain to escape attack from the immune system that it is trying to infect (and the strain that presents in smooth colonies when it is plated and spread on a solid growth medium), this particular strain of streptococcus pneumoniae, this S strain of streptococcus pneumoniae escaped attack from the immune system of the mouse injected with this particular strain of bacteria, managed to propagate, proliferate, and spread throughout the bloodstream of the mouse and ultimately kill the mouse and in this mouse immediately following its death, Griffith found many type S bacteria within the mouse's blood in contrast, when type R bacteria, a strain of streptococcus pneumoniae that does not secrete a polysaccharide capsule and therefore cannot escape the attack of the immune system of the organism it is attempting to infect (and also presents in rough colonies when it is plated and spread on a solid growth medium), when this particular strain type R of streptococcus pneumoniae was injected into a mouse, the mouse lived in order to verify that it was specifically the proliferation of the smooth bacteria that was causing the death of the mouse in order to verify that it was specifically the proliferation of the smooth bacteria that was causing the death of the mouse, Griffith killed the smooth bacteria, and injected this heat killed smooth bacteria into the mouse the heat killed smooth bacteria was not able to proliferate and therefore the mouse also survived in this scenario, when the s bacteria was killed through the implementation of heat treatment and therefore was no longer able to function and propagate

semilethal alleles

these are alleles that can cause the death of an organism but only to particular individuals within a population looking at a population of individuals and a semi lethal allele amongst them, some individuals will be afflicted with this allele and die, and some will be afflicted but not die the reasons for semilethality are not known in an extraordinarily verifiable manner however the reasons are considered to be: -environmental conditions -the actions of other genes the organism has the actions of the above can result in the detrimental effects potentially being blocked, and therefore the organism, despite the presence of the lethal allele will not die, as opposed to an organism in a different set of environmental factors and/or non-interfering/detrimentally interfering genes who will have that semilethal allele expressed and unfortunately die an example of a semilethal allele the X-linked white-eyed allele (this allele is described in Ch. 3) depending on the growth conditions of different Drosophila melanogaster flies, 1/4 to 1/3 of these flies that would be expected to exhibit the phenotypic trait of white eyes coded for by this X-linked allele would die prematurely (once again due to the environmental conditions the larva are allowed to grow in, vs the ones that will result in the expression of the semilethal allele, and which environment these larva are put in)

ovules

these are formed in the ovaries of the plant, and within the ovules, female gametes (eggs) are found

characters

these are known as the general characteristics of an organism with the peas that he bred, he made sure they were all distinct, very different from one another morphologically, but still belonging to the same species so that they could fertilize one another while still being markedly different in appearance

conditional lethal alleles

these are lethal alleles that only express themselves and cause the death of an organism when there is the presence of particular environmental conditions conditional lethal alleles have been researched extensively in experimental organisms (where you can control the environment an organism is in and see if that triggers a particular allele to express itself, and cause the death of that organism) an example of a conditional allele is one that will express itself and cause the death of an organism when the organism is in a particular temperature range these alleles are designated as TEMPERATURE-SENSITIVE (TS) LETHAL ALLLES these alleles are found in many organisms, one species that these temperature sensitive lethal alleles are found in is Drosophila melanogaster the temperature sensitive lethal allele in Drosophila melanogaster will express itself and cause the death of an organism if larva are developing at a temperature of 30 degrees celsius or above the larva will develop appropriately and the temperature sensitive lethal allele will not be expressed if the larva are developed at a lower temperature of 22 degrees celsius how do temperature sensitive lethal alleles come about? temperature sensitive lethal alleles usually function in the way that the mutated allele is caused by mutations that change the structure of the protein the allelic combination/gene is coding for therefore the protein is unable to function at particular temperatures (due to these mutations causing alterations in its structure), and if this protein is exposed to those temperatures it is unable to function at, then the protein will either simply not function or unfold and rapidly degrade (therefore the protein is lost and there is no hope of it regaining functionality) conditional lethal alleles can also be identified due to and influenced by other environmental conditions (conditions other than temp) such as environmental agents an example of this: individuals with a defect in the gene that codes for the enzyme glucose-6-phosphate dehydrogenase (G6PD) so if there is a defect in the gene coding for this enzyme glucose-6-phosphate dehydrogenase, then the individuals with this gene defect will have a negative biological reaction to the ingestion of fava beans (fava beans serve as the environmental agent resulting in the functionality of a conditional lethal allele) if the individual with this gene defect ingests fava beans, then they can possibly be afflicted with acute hemolytic syndrome there is a 10% mortality rate for acute hemolytic syndrome if left untreated

chromosomes

these are structures within living cells, these are structures within living cells that reside in the nucleus and contain genetic information (as they are composed of DNA and chromatin) genes are physically located within the chromosomes, on the chromosomes (you are able to see where certain genes are on a particular chromosome through banding patterns that one can identify demarcating a space and a band for every segment of DNA encoding a gene on a chromosome BIOCHEMICAL breakdown of what constitutes a chromosome: what constitutes a chromosome: A VERY LONG SEGMENT OF DNA DNA is the genetic material that the chromosomes contain and are made up of, a v long segment of DNA composes chromosomes chromosomes are also made up of proteins these proteins that chromosomes are composed of are bound to DNA the proteins that the chromosomes are composed of that are bound to the DNA are bound to the DNA bc they provide the DNA with an organized structure to adhere to the complex bw the DNA and the proteins that are bound to the DNA giving it organized structure is called chromatin within Ch. 3 the focus will be on the cellular mechanisms of chromosome transmission (how cells transmit chromosomes from generation to generation of daughter cells) and understand on a cellular level how those patterns of inheritance we learned about in Ch. 2, the Mendelian patterns of inheritance, come into play on the cellular level WE ARE SPECIFICALLY LOOKING AT how chromosomes are copied during the synthesis phase, and then sortied into newly synthesized cells

chromosomes

these are the structures within cells, these structures found within cells (within the nucleus of eukaryotic cells or the nucleoid region of prokaryotic cells) contain the genetic material of an organism

genotypic ratio vs. phenotypic ratio

these can be markedly different, due to the genotypic ratio having to do specifically with the allelic combinations, and the phenotypic ratio having to do with the presented traits there can be multiple genotypes that lead to the same trait, so the genotypic ratio will differ from the phenotypic ratio example: TT and Tt are two different genotypes, but they both result in a tall plant, therefore the genotypic ratio amongst the offspring will differ from the phenotypic ratio amongst the offspring

nonessential genes

these genes are not absolutely necessary for an organism to live however they will probably be coding for the phenotypic expression of traits beneficial to the organism if there is a loss of function mutation in a nonessential gene, where whatever its coding for is lost due to the mutation that causes the gene and by proxy whatever that gene is phenotypically expressing to cease in its functionality however, there can be a scenario in which a nonessential gene acquires a mutation this mutation that the nonessential gene acquires can cause the product coded for by this gene to be abnormally expressed this product can be abnormally expressed to the degree that it interferes with the normal functionality of the cell this can cause a lethal phenotype and the possible death of the organism so lethal mutations usually occur in essential genes (therefore the loss of function mutation in these necessary genes is fatal, bc if they lose their functionality due to a mutation, we lose the product they code for that is necessary for the organism's life) but lethal mutations can also occur in nonessential genes, where it can alter the expression of a gene product to a degree that it interferes fatally with the body

several types of Mendelian inheritance patterns

these have been observed by researchers these are situations where the expression of a trait is influenced by a gene with two alleles, however, it is also influenced by a variety of other factors the two goals: 1) we want to understand how the molecular expression of genes can influence the way a trait is expressed, the morphological, physiological, and behavioral phenotype of the individual, we want to see the relationship bw molecular genetics and phenotypic expression in an individual recall that molecular genetics is the study of how the expression of genes leads to the production of function proteins that carry out processes that result in the expression of a phenotypic trait 2) the outcome of various types of crosses a lot of the crosses we observe in the table do not result in a 3 to 1 phenotypic ratio, even when there are two heterozygotes reproducing (according to Mendelian genetics, this should result in a 3:1 phenotypic ratio amongst the offspring of this course, but as we can see that is not the case)

Mendel's laws of inheritance

these laws of inheritance contribute greatly to the studies of laws of inheritance for -fruit flies -corn -roundworms -mice -humans the laws of inheritance that he established through his experimentation with pea plants apply to all of the above organisms that's why the pea plants can be considered model organisms

gain of function mutation

these mutations (gain of function mutations) change the gene itself, or the protein coded for by the gene in order to have the gene or specifically /directly the protein gain a new or abnormal function, a function that it did not have before (so perhaps the gene will now code for something new/different, or the protein will do a different function an example of a mutant gene with a gain of function mutation is that the mutant gene to to changes in its genetic code may be over expressed, and therefore produce too much of the encoded protein

trait/variant

these terms are utilized in order to describe the specific property of a character (the specific properties of the general characteristic of an organism)

sexually reproducing species genetic makeup

they are normally diploid, having 2 copies of each chromosome, 1 of each set from either parent (essentially 1 set of 23 from the father, 1 set of 23 of the mother) the copies of chromosomes are known as homologs of each other, because they code for the same traits, but within the traits they code for, there can be variation in the alleles of the gene, the allelic combination that determines the trait the the gene is coding for i.e., two homologs would have a gene on both of them coding for hair color, but one might have the dominant allele for brown and the other the recessive allele for red, and there will be an allelic combination showing the brown dominant allele winning out and the offspring being brunette the exceptions to this rule are the x and Y chromosomes in males, they are not homologs of one another and in fact code for different things

null hypothesis

this assumes that there is no real difference bw the observed and expected values, the data observed and the data expected according to the null hypothesis, any discrepancies that occur are due to random sampling error

maternal effect

this designates an inheritance pattern for particular nuclear genes nuclear genes- these are genes located on chromosomes found in the cell nucleus the maternal effect is a pattern of inheritance in which the genotype of the mother directly impacts and determines the phenotypic trait that her offspring express in this pattern of inheritance, the genotype of the father as well as the genotype of the offspring themselves do not affect the phenotypic trait that the offspring express the mother is the sole determinant of the phenotypic traits that the offspring express the father makes no contributions to the phenotypic expressions of the offspring, has no influence/impact on the morphology of the offspring despite contributing genetic material even if the allelic combination of the offspring (according to Mendelian genetics) should result in the expression of the phenotype that differs from the one the mother determines, the offspring will express the phenotype that the mother determines this phenomenon is explained by the accumulation of gene products (the conglomeration of products coded for by genes) in the developing eggs of the mother the first example of the maternal effect was studied by Arthur Boycott 1920s Arthur Boycott examined the morphological features (the phenotypic presentation) of the water snail- Lymnaea pereira with the water snail species Lymnaea pereira, their shells and internal organs can be arranged in a right-handed (dextral) or left-handed (sinistral) direction right-handed direction= dextral left-handed direction= sinistral the right handed direction (dextral) is more common, the wild-type dominant trait) the left hand direction (sinistral) is less common and a more recessive trait Arthur Boycott implemented a genetic analysis on these water snails he began with two true-breeding strains that presented differently morphologically (different phenotypic expressions, so a true-breeding dextral and true-breeding sinistral strain) he found many results that did not align with Mendelian patterns of inheritance the first portion of the experiment (the initial cross bw the two true-breeding strains of dextral and sinistral water snails) aligned with Mendelian patterns of inheritance for example, when a dextral female (DD so homozygous dominant for the dextral shell and internal organs) was crossed to a. sinistral male (dd, so homozygous recessive for the sinistral shell and internal organs) however, in the reciprocal cross (where the sexes and corresponding phenotypes were switched) and a sinistral female (dd- homozygous recessive for a sinistral conformation of shell and organs) and a dextral male (DD homozygous dominant for a dextral shell and internal organs) were crossed with one another, all of the offspring were sinistral (despite sinistral being the recessive trait, and Mendelian genetics detailing that due to the cross bw a homozygous dominant dextral male and a homozygous recessive sinistral female, all of the offspring should showcase the dominant, common, wild-type dextral shell and internal organs trait) how is this possible that the experiment completely contradicted the Mendelian inheritance patterns? Alfred Sturtevant proposed the idea that snail coiling (having a dextral or sinistral shell and internal organs) is influenced by a maternal effect gene this maternal effect gene exists as a dextral (D- the dominant allele coding for a dextral shell and internal organs) or a sinistral (d- the recessive allele coding for a sinistral shell and internal organs) he came to this conclusion due to the inheritance patterns he found in the F2 and F3 generations the genotype of the F1 generation (resulting from a cross bw a true breeding dextral female and a true breeding sinistral male) was expected to result in a heterozygous genotype (according to the patterns of Mendelian inheritance) when these heterozygous individuals of the F1 generation were crossed with one another, there was an expected genotypic allelic combination conglomeration of 1 DD to 2 Dd to 1 dd according to Mendelian patterns of inheritance and the governing principles of Mendelian genetics, due to the D allele for dextral shells and internal organs being dominant to the d allele for sinistral shells and internal organs, any allelic combination containing the D allele should result in the individual with this allelic combination (containing the D allele coding for dextral shells and internal organs) presenting with a dextral shell the expected phenotypic ratio of the F2 generation was 3 dextral to 1 sinistral however, the entire F2 generation was composed of dextral snails (contradicting the predicted allelic combinations and the corresponding phenotype predications) the phenotypic presentation of the F2 generation aligns with the principle of the maternal effect (it follows this very unusual non-Mendelian inheritance pattern) the phenotype of the offspring depended completely upon the genotype of the mother, the mother's contributions, the allelic combination of the mother was the only determinant of the offspring's phenotypic expression an example of how the genotype of the mother is the sole influence of the offsprings' phenotypes: the F1 mothers were Dd in this allelic combination containing the dominant D allele coding for dextral and the recessive d allele coding for sinistral, the D allele dominates over the d allele, and this allelic combination of the mother causes the offspring to be dextral, even if their allelic combination contradicts that (for example, even if they have the homozygous recessive allelic combination dd that should code for a sinistral shell, they will have a dextral shell due to the Dd allelic combination of the mother that codes for a dextral shell) when members of the F2g generation were crossed there was a 3:1 ratio of dextral: sinistral in the F3 generation the ratio of F2 females was 1 DD (dextral): 2 Dd(dextral): 1 dd(sinistral) this phenotypic ratio of 3 dextral to 1 sinistral found within the F3 generation corresponds to the phenotypic ratio within the F2 generation females that bred with males in order to create the F3 generation the DD and Dd females (their allelic combinations both coding for dextral shells) produced all dextral offspring, regardless of the genotype/allelic combination and phenotype of the male they bred with the dd females (their allelic combination coding for sinistral shells and internal organs) produced all sinistral offspring regardless of the genotype/allelic combination and phenotype of the male they bred with the corresponding and match of the ratios of F2 females to the ratios of all the offspring in the F3 generation indicates the maternal effect occurring, where the mother's genotype is the sole determinant of the phenotype of the offspring

genetics

this discipline encompasses: -molecular -cellular -organism -population biology geneticists usually focus on model organisms model organisms are organisms studied by lots and lots of researchers, and these researchers compare their results and see if they can determine broader scientific principles they utilize these model organisms and their research on them in order to establish principles that can apply to other species as well common examples of model organisms: Escherichia coli (a bacterium) Sacharomyces cervisiae (a yeast) Drosophila melanogaster (fruit fly) Caenorhabditis elegans (a nematode worm) Danio rerio (zebra fish) Mus musculus (mouse) Arabidopsis thaliana (a flowering plant) there are experimental advantages to model organism E. coli is a v simple organisms that can be really easily grown in a laboratory, easy to propagate in order to study and establish broader principles through multiple research projects limiting the work to a few model organisms is v important in order to easily unravel the genetic mechanisms, the governing principles that control the traits of multiple species

binomial expansion equation

this equation can be used to predict the probability of an unordered conglomeration of events (so a totality of events not occurring in any particular order) an example of this is a cross bw two heterozygous brown-eyed individuals we are trying to figure out the probability that 2/5 of their children will have blue eyes, not in any particular order

experiment done in order to conclude that in adult female mammals, there is one X chromosome that has been inactivated permanently

this experiment is based off of the Lyon hypothesis the Lyon hypothesis is a hypothesis detailing that within each somatic cell of female mammals specifically, the genes are expressed on only one of the present X chromosomes, not both of them therefore, if an adult female is heterozygous for an X-linked gene (a gene that is found on the X chromosome and is often influenced by an allelic combination for that gene consisting of two alleles, one on the first X chromosome, and on the other), only one of the two alleles they have in their heterozygous allelic combination will be expressed in every one of their somatic cells, as one X chromosome in each cell will be inactive, and none of the genes on this X chromosome will be expressed there were 3 individuals in 1963 who wanted to test out the Lyon hypothesis, and experiment with it at the cellular level: - Ronald Davidson - Harold Nitowsky - Barton Childs the experiment they implemented in order to test the Lyon hypothesis hound in on an X-linked gene within humans that encodes an enzyme that is involved in the process of sugar metabolism this enzyme that is involved in the process of sugar metabolism is glucose-6-phosphate dehydrogenase (G-6-PD) before the Lyon hypothesis was proposed by Mary Lyon, biochemists had discovered that individuals vary in regards to the G-6-PD enzmye a researcher is able to detect these variations in regards to the G-6-PD enzyme that occur from human to human when the G-6-PD enzyme undergoes gel electrophoresis (recall that G-6-PD is involved with the process of sugar metabolism and is designated as glucose-6-phosphate dehydrogenase through exposing different individual's G-6-PD enzymes to gel electrophoresis, it was determined that there is one allele for the G-6-PD gene that codes for a G-6-PD (glucose-6-phosphate dehydrogenase) enzyme that moves very quickly across the gel during gel electrophoresis there is another allele of the G-6-PD that codes for a G-6-PD enzyme that moves more slowly across the gel during gel electrophoresis a sample of cells that was taken from heterozygous adult females showed both types of enzymes produced (the enzymes that move quickly across the gel during gel electrophoresis and the enzymes that move slowly across the gel during gel electrophoresis) so the sample of cells taken from heterozygous adult females showed both types of the G-6-PD enzymes a sample of cells taken from hemizygous adult males produce either the fast or slow type of the G-6-PD enzyme, but not both the reason that there is a difference between the speed of the G-6-PD enzymes (the reason that one is fast and one is slow) is due to a difference in the structure of these two enzymes the minor differences bw the fast and slow G-6-PD enzymes that makes them move either quickly or slowly across the gel during gel electrophoresis does not affect the function of the G-6-PD enzyme however the differences bw the fast and slow G-6-PD enzymes allow geneticists to distinguish bw the two different G-6-PD enzymes, and therefore distinguish bw the two different G-6-PD gene alleles that codes for these two different g6pd enzymes the Lyon hypothesis was tested using cell culturing techniques (cell cultures were utilized in order to test the Lyon hypothesis and its theory of X-inactivation being the cause of highly condensed Barr bodies within the somatic cells of female mammals as well as the patchwork phenotypic expression of coats within females and the lack of this patchwork pattern within males occurring within different species) this Lyon hypothesis was tested by: -Davidson -Nitowsky -Childs these above experimenters removed small samples of epithelial cells from a female with a heterozygous allelic combination and grew them in a laboratory (so they took epithelial cells from a heterozygous female and grew cell cultures filled with these cells) when the samples from the heterozygous female were combined, the combined sample contained a mixture of both types of G-6-PD enzymes (both the enzymes that moved quickly across the gel during gel electrophoresis and the enzymes that moved slowly across the gel during gel electrophoresis) the reason there was this mixture, a mixture of cells taken from a heterozygous female containing both fast and slow enzymes when examined, is because all of the adult cells collected (and then combined) stemmed from different embryonic cells (during embryogenesis, there is the possibility of having multiple embryonic cells, and different lines of somatic cells stemming from these multiple embryonic cells therefore if the embryonic cells have different genotypes, that will result in collections of somatic cells with distinct and marked differences in their genotypes (having the same genotype as the respective embryonic cells they stemmed from, and due to the difference in the genotype of the embryonic cells they stemmed from, they mimic and maintain this difference in their genotypes) some of the somatic epithelial cells collected from the heterozygous female stemmed from an embryonic cell with the allele coding for a slow G-6-PD enzyme, and some of the somatic epithelial cells collected from the heterozygous female stemmed from an embryonic cell that had the allele coding for the fast G-6-PD enzyme during an additional experiment, the somatic epithelial cells collected from the heterozygous female, and are sparsely plated onto solid growth media (so not a lot of them are plated onto solid growth media for them to proliferate) after leaving those cells sparsely plated onto solid growth media, each cell plated onto the solid growth media undergoes after several days, a colony of cells is produced, as each individual cell has undergone mitosis and therefore through this process of cell division, proliferated a colony of cells is also known as a CLONE of cells, and this is because all of the cells found within a colony were derived from a single origin cell, and therefore are all clones of the original cell they proliferated from the point of designating a colony of cells as a clone is to recognize that all of the cells within a colony proliferated from the same origin cell the hypothesis that the researchers had due to their knowledge of colonies/clones the researchers reasoned that all cells within a single clone would express only one of the two G-6-PD cells (either the fast or slow one, either the fast or slow moving G-6-PD enzyme) due to the cell having to originate from an embryonic cell which only had an allele coding for either the slow or fast G-6-PD enzyme (therefore all cells stemming from that origin embryonic cell will also have only the allele coding for the enzyme that the original cell had an allele coding for) the scientists grew 9 colonies/clones (so they grew 9 collections of cells, all from the same organism, but unsure of which embryonic cell coding for which enzyme- fast or slow- they stemmed from) the 9 colones/clones were grown within liquid cultures the cells were then lysed in order to release the G-6-PD enzyme (they were burst in order to release the G-6-PD enzyme within them) these proteins were then subjected to the process of sodium dodecyl sulfate (SDS) gel electrophoresis in order to see whether or not the G-6-PD enzyme moves fast or slow across the gel when it is subjected to gel electrophoresis the hypothesis of the researchers was the following: an adult female that is heterozygous: an adult female who is heterozygous for the fast and slow G-6-PD alleles (so an adult female had an allelic combination of an allele coding for a fast G-6-PD enzyme, and an allele coding for a slow G-6-PD enzyme) should express only one of the two alleles in any given one of her somatic cells (either the allele coding for the fast G-6-PD enzyme, or the allele coding for the slow G-6-PD enzyme), as well as any descendants of this somatic cells (any cells that proliferated from the one examined due to mitosis) however no somatic cell within this heterozygous female can have both alleles coding for both fast and slow G-6-PD enzymes

transmission genetics

this field of genetics explores the heredity of traits, the inheritance of them by offspring from their parents; traits being passed down from generation to generation the analysis of transmission of genes from parent to offspring the outcome fo the offspring's traits is also analyzed, how the traits are presented in the offspring, and how those traits were inherited and presented in the individual an example of transmission genetics analysis is two brown-eyed parents producing a blue-eyed child another example is tall offspring tending to produce tall children the studies of Gregor Mendel assisted in our modern understanding of transmission genetics Gregor Mendel originated the widespread and confirmed concept that factors (that we now designate as genes) are passed as discrete units from parents to their offspring these genes are passed through the mechanism of sperm and egg cells containing the chromosome with those genes genetic studies were pioneered in the 1860s the genetic patterns of inheritance are far more complicated than simple mendelian inheritance patterns

X-linked

this inheritance pattern involves the inheritance of genes that are found solely on the X chromosome, they are coding for allosomal traits within mammals and fruit flies: males are hemizygous for x-linked genes, they have one X chromosome and one Y chromosome, and therefore for the x linked gene, they only have one allele, the one located on the X chromosome, that influences the expression of the phenotypic trait and can not be combated by the presence of any allele on the Y chromosome, as the trait is x-linked, and therefore there are no genes on the Y chromosome contributing to the expression of this trait females have two copies of the X-chromosome, where therefore there will or can be an allelic combination, where there are two alleles working together to express one phenotypic trait (homozygous dominant/recessive) or battling against one another (heterozygous) Molecular: if there is a pair of x-linked alleles (an allelic combination for an x-linked gene) with a dominant/recessive mendelian relationship, then if there is 50 percent of the protein being produced, due to the presence of a single copy of the dominant allele in the allelic combination, then that will be enough to produce the dominant trait recall that this interaction and influence of the dominant allele over the recessive one when it comes to the X chromosome can only occur within females due to their possession of 2 X chromosomes

cytogenetics

this is a field of genetics (so a field found under the umbrella of genetics) this particular field involves the microscopic examination of chromosomes within this field of genetics, cytogenetics, the microscopic examination of chromosomes occurs, chromosomes are analyzed under a microscope researchers have been able to gain insight into patterns of inheritance by observing chromosome under a microscope CYTOGENETICIST- a researcher in the field of cytogenetics the most basic of observations that a cytogeneticist can make when looking at chromosomes underneath a microscope is to is to examine THE CHROMOSOMAL COMPOSITION OF A PARTICULAR CELL the most basic process a cytogenecist can implement is looking at and analyzing the chromosomal composition of a particular cell, they can look at the chromosomes within a particular cell and arrange them into a karyotype and analyze them to understand the genetic composition of that individual, and perhaps clues to governing genetic characteristics of the species that that individual belongs to (perhaps the number of chromosomes they all have, which chromosomes, if any define their sex) when cytogeneticists are observing eukaryotic species, they accomplish the chromosomal composition of this species' eukaryotic cells by observing the chromosomes in a particular state they observe the chromosomes of these cells at particular state, the chromosomes as they present during a particular phase (prophase or metaphase) of mitosis when a cell is preparing to divide (during prophase and metaphase is when this occurs) they become compacted and tightly coiled this compaction and coiling makes the crumpled up DNA shorter and with a thicker diameter, taking on the distinctive shape of the chromosome we know and love today this compaction and coiling occurs during prophase and metaphase (the chromosomes are at their highest compaction during metaphase) the consequence of this shortening due to the compaction and coiling of the jumbled DNA during prophase and metaphase is that now, the cytogeneticist will be able to see DISTINCTIVE SHAPES AND NUMBER OF CHROMOSOMES with a light microscope with a light microscope, they are able to see distinctive shapes and numbers of the chromosomes that form due to the compaction and coiling that takes place during prophase and metaphase of mitosis every species has a particular chromosomal composition, a particular number of chromosomes that you will find within every one of its somatic cells the majority of human cells, the majority of human somatic cells contain 46 chromosomes, and within that 23 pairs of chromosomes (2 per pair) so within human somatic cells, the majority of their cells, they have 23 pairs of chromosome, each pair having 2 chromosomes each, making for a total of 46 chromosomes per somatic cell (23 of these chromosomes, 1 entire set of all the types of chromosomes is maternally inherited, the other 23 chromosomes, the other entire set of chromosomes is paternally inherited) there rare occasions where a human individual will not have the requisite common number of 46 chromosomes, and instead of inheriting 23 chromosome maternally and 23 chromosomes paternally, will inherit an abnormal number of chromosomes individuals are also able to inherit abnormal chromosomes in regards to their structure containing mutations (inheriting mutated chromosomes) these abnormalities in either chromosome number or the structures of the chromosome themselves by looking at the chromosomes within an individual's somatic cell under a microscope this microscopic examination of the chromosomes within an individual's somatic cells must occur on the chromosomes of actively dividing cells, chromosomes from cells that are undergoing mitosis so that the chromosomes are properly compacted and coiled to the point that they can be detected and distinguished through the usage of a light microscope (you want to make sure the point at which you view the chromosomes is when the cell they are contained in is undergoing mitosis, particularly the phase prophase or metaphase, which is when they are highly compacted and therefore highly distinctive and visible)

complementation

this is a genetic phenomenon where there is a production of offspring with a wild-type dominant phenotype however the offspring with this wild type dominant phenotype are produced from parents that display the same or similar recessive phenotype so how do two parents with recessive phenotypes (and presumably homozygous recessive allelic combinations) produce offspring with dominant phenotypes (presumably homozygous dominant allelic combinations)? in the described case, in the first filial generation all offspring had purple flowers, despite being produced by parents with white flowers why does complementation occur? it usually occurs bc the recessive phenotype in the parents is due to the presence of a homozygous recessive allelic combination that is able to masks the phenotypic dominant trait that the homozygous dominant allelic combination is trying to express homozygosity of two different genes and two different allelic combinations interacting the offspring in complementation need to have a dominant allele in both genes and thus both allelic combination in order to display the dominant wild type phenotype so if the allelic combination is CCpp, with one gene having a homozygous dominant allelic combination (1 more dominant allele than necessary) and a homozygous recessive allelic combination (no dominant allele) than the individual with this allelic combination will display the trait the homozygous recessive allelic combination is coding for, which is in this case white flowers if the allelic combination is CcPp, then there is a dominant allele in both genes, in both allelic combinations, and the individual with this allelic combination will display the phenotypic trait that the two dominant alleles in both allelic combinations are coding for, which is purple flowers if researchers see complementation in a genetic cross (an offspring completely phenotypically different in terms of displaying a dominant trait when both parents display a recessive trait), they usually attribute the recessive trait in the parents to mutant alleles found in two different genes, the presence of these mutant alleles (possibly in a homozygous recessive combination that is able to mask the phenotypic effects of dominant alleles)

Duschene muscular dystrophy

this is a human disease, and was first described by the French neurologist Guillaume Duchenne he described Duschene muscular dystrophy in the 1860s individuals affected by Duschene muscular dystrophy (having the allelic combination coding for this condition) show signs of muscle weakness these signs of muscle weakness can manifest as early as age 3 Duschene muscular dystrophy gradually weakens the skeletal muscles of the body eventually this condition of DMD affects the heart and breathing muscles, weakening them individuals affected by DMD rarely survive past their 30s the gene for DMD- this gene is found on the X chromosome the gene for DMD codes for a protein called dystrophin the protein dystrophin is required inside muscle cells and assists with structural support of these muscle cells this protein is thought to strengthen muscle cells by anchoring elements of the internal cytoskeleton of muscle cells to the plasma membrane without the presence of dystrophin in these muscle cells, the plasma membrane (without the attachment of the internal cytoskeleton to the plasma membrane) becomes permeable and can rupture, leading to weak muscle cells and therefore weak muscles DMD Duschene Muscular Dystrophy is inherited in an X-linked recessive pattern the disease is recessive and inherited in a recessive manner, meaning that an individual must be homozygous recessive in order to express the phenotypic trait of DMD the gene and allelic combination within this gene coding for DMD is located on the X chromosome in the pedigree for muscular dystrophy, several males are affected by this disorder the mother of these males are presumed to be heterozygotes for this recessive x-linked allele, where they do not have DMD bc they are heterozygous for it, and the dominant allele coding for an appropriately working dystrophin protein overwhelms the recessive alleles however, their sons when inheriting that allele do phenotypically express DMD, bc they have one x-chromosome with the allele coding for this trait, and there isn't any other allele within this allelic combination to combat this first allele coding for DMD, therefore the allele for DMD wins out automatically due to the lack of a combatting allele the males are all hemizygous for DMD, and therefore the allele coding for DMD wins out always and they have DMD the recessive disorder DMD is very rare bc females have to inherit two alleles coding for DMD in order to phenotypically express DMD the daughters need to inherit a copy of the mutant allele from their mother on the X chromosome they inherit from her and a copy of the mutant allele from the X chromosome they inherit from their father not possible for them to express DMD phenotypically if only one parent is a carrier impossible if neither is a carrier minimally possible if both are carriers completely both if both are affected

degrees of freedom

this is a measure of the number of categories that are indpenednet of each other when phenotype categories are derived from a punnet square (detailing a cross bw two individuals resulting in certain variants of a character), the number is typically n-1 within the example, the number of different phenotypes we get within the second filial generation is 4, so the degrees of freedom is 4-1=3 going off of degrees of freedom, we find the value on the chi square chart that it matches the closest to, and that value of 1.005 is in the 0.80 category, there is an 80 percent probability that any deviation bw the observed and expected results is due to random sampling error the null hypothesis is correct IT DOES NOT PROVE A HYPOTHESIS CORRECT it simply shows as a statistical method whether or not the data and hypothesis fit well together, whether or not there is deviation that would result in the proposed hypothesis not fitting with the experiment and another hypothesis having to be proposed REMEMBER THIS ABOUT THE CHI SQUARE TEST DATA AND HYPOTHESIS FIT NOT WHETHER OR NOT IT IS CORRECT

dominant-negative mutations

this is a mutation in which the protein encoded by the mutant gene acts antagonistically to normal protein coded for by the normal gene so the mutant gene produces an abnormal protein that antagonizes the. normal protein produced by the normal gene within a heterozygous individual, the mutant protein coded for by the mutant allele acts antagonistically and counteracts the effects of the normal protein coded for by the normal allele the mutant protein counteracting the effects of the normal allele leads to the phenotypic trait expression being altered

codominance

this is a pattern showcased by the heterozygote expressing the traits the dominant and recessive allele code for simultaneously an example of the above is blood typing- in which there can be an individual with the allelic combination of A and B, and their blood type due to the codominancem within this allelic combination will be AB blood type Molecular: the codominant alleles (the two alleles within this heterozygous allelic combination) code for proteins that function differently from one another, and therefore both influence the expression of the phenotypic trait in their individuals ways, unfettered by one another

incomplete dominance

this is a patterns that occurs when the heterozygote (the organism containing a gene with one dominant allele and one recessive allele) has a phenotype that is an intermediate bw the phenotypic trait the dominant allele is coding for and the phenotypic trait the recessive allele is coding for you will find the heterozygote to be morphologically, physiologically, behaviorally different from the homozygous dominant and the homozygous recessive an example of the above (incomplete dominance) is that a cross occurs bw a homozygous dominant red-flowered plant and a homozygous recessive white-flowered plant this cross results in heterozygous offspring with pink flowers, an intermediate phenotype bw the dominant red and recessive white Molecular: within a heterozygote, if there is one dominant allele coding for the protein that's expression and function will result in the phenotypic expression for the dominant trait, the 50% expression it contributes as part of a 2 piece allelic combination is not enough for the dominant trait to be expressed the dominant trait can only be expressed with the homozygous dominant individual, where 100% of the protein is produced

over dominance/heterozygote advantage

this is a phenomenon in which a heterozygote may display phenotypic traits that are more advantageous and beneficial for their survival in a particular environment than either of the corresponding homozygotes (homozygous dominant and homozygous recessive individuals) these heterozygotes are more likely to survive due to their advantageous trait and reproduce organisms with the same advantageous trait a heterozygote may be: -larger -disease resistant -more suited to withstanding and surviving harsh environmental conditions essentially, the heterozygote is prone to more survival and reproduction than either homozygous individuals an example of overdominance/heterozygote advantage is sickle cells disease, specifically the human allele that causes sickle cell disease in homozygous carriers sickle cell disease is an autosomal (coded for on a non-sex chromosome) recessive disorder an affected individual (homozygous recessive) will have an altered form of the protein hemoglobin hemoglobin is responsible for carrying oxygen within red blood cells normal individuals with allelic combinations not coding for sickle cell anemia have the allelic combination of HbA (two HbA alleles) coding for hemoglobin A, which properly carries oxygen within red blood cells individuals with allelic combinations coding for sickle cell anemia have the allelic combination HbS, coding for hemoglobin s, which does not properly carry oxygen within red blood cells this causes the red blood cells of these affected individuals to deform into a sickle shape due to low oxygen concentration from the hemoglobin s coding for by the HbS allele not properly carrying oxygen within the individual's red blood cells this sickling phenomenon causes the life span of these underoxygenated red blood cells to be shortened to a few weeks the normal life span of appropriately oxygenated red blood cells is 4 months anemia results from this sickle cell condition abnormally shaped sickle cells can become clogged in the capillaries of the body, conglomerating in particular locations there are then localized areas within the capillaries of the body where there is a lack of oxygen this condition of localized areas in the body having a lack of oxygen is designated as a crisis; pain, and tissue and organ damage can result from a crisis an individual that is homozygous recessive for the HbS allele and therefore is impacts by sickle cell anemia has a shorter lifespan than an individual with an allelic combination coding for hemoglobin A, which properly can carry oxygen within red blood cells there are harmful consequences to homozygotes carrying the dominant allele coding for hemoglobin A and the recessive allele coding for hemoglobin B however, the presence of an allele coding for sickle cell anemia alongside an allele coding for hemoglobin A is common amongst human populations that are exposed to malaria there is a protozoan genus that causes malaria- Plasmodium this protozoan genus spends its life cycle inside of the Anopheles mosquito this protozoan genus plasmodia spends the other portion of its life cycle within the red blood cells of individuals that have been bitten by an Anpholes mosqutio infected by the plasmodium red blood cells of heterozygotes HbAHbS are likely to rupture when they are infected by the parasite plasmodium this stops the plasmodium parasite from propagating within a heterozygous individual therefore people who are heterozygous, containing the dominant HbA allele coding for hemoglobin A and the recessive HbS allele coding for hemoglobin S are unaffected by sickle cell anemia and are malaria resistant the homozygous HbSHbS allelic combination is still detrimental, but the higher survival rates of the heterozygote has resulted in the common presence of the HbS allele within populations exposed to malaria, as in those situations where the population is exposed to malaria, the presence of 1 HbS allele is advantageous to influencing malaria resistance over dominance explains the prevalence and commonality of the sickle cell allele within these populations, the fact that the heterozygous allelic combination is more advantageous than either of the homozygous allelic combinations there are scenarios in which the heterozygous allelic combination is beneficial and both of the homozygous allelic combinations are harmful look at notes for ratios, it is a 1:2:1 ratio, non Mendelian over dominance is usually attributed to two alleles that code for proteins with slightly varied amino acid sequences the resulting question is how do we explain the observation that two protein variants found within a heterozygote (where a heterozygous allelic combinations results in proteins with slightly different amino acid sequences) lead to an individual with a more advantageous phenotype three common explanations for this: 1) with sickle cell anemia, the phenotype being advantageous is related to the infectivity (the degree to which something can successfully infect something else) of the protozoan genus plasmodium in the heterozygous individual due to the allelic combination HbAHbS, the infectious agent protozoan genus plasmodium is less likely to propagate within this organism, due to the red blood cells it infects rupturing before the infection can spread there may be scenarios in which heterozygous allelic combinations can may attribute to disease resistance, but the two homozygous combinations (dominant and recessive) are both detrimental to the organism an example of this is PKU the heterozygous fetus may be resistant to miscarriage caused by a fungal toxin, and either of the homozygous fetuses would not be resistant to miscarriage by this fungal toxin another example is Tay-sachs disease, where the heterozygous individual may be resistant to tuberculosis, while the two homozygotes are not 2) the subunit composition of proteins can explain over dominance sometimes, proteins can function as a complex consisting of a conglomeration of subunit, each subunit of this protein being composed of a polypeptide dimer- a protein composed of two subunits if both of the subunits of this protein dimer are coded for by the same gene, the protein composed of two subunits coded for by the same gene is known as a homodimer homo- this term designates the fact that the two protein subunits come from the same type of gene the gene may exist within different alleles, but these two protein subunits composing a homodimer come from the same gene homozygotes can only produce A1A1 or A2A2 heterozygotes can produce A1A1, A2A2, or A1A2, which appears to be more advantageous than the other two for some proteins, the A1A2 homodimers may have better functionality, resulting in improved and advantageous functional activity due to the A1A2 homodimer being more stable or able to function under a variety of conditions (while the A1A1 and A2A2 homodimer may be more limited in their stability and ability to function in a variety of circumstances the greater activity of the heterozygote in comparison to either homozygote may the underlying reason for the heterozygote being superior to either homozygote, more advantageous 3) the proteins coded for by each allele may exhibit differences in their functional activity, they function differently an example of this is a gene coding for a metabolic enzyme that can manifest in two forms these two different forms of the metabolic enzyme are respectively coded for by two different alleles one version of this metabolic enzyme functions better at a lower temperature the other version of this metabolic enzyme functions better at a higher temperature the heterozygote is a mixture of both enzymes, and therefore may be at an advantage, being able to function at a wider temperature range (being composed of both an enzyme that's optimal at a high temp and an enzyme that's optimal at a low one) therefore the heterozygote is more advantageous than either homozygote

incomplete penetrance

this is a phenomenon in which an allele that is expected to cause a particular phenotype (probably bc it is dominant) does not implement the expression of the phenotype it is coding for there is dominant trait known as polydactyly the condition of polydactyly causes additional fingers and/or toes this condition of polydactyly is due to an autosomal (therefore not sex linked, this allele is found in a gene located on an autosome) dominant allele a single copy of this allele is enough for the phenotypic trait of polydactyly to be expressed however there can be scenarios in which the individuals carry the dominant allele but they do not exhibit the trait look at notes for a pedigree of the polydactyly trait the dominant allele despite its presence in a heterozygous organism may not penetrate into the phenotype of the individual alternative for recessive traits incomplete penetrance is possible if there is a homozygous recessive organism and it does not express the recessive trait despite the present of the two recessive alleles the measure of penetrance of a trait is described at the population level if 60 percent of the heterozygotes carrying the dominant allele exhibit the trait coded for by the dominant allele, then the trait is considered 60 percent penetrant, as there is a percentage (40 percent) of heterozygotes that carry the dominant allele but do not express the phenotypic trait that the dominant allele codes for at an individual level, the trait is either there in the individual or not

sexual dimorphism

this is a phenomenon in which members of the opposite sex have present as morphologically different (you are able to distinguish members of opposite sexes due to the marked, documented differences in their morphologies) this phenomenon of the sexes in a species being distinct and markedly different is one common to many mammal species an example of sexual dimorphism is in bird, where male and female birds are markedly morphologically different: males have a lot of ornate plumage (peacocks) females have less ornate, more plain plumage sexual dimorphism in roosters: roosters (males) have a larger comb and wattles, longer neck and tail feathers hens (females) have a smaller comb and wattles, shorter neck and tails feathers these sex limited features are found in one sex of these organisms (rooster-male) but never in normal hens

genetic redundancy

this is a phenomenon that explains that one gene is able to compensate for the gene knockout/loss of another gene the causes of gene redundancy include the following: 1) gene duplication there are genes that due to evolution have been duplicated, so individuals may have two or more copies of similar genes that all code for similar things that do similar functions, therefore one gene is able to compensate for another similar gene these genes, bc they are not completely identical to one another (simply similar, different due to the accumulation and conglomeration of random changes that occurred during evolution) if one paralog is missing or knocked out, the other paralog can compensate for it 2) gene redundancy may involve proteins that both function similarly, both contribute to the same cellular function if one of the proteins is not there due to gene knockout, then the function of another protein (the production of that protein as well) may be increased, so that increased amount of a protein also contributed to that function can compensate for the protein that has been knocked out there will therefore not be a phenotypic change in the individual

sex-linked inheritance

this is a phenomenon where an allele is dominant in one sex but recessive in another (it is inherited dominantly, and is therefore more prevalent within one sex, and it is inherited recessively, and is therefore less prevalent within the other sex) sex influence is a phenomenon having to do with heterozygotes SEX INFLUENCED INHERITANCE IS MARKEDLY DISTINCT AND DIFFERENT FROM SEX-LINKED INHERITANCE the genes that govern sex-influenced traits are majority autosomal (found on non-sex chromosomes and therefore exhibiting an autosomal pattern of inheritance) they usually have nothing to do with either of the sex chromosomes and are not linked to X or Y an example of sex-linked inheritance is the common form of pattern baldness the balding pattern- this condition is described as hair loss on the front and top of the head, but not on the sides so the specificity of this condition, pattern baldness, is that the individual experiences hair loss on the front and top of the head, but not on the sides (that is how the condition is considered pattern baldness rather than full baldness, due to certain regions of the head not losing hair). this particular type of pattern baldness is inherited autosomally (it is an autosomal trait, found on non-sex chromosomes) if a male is heterozygous for the baldness allele, then he will become bald, it is inherited dominantly within the male sex if a female is heterozygous for the baldness allele, she will not present as bald if a female is homozygous for the baldness allele, then she will develop the trait of this particular kind of pattern baldness and present as partially bald however the difference is that this phenotypic expression of pattern baldness in a woman that is homozygous for the pattern baldness allele will usually be a significant thinning of the hair that occurs fairly late in the individual's life therefore the condition, even when women do phenotypically express it due to their allelic combination does not present to quite the degree it does in males, due to it being inherited recessively in females and dominantly in males this particular kind of pattern baldness is sex-influenced due to the influence of the male sex hormone testosterone the gene that codes for pattern baldness is one that normally codes for an enzyme known as 5-a-reductase 5-a-reductase the enzyme coded for by this pattern baldness one usually, converts testosterone to a 5-a-dihydrotestosterone (DHT) DHT, 5-a-dihydrotestosterone binds to cellular receptors and is able to affect the expression of a variety of genes, influence those genes and the phenotypic expression of the traits those genes are coding for it is able to affects the genes in scalp cells the allele that causes the phenotypic expression of pattern baldness is an over expression of the 5-a-reductase enzyme, which converts more testosterone than necessary to 5-a-dihydrotestosterone (DHT), which will then be able to exert more influence than normal on other genes, particular genes within scalp cells due to mature males on avg producing more testosterone than female, this allele, and the over expression of the 5-a-reductase enzyme has more of an impact in males (due to the overexpression ultimately affecting and converting testosterone) than in females, who usually have minimal amounts of this hormone in their body however, there is a possibility of a rare tumor of the adrenal gland this rare tumor in the adrenal gland can cause abnormally large, unexpected and unusual amounts of testosterone to be secreted in the female if a female has this condition of an unusually large amount of testosterone in her body, then she will inherit pattern baldness in a dominant manner, as males due therefore if she is heterozygous for pattern baldness, then will phenotypically express pattern baldness and present as bald however if the tumor is removed surgically, the amounts of testosterone in her body will lower to their regular minimal amounts, and therefore her body will no longer be quite as impacted by the 5-a-reductase enzyme and its conversion of testosterone to DHT, and the hair will return to its normal condition she will not present as phenotypically bald if she is heterozygous for this trait the autosomal nature of pattern baldness (the autosomal pattern of inheritance it follows) has been documented and revealed by human pedigrees in the human pedigree shown, a bald male can inherit the bald allele from either parent (due to it following an autosomal pattern of inheritance being an autosomal trait) therefore bald fathers are able to pass this trait to their sons this would not be able to occur (bald fathers would not be able to pass the trait of pattern baldness to their sons) if this trait was X-linked this is bc fathers are not able to pass an X chromosome to their sons, that X chromosome comes from their mothers therefore if a trait is X-linked, the only way males can inherit it is from their mother, bc the mother passes on one of her X chromosomes to their male offspring looking at a multitude of pedigrees, it has been determined that: bald fathers, on avg have at least 50% bald sons, 1/2 of their sons are bald (probably due to males having to be heterozygous or homozygous in order to inherit pattern baldness, therefore pattern baldness being far more common in males) if the bald fathers are homozygous for pattern baldness, then it is anticipated that they will produce even more bald male offspring proportionally (amongst their offspring, there will be a higher percentage of bald males) this above proportion of a higher percent of bald male offspring will also occur if the mother carries one or two copies of the bald allele Punnett square: there is a cross bw a heterozygous, affected, bald male and a heterozygous, unaffected, non bald female these parents will produce 75% bald male offspring these parents will produce 25% bald female offspring if there was the presence of a homozygous bald male or female in the pairing, then all bald sons would be produced in a cross bw two heterozygous individuals, the ratio of bald to nonbald offspring is 4:4, 1:1 ratio of bald sons: bald daughter is 3:1 ratio of nonbald sons to bald daughter is 1:1 ratio of bald sons to nonbald daughter is 1:1 ratio of nonbald sons to. nonbald daughter is 1:3

reciprocal cross

this is a second cross that occurs where the sexes and phenotypes (and therefore genotypes) are reversed in the reciprocal cross done bw golden retrievers, an affected female animal is crossed with an unaffected male therefore the female is homozygous dominant for DMD, while the male is completely unaffected this cross producers female carrier offsprings that are unaffected but carry the allele coding for DMD that makes the protein dystrophin nonfunctional, thereby resulting in important muscles being weakened (heart and lung muscles) the males are all affected by DMD, due to the hemizygous allelic combination, and the only allele influencing whether or not they have DMD is located on the X chromosome, of which they only have one from the completely affected an important thing to remember with x-linked genes and crosses bw males and females is that: -the male cannot transmit the X chromosome to his sons, so even if he is a carrier, it will not pass onto the son from him bc he is contributing the Y chromosome that does not connect at all with the X-linked gene and condition we are observing -the female transmits an X chromosome always to both female and male offspring this helps us to understand why X-linked traits do not behave equally in reciprocal crosses bc of the unique properties of said traits the observation that reciprocal crosses (crosses where you simply switch the genders and corresponding phenotypes) does not yield the same results can indicate that a trait is indeed x-linked

suppressor mutation

this is a second mutation that reverses the effects of a first mutation when a suppressor mutation is found in a different gene than the first mutation, it is designated as an INTERGENIC OR EXTRAGENIC SUPPRESSOR why do researchers isolate and analyze suppressor mutations? the primary goal of isolation of suppressor mutations is to identify common proteins with similar functions that participate in a common cellular process (common to them both) this cellular process they both participate in leads to the manipulation of the phenotypic expression of a trait an example of this is in Drosophila melanogastor, there are several proteins of this organism that all function in a signaling pathway this signaling pathway they are all participatory in determines which parts of the flies body contain/are made up of sensory cells an area of a flies body rife with sensory cells is the area designated for the mechanosensory bristles of flies- you will find many sensory cells here, and recall that there are several proteins all involved in a pathway that determines that this portion of the body, the mechanosensory bristles, contain sensory cells researchers have been able to isolate dominant mutants/mutations that result in flies having fewer mechanosensory bristles the mutated gene coding for fewer mechanosensory bristles is known as Hairless the wild-type more common allele is h, coding for a normal number of mechanosensory bristles the dominant mutant (a mutation inherited dominantly) is H, this allele codes for flies with fewer bristles once researchers found the Hairless mutant, the isolated other mutants that were able to successfully suppress the hairless phenotype that the Hairless mutant coded for (the H allele codes for hairlessness) these suppressor mutations suppressed the phenotypic expression of a mutant trait coded for by the Hairless mutant, and ensured that the flies had a normal number of mechanosensory bristles these suppressor mutants are also dominant (inherited dominantly) and are found in a gene designated Suppressor of Hairless the wild type allele is designated as soh, and this soh allele codes for the SoH protein, the protein that prevents the formation of sensory structure, stops the growth of mechanosensory bristles the dominant mutant allele is designated as SoH, and this is the allele that combats the H allele coding for hairlessness, and ensures that flies have the appropriate number of mechanosensory bristles explaining these mutations at a molecular level: the functions of the proteins coded for by the wild type genes, h and soh soh codes for the SoH protein, it prevents the formation of sensory structures such as bristles (mechanosensory bristles in Drosophila melanogaster) in areas where they should not be the Hairless protein is formed in areas of the body where the mechanosensory bristles should form, and fights the SoH protein by binding to it and stopping its functionality, which is to code for hairlessness and restrict the amount of hair grown in particular regions the Hairless protein that suppresses the SoH protein will be coded for by the hh homozygote (the wild type allele, as hh should be coding for a normal number of mechanosensory bristles on a fly), and bristles will form in areas where you find the Hairless protein coded for by the hh homozygote allelic combination what if there was a single mutation in the Hairless gene? there is a heterozygote carrying the dominant allele H (which codes for hairlessness) therefore only half of the functional Hairless protein (which codes for the production of mechanosensory bristles) will be produced in this heterozygote the SoH proteins that are made can not be completely inhibited (the SoH proteins preventing hair growth in particular regions can not be properly suppressed due to the lack of the hh allelic combination coding for a properly functioning Hair Suppressor gene that stimulates mechanosensory bristle growth) therefore the SoH genes are uninhibited, mechanosensory bristles are not formed, and the fly is hairless what happens in a double mutant? the suppressor mutation eliminates one of the two functional soh alleles coding for hair limitation therefore the double mutant is expressing one function h allele coding for hair growth and one functional soh allele coding for hair loss that it is fighting it is a fair fight, and the SoH protein is substantially inhibited in this heterozygote, mechanosensory bristles are formed mutant and its suppressor analysis: sometimes the two proteins simply physically mechanically interact with one another, such as with the Hairless and SoH proteins proteins encoded by individual and different genes can both participate in the same function, but do not physically/mechanically interact with one another (they can be in a pathway) an example of the above is in a pathway, there could be a mutation that greatly decreases the amount of one enzyme though this enzyme doesn't interact with any other enzymes, it is part of a pathway, and lack of the proper amount of this enzyme may prevent the following enzymes from functioning and the proper product of the biochemical pathway if the product of the affected biochemical pathway is usually an amino acid, the individual with the mutation would need to be supplied the amino acid a suppressor mutation can also by preventing a previous mutation, increase the function of a different enzyme that participates in the pathway, and ensure that the organism can make the proper amount of the correct amino acid the individual would then no longer need to be supplied the amino acid other suppressors impact phenotypic expression by altering the amount of protein coded for by another mutant gene an example of this is that a mutation may decrease the functionality of a protein that is important in implementing sugar metabolism the organism with this mutation is unable to metabolize sugar the suppressor mutation in a different gene could alter genetic regulatory proteins (that up regulate or down regulate genes) and cause the mutant gene to produce more of the protein, so despite the decreased functionality, there is more of the protein to compensate for that, and metabolize an adequate amount of sugar there would be a faster and adequate rate of sugar metabolism

self-fertilization

this is a situation of fertilization in which the pollen and the egg are derived from the same plant, so the two haploid gametes that join to form a diploid zygote come from the same plant why does self fertilization occur- apparently in peas, there is the KEEL- A MODIFIED PETAL THAT COVERS THE REPRODUCTIVE STRUCTURES OF THE PLANT- hiding these reproductive structures from view therefore plants usually naturally reproduce due to self fertilization apparently the pollination/fertilization occurs before the flower blooms/opens this posed an issue however bc Mendel wanted to conduct hybrid fertilization experiments, where he would take two markedly different pea plants and breed them with one another how would he do that if the natural instinct of pea plants is self fertilization? apparently pea plants have relatively large flowers that are very easy to manipulate therefore Mendel was able to cross two different plants and have one fertilize the other this process of crossing one markedly distinct plant with another is called cross-fertilization it requires that the pollen from one distinct plant be manually place on the stigma of the plant that is getting fertilized Mendel pried open immature flowers (flowers that had not yet bloomed or opened up) and he removed the anthers containing the pollen grain containing the sperm so that sperm of that plant would not be produced this rendered the plant incapable of self-fertilization he would then take pollen from a different plant, touching its mature anthers (containing the pollen grains full of sperm) with a paintbrush in order to collect the sperm cells he then took that paintbrush covered with the plant's sperm cells, and applied this to the stigma of the flower plant that had had its anthers removed (so it could not self fertilize, opening itself up to the possibility of being fertilized by pollen from another plant)

overdominance

this is a situation where the heterozygote possess a trait that is more beneficial than the trait expressed by the homozygous dominant individual and the trait expressed by the homozygous recessive individual Molecular: there are 3 common ways in which heterozygote individuals benefit more than either homozygote: 1) the cells of the homozygote may have increased infection resistance (they resist infection by microorganisms more than the cells of either homozygote) 2) these heterozygote cells may produce more forms of proteins dimers (2 piece proteins) that have enhanced function, better functionality and characteristics than the proteins of either homozygote 3) these heterozygote cells may produce proteins that function under a multitude of conditions (these proteins are not limited by many factors, something that the proteins of either homozygote may be limited by in regards to functionality)

chi square test

this is a statistical method used to determine goodness of fit, how well the observed and expected data match up with one another the chi square test is utilized in order to analyze population data, where members of a population fall into diff categories (perhaps categories of variants of a character)

mitotic spindle apparatus

this is a structure that both develops, functions, and disappears during the mitotic phase of the cell cycle THE MITOTIC SPINDLE APPARATUS is also known as the MITOTIC SPINDLE the mitotic spindle's function focuses on the organization and the separation of chromosomes from one another, their assortment into two genetically identical daughter cells, the mitotic spindle is integral in the process of evenly dividing the genetic material

dosage compensation

this is a type of epigenetic inheritance that is able to offset and correct alterations in the number of sex chromosomes one of the sex chromosomes is altered, changed so that males and females both within their sex chromosomes (their allosomes) and their autosomes have similar levels and amounts of gene expression (due to the fact that the sex chromosome pair in the 23rd pair of chromosomes can be a prominent location where differences in gene expression levels- where females could potentially have more gene expression than males due to having 2 X chromosomes with over a thousand genes and males having 1 X chromosome with over a thousand genes and then a Y chromosome with around 80 genes- can occur) males and females do not have the same pairing/complement of sex chromosomes, and therefore there is the potential that they are substantially different in regards to their respective amounts of gene expression in mammals, dosage compensation usually occurs during the early initial stages of embryonic development dosage compensation is a phenomenon detailing the fact that the level of expression of many genes on the sex chromosomes is similar in both of the sexes (the amounts of gene expression on the sex chromosomes is similar in both sexes) despite males and females having different combinations of sex chromosomes (XY and XX) the term dosage compensation was coined by Hermann Muller he coined this term in order to explain the effects of eye color mutations in Drosophila in Hermann Muller's experimentation, he observed that female flies that were homozygous for certain X-linked eye color color alleles (so the gene for eye color was found on the sex chromosomes, particularly the X chromosome) had a similar phenotype to males that were hemizygous for the same character in females having the homozygous allelic combination (the allele coding for apricot eye color on both X chromosomes) and males having the hemizygous allelic combination (having the allele for apricot eye color on their one X chromosome, and nothing to combat or align with this allele on the Y chromosome as this is an X-linked gene), they both had the same apricot eye color however, in females with one copy of the apricot allele and on the other X chromosome, a deletion of the gene and therefore no presence of a second allele coding for any sort of eye color, there was the phenotypic expression of a paler eye color therefore it was determined that one copy of a specific allele (the one coding for the apricot eye color) in the female fly is not equivalent to one specific allele in the male coding for the apricot eye color, these alleles despite being the same and being present in the same number in both males and females, do not result in the expression of the same phenotypic trait in the males and females two copies of the allele coding for apricot eye color in the female are equivalent to one copy of the allele coding for apricot eye color in the male, these two different allelic combinations both result in the same phenotypic expression of the apricot eyes there is a difference in gene dosage within males and females that results in the same phenotypic expression is being compensated for at the level of the expression of these different allelic combinations, so they result in the same phenotypic expression despite the difference in the gene dosage at the level of allelic combination/gene expression, there is an evening out that occurs in order to result in the two different allelic combinations expressing the same phenotypic trait

true-breeding line/strain

this is a variety of an organism that continues to produce the same trait after multiple instances of self-fertilization and multiple offspring generations all presenting the same morphologically in regards to a particular characteristic

lethal alleles

this is an allele that has the potential to cause the death of an organism an organism can die from the presence of a lethal allele in its allelic combinations Molecular: these are the most common loss-of-function allele, the presence of this lethal allele means that the gene loses its functions, and the proteins necessary for survival are not coded for due to the presence of this mutated allele in other cases, the lethal allegation can be present due to a mutation within a nonessential gene (so the mutation within that gene doesn't directly affect the health of the organism) this mutation within a nonessential gene leads to a protein functioning with abnormal and detrimental consequences

epigenetic inheritance

this is an inheritance pattern where there is a modification that occurs to a nuclear gene or an entire chromosome (nuclear gene would be a gene found within the nucleus, probably on a chromosome in a eukaryote or in the circular DNA of a prokaryote, and of course chromosomes are located within the nucleus, so epigenetic inheritance has to do with the genetic material within the nucleus) this modification to a nuclear gene or chromosome causes a change in gene expression, but will not have any lasting capabilities, and will not be consistent across generations epigenetic inheritance patterns are due to the DNA and chromosomal alterations/mutations that can occur during -oogenesis (oocyte/egg formation) - spermatogenesis (sperm formation) - early stages of embryogenesis (the sperm and the egg coming together in order to form an embryo, during this process of the two haploid gamete cells combining with one another, there is still a possibility of mutations and alterations of genes and chromosomes, and there remains this possibility when the created embryonic cell is replicating) when epigenetic changes (mutations and/or alterations to genes and chromosomes during oogenesis, spermatogenesis, or embryonic development) are initiated during any one of these processes, they alter the expression of genes in a way that can be somewhat reversed and corrected during the individual's lifetime epigenetic changes can permanently affect the phenotypic expression of an individual during their individual lifetime HOWEVER epigenetic changes/modifications/alterations (mutations/alterations occurring to specific genes or entire chromosomes or portions of chromosomes) are not permanent over the course of a multitude of succeeding generations, and these epigenetic changes do not alter the DNA sequence itself an example to further explain this concept: there may be an epigenetic change that inactivates a particular gene, and it is never expressed/activated during the lifetime of the individual with this gene mutation (THAT DOES NOT ALTER THE DNA sequence AS EPIGENETIC SEQUENCES DO NOT ALTER THE DNA sequence ITSELF, and in this particular situation, the gene is simply inactivated and not allowed to express itself) 'so during the course of this individual's lifetime, this gene remains inactive, and is not expressed however, during gametogenesis in this individual, the gametes may have the active version of this gene (this gene will be activated within these gametes), and this gene will be expressed and produce whatever phenotypic trait it codes for during the lifetime of an offspring created with a gamete with the activate gene therefore the offspring will have the activated gene, due to the gamete of their parent having the activated gene, while the parent will still have the inactivated form of the gene

imprinting and genomic imprinting

this is another phenomenon found within epigenetics imprinting is a marking process that has a memory an example of genomic imprinting is an example having to do with newly hatched/born birds so these birds are newly born, newly hatched, and these newly born bird recognize marks on their parents, and allows these newly born birds to recognize and distinguish their parents from other birds, to the marks on their parents that they can recognize genomic imprinting specifically has to due with a situation analogous to the one described above (where newly born birds are able to recognize their parents and distinguish them from other birds to the marking on their parents) genomic imprinting is a scenario in which there is segment of DNA that is marked and therefore distinguished this mark on this particular segment of DNA is maintained, retained, and recognized throughout the entire lifetime of the organism that contains this DNA with this marked segment the phenotypes that are coded for by imprinted genes follow a pattern of inheritance starkly different from classic Mendelian patterns of inheritance this is because due to the segment of DNA being marked, this allows the offspring with this marked DNA to distinguish bw the alleles that they have inherited from their mother and the alleles that they have inherited from their father in their ability to distinguish the allele for a gene they've inherited from their mother, and the allele for the same gene they've inherited from their father, they will express only one of these alleles this aforementioned process is known as monoallelic expression, where only one inherited allele for a gene is expressed

sex-limited inheritance

this is another phenomenon that influences an organism's phenotypic expression this is where a trait simply occurs in only one of the two sexes one of the sexes shows this trait, the other doesn't the genes that influence sex-limited traits (the phenotypic expression of those traits) can be autosomal (located on homologous pairs of non-sex chromosomes) or X-linked (located on homologs pairs of X chromosomes in females and the one X chromosome in males) examples of sex-limited traits: -ovary production, ovaries are only created in females -testes production, testes are only created in males therefore females are only able to produce eggs as their haploid gametes, and males are only able to produce sperm as their haploid gametes

X chromosomal controlling (Xce)

this is another region on x chromosomes that influences X-inactivation genetic variation is something that occurs in the X chromosomal controlling element (Xce) region An X chromosome that carries a strong Xce is more likely to remain active rather than an X chromosome that carries a weak Xce so if an X chromosome has a strong x chromosomal controlling element region, then it will be activated if an X chromosome has a weak x chromosomal controlling element region, then this X chromosome will be inactivated (with this X chromosome with a weak x chromosomal controlling element region, this nonrandom and skewed X inactivation will occur in this chromosome) it is not fully understood how x chromosomal controlling element regions influence x-inactivation however, some researchers speculate that the x chromosomal controlling element region operates as a site where proteins bind and regulate the expression of genes such as the Xist or Tsix gene in the Xic region of the chromosome, therefore influencing inactivation or activation genetic variation that occurs in the x chromosomal controlling element region can enhance Xist expression, and this genetic variation that enhances the expression of this gene coding for an inactivated X chromosome would tend to influence the implementation of compaction on the X chromosome, and cause it to become a Barr body if there was genetic variation that enhanced the expression of the Tsix gene, then there would would be the prevention of X inactivation due to the expression of the gene that codes for the prevention of x inactivation

expressivity

this is another term that is used to properly describe the outcome of a trait specifically, this term indicates the degree to which a trait is expressed an example of a trait and expressivity of this trait is polydactyly the number of extra digits (and whether those are fingers and/or toes) can vary from individual to individual, depending on the expressivity of the polydactyly trait in one individual, they may only have an extra toe on only one foot another individual with polydactyly may have more expressivity of this trait, where they have extra digits on the hands as well as the feet high expressivity of polydactyly is where an individual has several extra digits low expressivity of polydactyly would be where the individual has a single extra digit

asexual reproduction

this is one of the processes involved in copying and transmitting chromosomes through the process of cell division ASEXUAL REPRODUCTION in the process of asexual reproduction, there are these steps that occur: A PREEXISTING CELL DIVIDES IN ORDER TO PRODUCE TWO NEW CELLS there is a preexisting cell, and this preexisting cell divides in order to produce two new cells identical to the first by convention, the original cell from which two new cells are made (due to the original cell dividing into these two new cells) is designated as the MOTHER CELL the two new cells that result from the division of the original/mother cell are designated as the DAUGHTER CELLS, as they descended from the mother cell, the division of the mother cell into the two daughter cells when we are looking at a unicellular species that undergoes asexual reproduction, this is how we designate the various entities involved in this process: the mother cell is considered to be one entity, one distinct individual the two daughter cells are also considered to be separate and distinct entities, two distinct individuals, they are considered two new separate organisms that have developed from the division of the mother cell asexual reproduction is the process by which bacterial cells (which fall under the category of prokaryotic cells) proliferate the way that bacterial cells replicate is through asexual reproduction asexual reproduction can also occur within eukaryotes specifically PARTICULAR UNICELLULAR EUKARYOTES these particular unicellular eukaryotes that are capable of undergoing asexual reproduction are THE AMOEBA AND BAKER'S YEAST the amoeba and baker's yeast are capable of undergoing asexual reproduction the scientific terminology for baker's yeast is SACCHAROMYCES CEREVISIAE

random sampling error

this is the deviation bw the observed and expected outcomes, bc these outcomes are random and not guaranteed there is a certain likelihood that an event will occur along with the established rates of probability however, again depending on the sample size, the number of times an event is repeated, you might find your experiment slightly or dramatically deviating from the established results you would expect to occur this is due to the randomness, and the deviation between the observed outcomes and the expected outcomes is recognized as the random sampling error within a small sample, one would expect the random sampling error to be quite larger within a large sample, due to the repetition of the event, one would expect the random sampling error to be much smaller

genetic cross

this is the fundamental and main approach of a transmission geneticist a genetic cross involving breeding two individuals, then analyzing their offspring in order to understand how traits are passed from those selected parents to their offspring with experimental organisms (more variables at stake and possibilities) the researcher selects two parents with particular traits, then categorizes the offspring according to the traits that they have (The offspring produced by the selected parents) this process of categorizing the offspring of selected parents is quantitative in nature an example of this process is an experimenter (a transmission geneticist) taking two tall pea plants and crossing them, then obtaining 100 offspring that fall into the 2 categories of 75 tall and 25 dwarf

DNA methylation

this is the process by which a methyl group CH3 is attached onto a cytosine base of DNA the process of DNA methylation is one that manipulates the way in which eukaryotic genes are regulated, DNA methylation regulates the expression and degree of expression of eukaryotic genes research done on the process of genomic imprinting has concluded that there is an IMPRINTING CONTROL REGION- ICR, that is located near the imprinted/marked gene, the one that is selected to either be expressed or not expressed a portion of the DNA within the IMPRINTING CONTROL REGION is known as the DIFFERENTIALLY METHYLATED DOMAIN- DMD so within the region near the imprinted gene, the imprinting control region, there is a portion of DNA within the imprinting control region known as the differentially methylated domain so to recall, there is a region of DNA called the IMPRINTING CONTROL REGION that is located near the imprinted/marked gene (that is probably marked for expression and being transcriptionally active) within the IMPRINTING CONTROL REGION located near the imprinted gene, there is the differentially methylated domain also known as DMD depending on the gene we are looking at, the DIFFERENTIALLY METHYLATED DOMAIN IS METHYLATED EITHER IN THE EGG OR THE SPERM, but not both of the haploid gametes that come together in order to form the zygote THE IMPRINTING CONTROL REGION also contains binding sites for one or more than one protein, that are responsible for and influence the transcription and expression of the selected imprinted/marked genes so within the imprinting control region that is located near the imprinted gene, there are sites for one or more proteins that influence the expression and transcription of that specific imprinted gene to bind and thus implement their function of influencing the expression and transcription of that particular selected/imprinted gene for the majority of imprinted genes, the process of methylation (the addition of a methyl group to a cytosine nitrogenous base in DNA), causes that area of the DNA that is methylated to not be transcriptionally active, thus stopping gene expression methylation can work in two ways: 1) it can enhance the binding of proteins that are responsible for stopping transcription of a gene, so it helps proteins that inhibit the transcription of DNA to bind to a particular region or gene that will help them to do their function of making that particular gene transcriptionally inactive 2) it can also inhibit the binding of proteins that help the process of transcription along, so if there are any proteins that assist in the process of genes being expressed, then DNA methylation will function in the way that it will stop those transcription-enhancing proteins from being able to bind, and therefore the genes they would assist in being expressed are not assisted, therefore not transcriptionally active, and therefore will not be expressed IMPRINTING- this phenomenon/implemented process is usually described as a marking/selecting process that prevents transcription of a particular gene, a particular part of a chromosome, the entirety of a chromosome, or a set of chromosomes, and therefore makes the gene itself or a collection of genes (depending on what specific genetic material is marked) transcriptionally inactive, and therefore a gene or a collection of genes cannot and are not expressed however, the aforementioned is not always the case, genes or a multitude of genes are not always marked to be transcriptionally inactive if you look at two imprinted human genes: H19 and Igf2, these are two very interesting examples of two imprinted human genes, genes that undergo genomic imprinting these two genes, H19 and Igf2 are fairly close to one another in regards to positionally on human chromosome 11 both of these genes, H19 and Igf2 appear to be controlled by the same IMPRINTING CONTROL REGION the IMPRINTING CONTROL REGION they both seem to be controlled by is a region composed of 52,000 base pairs, and this imprinting control region is as expected, near both genes, lying right in b/w the H19 and Igf2 genes this imprinting control region is highly methylated (the attachment of a methyl group to a cytosine nitrogenous base) on the homolog of chromosome 11 that is inherited paternally, but this region is not at all methylated on the homolog of chromosome 11 that is maternally inherited on the maternally inherited chromosome, where the imprinting control region lying b/w the H19 and Igf2 genes is not methylated at all, there is a protein called CTC-binding factor that is able to bind to the imprinting control region so when the imprinting control region (as on the maternally inherited chromosome 11) is not methylated, there is a protein known as the CTC-binding factor that is able to bind to this region the CTC-binding factor protein is designated as such due to the fact that the CTC-binding factor binds to a region of DNA in the imprinting control region that is rich in CYTOSINE-THYMINE-CYTOSINE SEQUENCES (otherwise known as CTC sequences) so the CTC binding factor protein is known as such because in the imprinting control region, it binds to the region most abundant in CTC sequences, sequences of cytosine-thymine-cytosine the imprinting control region contains several regions that are rich in CTC when the imprinting control region is not methylated (and therefore the CTC sequences within this imprinting control region are also not methylated) the CTC binding factor protein is able to bind to the regions of the imprinting control region rich in unmethylated CTCs there are two effects: 1) the process of the CTC binding factor proteins binding to regions of the imprinting control region rich in CTC sequences prevents the binding of activator proteins to the Igf2 gene (proteins that would activate the expression of Igf2 gene and make the DNA region encoding the Igf2 gene transcriptionally active) therefore the Igf2 gene is not able to be transcriptionally active due to the prevention of binding of the activator proteins that would assist in the transcriptional activation and expression of the Igf2 gene the fact that the Igf2 gene is no longer transcriptionally active (due to the binding of the CTC binding factor proteins to regions of the imprinting control region rich in CTC sequences and subsequent prevention of Igf2 gene activators binding to the Igf2 gene) means that the activator proteins for the H19 gene are able to bind, and the H19 gene is expressed the above is all due to methylation not taking place how does the process of methylation affect whether or not the Igf2 and H19 genes are transcriptionally active? when cytosines within the imprinting control region located right in b/w the Igf2 and H19 genes are methylated (a methyl group is attached to these cytosine nitrogenous base pairs), the CTC-binding factor protein that bind to regions of the imprinting control region rich in CTC sequences is unable to bind to these sequences, as the cytosines of these sequences have methyl groups attached to them and have now undergone methylation and are transcriptionally inactive due to the inability of the CTC binding factor proteins to bind to the imprinting control region, the activator proteins are not prevented from binding, are able to bind, and the Igf2 gene is transcriptionally active and is expressed the DNA methylation, resulting in the Igf2 gene being transcriptionally active and expressed, also results in the H19 gene not being transcriptionally active, and therefore not being expressed

two-factor crosses/dihybrid crosses

this is where the experimenter looks at the inheritance of two different characters (two different traits) within the same groups of individuals an example of this would be where: -one character is seed shape with the variants round and wrinkled -the other character is seed color with the variants yellow and green Mendel followed both characters throughout generations one possibility in a dihybrid cross is that the genetics determinants for the two characters you are following are linked, and therefore these genetic determinants of these two characters are always inherited in certain combinations as a unit therefore the only allelic combinations in a factor cross would be RY and ry, where these two alleles are inherited as a unit the other possibility is that the genetic determinants of these characters are not linked, and these genetic determinants assort themselves independently into haploid gametes therefore the possible allelic combinations of the gametes are RY, Ry, rY, and ry we need to recall that the gametes can only contain one allele for a particular gene In Mendel's two factor cross, he started with two different strains of true breeding plants these two distinct true breeding plants differed in regards to seed shape and seed color one of the true breeding plants had round and yellow seeds the other true breeding plant had wrinkled and green seeds the seeds created by the crossing of these true breeding plants (containing the plant embryo) were designated as part of the first filial generation the F1 seeds displayed the phenotype of round and yellow seeds within the F2 generation and its results, the independent assortment model for genetic determinants is supported when Mendel crossed the F1 generation with itself (self-fertilization), he was breeding two heterozygous parents (heterozygous for both characters/traits) therefore the possible gamete combinations and the possible zygote allelic combinations became numerous be sure to review this chart detailing the possibilities as Mendel went from the first filial generation to the second filial generation within the F2 generation, there were seeds that were round and green, and seeds that were wrinkled and yellow these categories of traits (these combinations of the variants of the characters) are designated as nonparentals bc these combinations of traits were not found in the true breeding plants of the parental generation these combinations do not match combinations seen in the parental generation this occurrence contradicts the linkage model, concluding that these characters are not linked, due to the possibility of new combinations as you move from generation to generation, combinations that do not match the combinations found in the parental generation (leading to the conclusion that the genetic determinants of these characters and all traits undergo independent assortment during gamete formation)

incomplete penetrance

this patten occurs when the dominant phenotype (the dominant trait) is not expressed even when the individual carries the dominant allele (such as in a heterozygous organism) an example of the above is where an individual is heterozygous and carries the dominant polydactyl allele, but presents with a normal number of fingers and toes, bc the presence of that dominant allele is not enough for the penetrance of the dominant polydactyl trait (probably two recessive alleles are required) Molecular: the presence of a dominant gene does not necessarily mean that the protein coded for by the gene will function and exert its effects the reasons why a protein coded for by the dominant allele may not exert its effects are: - environmental influences - the presence of other genes being expressed, and these genes may encode proteins that counteract the effects and functionality of the protein the other gene is coding for, so this gene is rendered ineffective due to the presence of another gene coding for a protein that makes the protein of the former gene obsolete and unable to function and result in the expression of the phenotypic trait the dominant allele is coding for

sex-influenced inheritance

this pattern of inheritance involves how the sex of the individual may influence the expression of the phenotype some alleles are recessive in one sex, and dominant in the other an example of the above- sex influenced inheritance is male pattern baldness, where pattern baldness is more common in males than females, the allele presents as dominant in males (where a hemizygous allelic combination will suffice to cause male pattern baldness) and recessive in females (where due to the presence of two X chromosomes in the female, there has to be an allelic combination with two recessive alleles in order for pattern baldness to present itself in the female) Molecular: sex hormones can regulate and influence the molecular expression of genes, how much of the protein they code for this control of the molecular expression of genes influences the ways in which the alleles of those genes influence the phenotype of the individual, and what phenotypic traits will present

Lyon hypothesis

this phenomenon is also designated as the mechanism of X-inactivation this phenomenon is showed by a schematic illustration within the book: a white and black variegated coat color (so patches of black and white on coats of organisms, a coat that varies in regards to those patches and their conformation from organism to organism) within particular strains of mice so particular strains of mice have these patches of black and white on their coats a female mouse is shown this female mouse inherited an X chromosome from its mother this X chromosome carries an allele that codes for the phenotypic coat trait of a white coat color the allele that codes for a white coat color is X^b the X chromosome that this female mouse inherited from its father is one that carries an allele that codes for a black coat color the allele that codes for a black coat color is X^B x-inactivation occurs within this organism, but how? why does this animal, having one allele coding for a white coat color, and one allele coding for a black coat color, the first inherited from the mother, and the second inherited from the father, have a variegated, patchy coat pattern of black and white initially, within this organism, both of the X chromosomes and therefore both of the alleles and the entire gene coding for coat color are active however, during embryonic development of the female mouse with the sex chromosomal combination of xx, one of the two X chromosomes in every somatic cell that is created is randomly inactivated, and becomes a Barr body, and this is left up to chance which chromosome that is (and this occurs in the vein of dosage compensation to ensure that the male and female mice produce the same amount of gene product) within one embryonic somatic cell, the X^B chromosome can be inactivated, the allele coding for the black coat color is inactivated, and therefore within that particular embryonic somatic cell, the allele coding for white coat color X^b will be still active, and that cell will replicate to make more cells with that same inactivation of the allele coding for black coat color, resulting in a bunch of cells around the body producing proteins that make white pigment when the embryo cell with the inactivated XB allele coding for the black coat color continues to mature and undergo mitosis, the embryonic cell will divide, and eventually end with billions of cells composing the mouse organism the epithelial cells of this organism (stemming from that original embryonic cell) will all have the XB allele inactivated, and therefore will produce the physiological phenotype of white pigment and the phenotypic expression of white fur however there can and probably will be another embryonic cell present during the early stages of embryonic development, that will have the Xb allele coding for white fur inactive, and will replicate into billions of cells composing the adult mouse, which results in all of the epithelial cells produced from that original embryonic cell all having the allele Xb coding for white fur inactive, and having the allele XB coding for black fur completely active, thus producing the physiological trait of black pigment and the morphological trait of black fur this will result in a collection of cells with the allele on their X chromosome coding for coat color coding for a black coat color, and another collection of cells with the allele on their X chromosome coding for coat color coding for a white coat color and these collections are split into smaller collections in a pattern along the coat of the organism therefore the organism has patches of white fur and patches of dark fur, fur composed of epithelial cells with the allele coding for white fur color and fur. composed of epithelial cells with the allele coding for black fur color

why are so many defective mutant alleles inherited in a recessive manner?

this question can be approached quantitatively by observing protein function diploid individuals have two copies of every gene (except sex-linked genes, due to their being one copy when it comes to an x-linked or y-linked gene within the opposite sex due to the breakdown of the fact that females have two X chromosomes- therefore two alleles for an x-linked trait and none for a y-linked trait and males have one X chromosome and one Y chromosome- therefore one alleles for an x-linked trait and one allele for a y-linked trait) if there is a simple dominant-recessive relationship, then the presence of a recessive allele within a heterozygous individual does affect the phenotypic expression of a trait, it is overwhelmed by the presence of the dominant allele coding for the dominant phenotypic trait that the heterozygote will express a single copy of the dominant allele is enough to mask the effects (if there are any) of the recessive allele the recessive allele cannot produce a functional protein, which begs the question, how do we explain the heterozygote having a wild-type phenotype? the common explanation is that 50 percent of the functional protein provided by the dominant allele of the allelic combination of the heterozygote is enough to cause the wild type phenotype this allele is coding for to be expressed in the example with flowers, PP (purple), Pp (purple), and pp (white), the PP homozygous dominant flower with its two dominant alleles is producing twice as much of the protein it requires in order for the phenotypic trait of purple to be expressed therefore is the amount of protein, as within the heterozygous Pp plant is reduced to 50 percent, that is exactly how much protein the plant needs in order for the purple flower trait to be expressed a second explanation for other genes and why a heterozygote expresses the dominant trait is the following: the heterozygote despite having 1 dominant and 1 recessive allele, produces more than 50 percent of the functional protein due to gene regulation the expression of the normal gene/the dominant allele may be increased/upregulated in the heterozygote with the heterozygous allelic combination in order to compensate for the lack of function found with the recessive allele in this allelic combination

product rule

this rule can be utilized in order to predict the probability of independent events (events that are not mutually exclusive) we can utilize probability in order to make predictions regarding the probability/likelihood of 2 or more independent outcomes independent- means that the occurrence of one event does does exclude the occurrence of the other, or affect it in any way an example is congenital analgesia- this is a rare, recessive human trait people with congenital analgesia are able to distinguish sharp and dull, and hot and cold as distinct, but they are not able to perceive the extremes of these sensations (extremely sharp, extremely hot, extremely cold) as painful first case of congenial analgesia- 1932- a man was a human pincushion, unable to feel pain at all look at notes for example the product rule can also be used in order to predict the outcome of a cross involving two or more genes look at notes for example

Mendelian inheritance

this term describes inheritance patterns that align with and obey the two laws established by Mendel's experimentation: the law of independent assortment and the law of segregation simple mendelian inheritance- a slightly tweaked take on mendelian inheritance (rather a subset category falling under mendelian inheritance) that sticks to the idea that traits, all characters are affected by a single gene with two different alleles (these two alleles coding for two different variants of the trait) and in these cases of a gene with two alleles coding for a trait, one allele is dominant over the other the ratios seen in these cases support Mendel's established laws an example of the situations obeying Mendelian laws is when two different true-breeding pea plants are crossed (this is known as a single factor cross, where the two organisms differ in a single factor/character and are pure breeding for this factor), and the resulting F1 generation is allowed to self-fertilize (monohybrid cross- a heterozygote fertilizing itself) the result of this self fertilization by the F1 generation results in an F2 generation showing the ratio of 3:1 in regards to tall:dwarf offspring

sex-linked gene

this term designates a gene that is found on one of the two types of sex chromosomes (X or Y), but not on both of them (bc then the gene would act like any gene coded on by an autosomal chromosome) there are hundreds of x-linked genes that have been identified in humans and other mammals the inheritance pattern of X-linked genes shows particular distinctive features males transmit X-linked genes only to their daughters, bc that is to who they can contribute their X chromosome to, as they can only contribute their Y chromosome to their male offspring sons receive x-linked genes from their mothers, as fathers cannot contribute their X chromosome to their sons when a male inherits a sex-linked gene that is specifically x-linked, they are homozygous for that gene due to the aforementioned properties of x-linked genes, males are more likely than females to be affected by rare, recessive X-linked disorders the transmission of sex-linked genes is dependent upon the sex of the parents and the offspring (bc the trait, unless it is pseudoautosomal) is always coded for on one specific type of chromosome, either X or Y and that dramatically affects patterns of inheritance due to the difference of probabilities in having male or female offspring with the condition, as well as the specific allelic combinations of the parents and how that will contribute to the allelic combinations of the offspring based on what kind of sex-linked gene we are looking at

pseudoautosomal inheritance

this term designates that the inheritance pattern of a gene is the same as the inheritance pattern of a gene on an autosome despite the presence of this gene being on one of the sex chromosomes (despite being technically sex-linked, it does not present as such in inheritance) similar to autosomal inheritance, in a pseudoautosomal inheritance pattern, males have two copies of pseudautosomally inherited genes (as pseudoautosomal genes are inherited in the exact same way as autosomal genes, as if the gene is coded for by two homologous chromosomes rather than one of the sex chromosomes) therefore, males are able to transmit these genes found on both of their sex chromosomes to their daughters and sons

simple mendelian inheritance

this term is commonly applied to the inheritance of alleles that aligns itself with Mendelian genetics one allele is dominant over the other (the other allele is recessive) however, some genes can have 3 or more alleles, which makes the situation more complicated in determining which alleles are dominant and which ones are recessive, and if that relationship changes as we compare various alleles Molecular points to note: 50 percent of the protein, produced by a single copy of the dominant allele (so if there is a heterozygote, with one dominant allele and one recessive allele), if 50 percent of the required protein is being produced by the single copy of the dominant allele, that is enough to produce the dominant trait the dominant allele is coding for

norm of reaction

this term refers to the effects of environmental variation on phenotypic expression of a trait the geneticists want to examine the phenotypic range seen in individuals with a specific genotype, to see how environment can impact the phenotypic expression despite the genotype being identical when geneticists are considered the environmental effect on the phenotypic expression of a trait, they look at a range of environmental conditions and their effects, rather than just two markedly different environmental conditions in order to evaluation the norm of reaction, the environmental variation found in the phenotypic expression of a trait, scientists/geneticists/researchers begin with true breeding-strains that all have identical genotypes, and then subject these individuals with identical genotypes to different environmental conditions (the reason they utilize true-breeding individuals with identical genotypes is so that the only reason differences in phenotypic expression can be found amongst these individuals is if the environment, the manipulated independent variable of the experiment impacts the phenotypic expression of the trait amongst individuals- it can't be the genotype because the genotypes of all these individuals is identical) an example of the above research is research done on Drosophila melanogaster this species has compound eyes, and these eyes are composed of many different facets that are designated by the facet number the norm of reaction, the environmental variation on the phenotypic expression of a trait showcased for facet number in genetically identical fruit flies is show in this experiment these genetically identical fruit flies developed at different temps the facet number within individuals varies with changes to temperature at a higher temp of 30 degrees celsius, the facet number is approximately 750 at a lower temp of 15 degrees celsius, the facet number is over 1000 (so the lower the temp, the higher the facet number in drosophila melanogaster)

genetic recombination

this terms designates when an offspring has a different combination of alleles than the combinations of alleles found in the parental generation independent assortment during gamete formation contributes to genetic recombination occurrences crossing over also contributes to genetic recombination occurrences due to independent assortment, humans can make over 8 million possible gametes

sex-limited inheritance

this type of inheritance refers to traits that only occur within one sex an example of this is breast development in mammals, this only occurs within the female sex Molecular: sex hormones once again may regulate and influence the molecular expression of genes, and that can influence the effect the allelic combinations of these genes has on the phenotype, and the phenotypic trait expressed sex hormones that are primarily produce in only one sex (so hormones prevalent within a single sex) are integral to influencing a certain phenotypic expression of a particular trait, they are the hormones influencing the molecular expression of a gene coding for a particular phenotype

how can a mutant allele be dominant over a wild type allele?

three explanations for dominant mutant alleles: -gain of function mutation -dominant-negative mutation -haplo-insufficiency

coat color in rodents

three phenotypes are produced by a two-gene interaction coat color in rodents showcases 3 distinct phenotypes a true breeding black rat (homozygous allelic combination) is crossed to a true breeding albino rat (homozygous allelic combination) when these two organisms are crossed with one another, the resulting offspring are rats with an agouti coat color agouti coat color- a coat with black pigmentation at the times of each hair, this black color changes to orange as you follow along the hair and get closer to the root when two agouti offspring of the first filial generation are crossed with one another, they will produce in the second filial generation agouti, black, and albino offspring the ratio of agouti: black: albino offspring in the second filial generation is 9:3:4 A- this allele is the dominant one coding for an agouti colored coat this allele A codes for a protein that regulates the hair color of the rat sol that the pigmentation on all individual hairs shifts from black (eumelanin-black pigment) to orange (phaeomelanin-orange/yellow pigment made from eumelanin) at the roots a- this allele stops the shift from black pigmentation (eumelanin) to orange pigment at the roots, and thereby results in the production of solely black pigmentation production throughout the entire length of each individual hair an animal with a homozygous recessive aa allelic combination will have an all black coat due to the effect of the a allele C- this allele codes for color the colored gene (similar to the one in rabbits) codes for the enzyme tyrosinase, which is the enzyme necessary for the metabolic pathway that leads to the production of eumelanin-black pigment, which leads to the production of phaemelenanin-orange/yellow the C allele allows pigmentation to be produced by tyrosinase c- this allele causes the loss of proper tyrosinase function, therefore tyrosinase will not function in the pathway that produces eumelanin-black pigment from which phaeomelanin-orange/yellow pigment is formed both the A/a gene allelic combinations and the C/c gene allelic combinations contributed to the morphological presentation of the rat's coat color the A allele for agouti is dominant to the a allele for black (no agouti) the C allele for color is dominant to the c allele for no color the presence of a cc in the two allelic combinations will cause the organism to be albino the c allele is epistatic to A and will mask the pigment production of an abouti colored coat that A codes for the presence of an aa in the two allelic combinations will cause the organism to be be black with no agouti pattern THIS IS NOT EPISTASIS THIS IS THE GENE MODIFIER EFFECT the gene modifier effect was the alleles of one gene modifying the phenotypic effect of the alleles of a different gene, not masking it the presence of the aa in one of the allelic combination will modify the agouti color to black

bacterial dna replication

thus far, we have considered how a complimentary and double stranded structure underlies the ability of dna to be copied thus far we have considered how a complementary and double stranded structure these features, complementarity and double helical structure, how a complementary and double stranded structure underline the ability of DNA to be copied a complementary and double stranded structure underline the ability of DNA to be copied in addition to this understanding, and the study so far of how a complemetnary and doubled stranded structure underlies the ability of the DNA to be copied the experimetns of Meselson and Stahl showed that DNA replication results in two double helices, each one containing a parental/template/original strand, and a newly synthesized, newly made, newly created daughter strand the experiments implemented by Meselson and Stahl showed that DNA replication, that an initial round of dna replication results in the formation of two double helices, the formation of two double helices, each individual helix containing one parental/template/original strand, and one newly made, newly synthesized daughter starnd we are now going to turn our attention to how dna replication actually occurs within living cells we are now going to turn our attention to how dna replication actually occurs within living cells much of the research investigating how in the world dna replication actually occurs within livings cells has focused on the bacterium Escherichia coli specifically much of the research investigating how in the world the process of dna replication occurs within living cells has focused on the bacterium Escherichia coli specifically the result of these studies, that have focused on escherichia coli in order to explain how the process of dna replication occurs within bacterial cells, the results of these studies have provided us the foundation for our current molecular understanding and comprehension of the process of dna replication the replication of the bacterial chromosome in particular the replication of the bacterial chromosome in particular is a process in which many cellular proteins participate an overview of the process of bacterial chromosomal replication the stie on the bacterial chromosome where dna synthesis begins is known as the origin of replication the site on the bacterial chromosome where dna synthesis begins is known as the origin of replication the site on the bacterial chromosome where the process of dna synthesis begins is known as the origin of replication bacterial chromosomes contain a single origin of replication bacterial chromosomes contain a single origin of replication the synthesis of new daughter strands, the synthesis of new daughter strands is initiated within this single origin of replication, and the synthesis of new daughter strands, initiated within this single origin of replication, begins in the single origin of replication within a bacterial chromosome and then proceeds in both directions, proceeds in both directions or bidirectionally around the bacterial chromosome the synthesis of new daughter strands is initiated within the origin and proceeds in both directions the synthesis of new daughter strands is initiated at the single origin of replication of the bacterial chromosome, at the single origin or replication of the bacterial dna, and proceeds bidirectionally from there, in both directions, around the bacterial chromosome two replication forks move in opposite directions outwards from that single origin of replication two replication forks move in opposite directions outwards in opposite directions from that single origin of replication of the bacterial chromosome, of the bacterial dna a replication fork what is a replication fork a replication fork is the site where the parental dna strands have separated and new daughter strands are being made a replication fork is the stie where the parental dna strands have separated from one another and new daughter strands are being made a replication fork is the site where the parental dna strands have separated from one another and new daughter strands are being synthesized, are being made there are two replication forks where the two previously intertwined in a double helix parental/template strands have separated from one another and the new daughter strands are being made/synthesized at this site where the two parenal/template strands have separated there are two replication forks extending from this single origin of replication within the bacterial chromosome within the bacterial dna these two replication forks where the two parental/template strands have separated from one another and the new daughter strands are being synthesized, these two replication forks move in opposite directions from one another as they extend from the single origin of replication eventually, these replication forks moving in opposite directions from one another meet eachother on the opposite side of the bacterial chromosome (as it is circular) in order to complete the process of bacterial dna replication the two replication forks move in opposite directions from one another but will eventually meet on the opposite side of the bacterial chromosome in order to finish out the process of replication

genetics as a discipline divisions

transmission, molecular, and population genetics overlap is found amongst these fields however

Mendel's law of independent assortment

two different genes will randomly assort their alleles during the formation of gametes/haploid cells they are not linked, and this results in more gametes with differing alleles as well as numerous allelic combinations with Mendel's experiments, the F1 self-fertilization experiment particularly, due to the law of independent assortment there are 16 possible gametic combinations for the zygotes 9 round and yellow 3 round and green 3 wrinkled and yellow 1 wrinkled and green a ratio of 9:3:3:1 the law of independent assortment details that one individual can have many genetically different gametes, with all sorts of alleles for different genes, different pairings resulting in markedly distinct zygotes

pedigree analysis

unfortunately, we are unable to control the genotypes and phenotypes of the parents that procreate in order to see results as Mendel was able to, so we use a pedigree analysis that allows us to determine the inheritance pattern that a particular gene will follow, looking at the reproduction that has already occurred pedigree analysis is utilized in order to: determine the inheritance pattern of human genetic diseases, the ways in which particular diseases are inherited throughout a family an interesting thing to investigate is whether or not the allele coding for a human genetic disease is a dominant or recessive one, where you either simply require one allele coding for the genetic disease in order for the individual to express it, or two alleles following the probability laws of the Punnet Square and melding it with a pedigree analysis helps scientists to comprehend whether or not the allele for a human genetic disease is dominant or recessive look at the patterns of how many offspring inherit this disease

variations in euploid

variations in euploid occur naturally in a few animal species variations in euploidy occur naturally in a few animal species we are now going to focus on changes in the number of sets of chromosomes, this is referred to as variations in euploidy, as euploidy has to do with whether the total number of chromosomes within the genome of an organism is a multiple of a single set of chromosomes within the genome of that organism there can be changes in the number of sets of chromosomes there can be changes in the number of sets of chromosomes, variations in euploidy the majority of species of animals are diploid the majority of species of animals are diploid in some cases, changes in euploidy are not well tolerated in some cases, changes in euploidy are not well tolerate for example, polyploidy occurring in animals tends to be a lethal condition, where the embryo with this polyploid condition will not be able to develop properly polyploidy in mammals tends to be a lethal condition polyploidy in mammals tends to be a lethal condition, commonly tends to be a lethal condition in haplodiploid species, which include many species of bees, wasps, and ants, one of the sexes is haploid, usually the male, and the other sex is diploid, usually the female in haplodiploid species, haplodiploid species include many species of bees, wasps and ants, one of the sexes is haploid, usually the male, and the other sex is diploid, usually the female in haplodiploid species which include many species of bees, wasps and ants, there tends to be a haploid sex, usually male, and then a diploid sex, usually female an example of a haplodiploid species where there is one sex that is haploid, usually the male, and one sex that is diploid, usually female a haplodiploid organism, haplodiploid includes many species of bees, wasps, and ants in bees, which are in that haplodiploid category, there are male bees, which are called drones these male bees that are called drones contain a single set of chromosomes within them these male bees that are called drones contain a single set of chromosomes within them these male bees that are called drones contain a single set of chromosomes within them these male bees are identified as drones and they contain a single set of chromosomes within them these males, that are known as drones, and are haploid, containing a single set of chromosomes, are usually produced from unfertilized eggs by comparison, female bees are produced from fertilized eggs and are diploid by comparison, female bees are produced from fertilized eggs and are diploid female bees within the bee species are produced from fertilized eggs and are diploid this is an example of a haplodiploid species there are more examples of vertebrate polyploid animals there are more examples of vertebrate polyploid animals there have been many examples of vertebrate polyploid animals that have been discovered interestingly there have been several occasions, where there are animals that are morphologically v similar, and can be found as a diploid species as well as a separate polyploid species interestingly there have been several occasions where there are morphologically similar animals that you would presume to be within the same species but in fact can be found as a diploid species as well as a polyploid species this situation, of morphologically similar animals being found in a diploid species as well as a polyploid species this situation of morphologically similar animals being found in a diploid species as well as a polyploid species, occurs among particular amphibians and reptiles there are photographs that have been taken of a diploid and a tetraploid, a 4n frog containing 4 sets of chromosomes they look indistinguishable from one another, these two frogs are v morphologically similar, however one comes from a diploid species, containing 2 sets of chromosomes, and the other comes from a polyploid species, containing 4 sets of chromosomes, a tetraploid species their difference, the difference bw these two frogs that are essentially morphologically identical, can only be revealed by an examination of the chromosome number in the somatic cells of the animals, where it can be seen that one frog is diploid, containing two sets of chromosomes, and the other frog is tetraploid containing four sets of chromosomes these two frogs can also be distinguished by their mating class H. chrysoscelis has a faster trill rate than H. versicolor

inversions and their lack of phenotypic consequences

we are now going to analyze inversions what are inversions, INVERSIONS ARE CHANGES IN CHROMOSOME STRUCTURE THAT INVOLVE A REARRANGEMENT IN GENETIC MATERIAL inversions are changes in chromosome structure that involve a rearrangement in chromosomal material, a rearrangement of genetic material, a rearrangement of DNA sequences is designated as an inversion in a chromosomal inversion, there is a rearrangement of the genetic material composing that chromosome a chromosome containing an inversion (a rearrangement of genetic material) contains a chromosomal segment that has been flipped to the opposite direction a chromosome containing an inversion, a rearrangement of chromosomal material, a rearrangement of genetic material, contains a chromosomal section, that is flipped to the opposite side, flipped in the opposite direction or inverted how do geneticists classify inversions? how do geneticists classify inversions? geneticists classify inversions by the location of the centromere, they classify inversions through the analysis of the location of the centromere IF THE CENTROMERE LIES WITHIN THE INVERTED REGION OF THE CHROMOSOME THEN THE INVERTED REGION IS DESIGNATED AS A PERICENTRIC INVERSION a pericentric inversion is the designation given to a chromosomal segment where the centromere lies within the inverted chromosomal segment, the centromere lies within the inverted chromosomal segment, this is designated as a pericentric inversion WITHIN I- WITHIN if the centromere is found outside of the inverted region, outside the chromosomal segment that underwent a flip in the opposite direction, an inversion, then this is designated as a PARACENTRIC inversion AAAAA a paracentric inversion, where the centromere is located outside of the inverted chromosomal region it is located outside of the chromosomal region that was flipped when a chromosome contains an inversion, the total amount of genetic material remains he same, the same amount as it is within a normal chromosome when a chromosome contains an inversion, the total amount of genetic material remains the same, it remains the same amount as it is within a normal chromosome that has not experienced an inversion, it contains the same amount of genetic material as a chromosome that has not undergone an inversion, there is no loss of genetic material within a chromosome containing an inversion, merely a rearrangement of genetic material, a rearrangement of chromosomal material, genetic material resulting in an inverted chromosomal segment, a chromosomal segment that has been flipped in the opposite direction in rare cases however, an inversion can alter the phenotype of an individual, an inversion can alter the phenotype of an individual whether or not this occurs, the impact to the phenotype of an individual due to an inversion, is related to the boundaries of the inverted chromosomal segment whether or not the chromosomal inversion has an impact on the phenotype of the individual w this chromosomal inversion depends upon the boundaries of the chromosomal segment when an inversion occurs, the chromosome is broken in two places when a chromosomal inversion occurs, the chromosome is broken in two places, and the center piece, the center piece in the middle of the two side segments, flips around in order to produce the inversion, the rearrangement of genetic material if either breakpoint occurs within a vital gene, if within either location that the chromosome breaks in order to bring out the center segment that will be flipped around in order to cause a chromosomal inversion, if within either breakpoint, there is a vital gene, THE FUNCTION OF THE GENE within this breakpoint is expected to be impacted and affected, this will potentially produce a phenotypic effect, this will potentially produce a phenotypic impact, the phenotype of the individual may be affected an example of how an inversion how a chromosomal inversion can impact the phenotype of an individual, there are some people with hemophilia, specifically type A hemophilia there are some individuals with type A hemophilia, and they have inherited an X-linked inversion, an inversion on one of their X chromosomes containing a gene that influences and impacts whether or not an individual particularly has type A hemophilia the breakpoint for this X-linked inversion, the area of the chromosomes, on of the areas of the chromosome that breaks in order for the inversion to occur, this breakpoint has inactivate the gene for factor VIII- a blood clotting protein a breakpoint in this X-linked inversion, individuals with type A hemophilia has inactivated the gene for factor VIII so there is a gene that codes for factor VIII, a blood clotting protein that is inactivated due to a chromosomal inversion on an X chromosome, the X chromosome being linked to the type A hemophilia condition in other cases, an inversion or translocation may reposition a gene or reposition a chromosome in a way that alters the normal level of expression of a particular gene, and perhaps the normal level of function of that gene due to the level of expression of that gene being altered this is known as the position effect, where an inversion or a translocation may reposition a particular gene on a chromosome in a way that alters the normal level of expression of that particular gene the position effect is where an inversion or a translocation may reposition a particular gene on a chromosome in a way that alters the normal level of expression of that particular gene the position effect is where a change in phenotype occurs because the position of a gene changes from one chromosomal site to a different location the position effect is where a change in phenotype occurs bc the position of a gene changes from one chromosomal site to a different location an inversion or a translocation cause a change in the chromosomal site location for a gene that causes the normal level of expression of that gene to be altered, which results in a phenotypic change within the organism that contains that gene INVERSIONS SEEM LIKE AN UNUSUAL GENETIC PHENOMENON they appear to be an unusual genetic phenomenon, however within populations, inversions appear in larger numbers in significant numbers within human populations about 2 percent inversions in human populations are found in significant numbers about 2 percent of the human population carries inversions that are detectable with a light microscope about 2 percent of the human population carries inversions that are detectable with a light microscope about 2 percent of the human population carries inversions that are detectable with a light microscope in the majority of cases, such individuals are phenotypically normal and live their lives without knowing that they carry an inversion in the majority of cases, such individuals are phenotypically normal and live their lives without knowing that they carry an inversion, the majority of individuals within that 2 percent of the population that carry inversions in a few cases however an individual with an inversion chromosome may produce offspring iwht phenotypic abnormalities in a few cases an individual with an inversion chromosome may produce offspring with phenotypic abnormalities this event may then prompt a physician to request a microscopic examination of the individual's chromosomes, if a phenotypically normal individual gives rise to an offspring with phenotypic abnormalities, if a phenotypically normal individual contributes to phenotypically abnormal offspring, the physician will potentially request a microscopic examination of the individual's chromosomes to see whether or not they have chromosomal inversions that they were not aware of in this way, phenotypically normal individuals may discover that they have a chromosome with an inversion in this way phenotypically normal individuals may discover that they have a chromosome with an inversion that did not impact their phenotype, but whose contribution in regards to the genetic material of their offspring, formed by a gamete probably containing this chromosomal inversion, affected the phenotype of their offspring

the information we can glean from loss of function alleles

we can use loss of function alleles in order to understand the role of a protein within an organism (the protein coded for by the gene that this allele is a part of, the gene that this allele contributes to in the form of an allelic combination) an example of our understanding is that we would imagine the gene that affects flower color (whether the flower is purple or white) probably codes for a protein responsible for pigmentation, pigment production we can possibly conclude that the white allele (the allele coding for a white pigment, and therefore a white flower) is a loss of function allele, coming about due to a mutation that renders the normal enzyme (that codes for purple pigment production) useless the scientist trying to draw this conclusion would probably analyze the petals from purple and white flowers and try to discover the protein absent in the white flowers but present in the purple flowers, proving that the protein is responsible for purple pigment production, and its absence means that it will not code for purple pigment, and the flower will present as white

variations in euploidy are common in plants

we now turn our attention to variations of euploidy that occur in plants there are variations of euploidy that occur in plants compared with animals, plants more commonly exhibit euploidy compared with animals, plants more commonly exhibit euploidy among ferns and flowering plants, at least 30 to 35% of the species are polyploid among ferns and flowering plants, at least 30 to 35 percent of the species among ferns and flowering plants are polyploid, speaking to how polyploidy is more prevalent within plants POLYPLOIDY IS ALSO IMPORTANT IN AGRICULTURE polyploidy is also important in agriculture polyploidy is also important in agriculture polyploidy is also important in agriculture polyploidy is also important in agriculture many of the fruits and grains that we eat are produced from polyploid plants many of the fruits and grains that we eat are produced from polyploid plants many of the fruits and grains that we eat are produced from polyploid plants many of the fruits and grains that we eat are produced from polyploid plants for example, an example of how many of the fruits and grain that we eat are produced from polyploid plants the species of wheat that we utilize in order to make bread the species of wheat that we utilize in order to make bread the species of wheat that we utilize in order to make bread the species of wheat that we utilize in order to make bread the species of wheat that we use to make bread is Triticum aestivum this species of wheat that we utilize to make bread is tritcum aestivum is hexaploid this species of wheat that we utilize in order to make bread is tritium aestivum and it is a hexaploid, 6n, containing 6 sets of chromosomes, and this species of wheat that we utilize in order to make bead, tritium aestivum which is a hexaploid arose from the union of diploid genomes from 3 closely related species triticum aestivum arose from the union of diploid genomes from 3 closely related species different species of strawberries are: diploid tetraploid hexaploid octaploid different species of strawberries are: diploid tetraploid hexaploid octaploid there are many instances in which polyploid strains of plants display outstanding agricultural characteristics these strands of plants, these polyploid strains of plants can display outstanding agricultural characteristics, usually being larger in size and more robust as well these traits of being larger in size as well as more robust are more advantageous in regards to the production of food in addition to this, polyploid plants tend to exhibit a greater adaptability in addition to this, polyploid plants tend to exhibit a greater adaptability in addition to this, polyploid plants tend to exhibit a greater adaptability, which allows them to withstand harsher environmental conditions polyploid plants tend to exhibit a greater adaptability which allows them to withstand harsher environmental conditions polyploid ornamental plants oftentimes produce larger flowers than their diploid counterparts polyploid ornamental plants oftentimes produce larger flowers than their diploid counterparts POLYPLOID PLANTS HAVING AN ODD NUMBER OF CHROMOSOME SETS such as triploids (3n) or pentaploids (5n), are usually unable to reproduce polyploid plants that have an odd number of chromosome sets such as triploids (3n) or pentaploids (5n) are usually unable to reproduce why are these polyploid plants with an odd number of chromosome sets unable to reproduce these polyploid plants with an odd number of chromosome sets are unable to reproduce they are sterile the sterility of these polyploid plants with an odd number of sets of chromosomes arises because they produce highly aneuploid gametes, gametes with particular types of chromosomes the number of copies of those particular types of chromosomes impacted and altered the sterility of these polyploid plants with an odd number of sets of chromosomes arises due to these polyploid plants produce highly aneuploid gametes during prophase I of meiosis I, homologous pairs of sister chromatids form bivalents during prophase I of meiosis I, homologs pairs of sister chromatids form bivalents during prophase I of meiosis I, homologous pairs of sister chromatids forms bivalents during prophase I of meiosis I, homologous pairs of sister chromatids form bivalents however, organisms containing an odd number of chromosomes, such as 3, display an unequal separation of homologous chromosomes during anaphase I of meiosis I however, organisms containing an odd number of chromosomes such as 3 chromosomes rather than 2 or 4, any even number of chromosomes, display an unequal separation of homologous chromosomes during anaphase I of meiosis I during anaphase I of meiosis I, there is an unequal separation of homologous chromosomes that occurs during anaphase I of meiosis I, there is an unequal separation of homologous chromosomes, of homologous pairs of sister chromatids that occurs during anaphase I of meiosis I an odd number of chromosomes cannot be equally divided amongst daughter cells, that can simply not occur for each type of chromosomes, a daughter cell will end up randomly getting one or two copies of each type of chromosoem for example one daughter cell may receive: one copy of chromosome 1 two copies of chromosome 2 two copies of chromosome 3 one copy of chromosome 4 and so forth, due to unequal separation of pairs of sister chromatids, of chromosomes during anaphase I of meiosis I that subsequently impacted the separation of pairs of sister chromatids into individual components designated as chromosomes during anaphase II of meiosis II for a triploid species that contains many different chromosomes within a single set of chromosomes, and contains 3 sets of these chromosomes, meiosis is v unlikely to produce a daughter cell that is euploid, v unlikely to produce a daughter cell whose total number of chromosomes is a multiple of 1 set of chromosomes if we assume that a daughter cell receives either one copy or two copies of each kind of chromosome we assume that a daughter cell receives either one copy or two copies of each type of chromosome due to the triploid nature of the cell producing the daughter cells, the probability that meiosis will produce a cell that is perfectly haploid or diploid is (1/2)^(n-1) n is equal to the number of chromosomes within a set an example that showcases this probability and the low probability of producing a daughter cell that is euploid, either haploid or diploid where its total number of chromosomes is a multiple of a single set of chromosomes there is a triploid organism, containing 3 sets of chromosomes this triploid organism contains 3 sets of chromosomes, each set of chromosomes contains 20 chromosomes per set the calculated probability of producing a euploid daughter cell, either a haploid or a diploid daughter cell is 0.000001907, or 1 in 524,288, calculated utilizing the formula of (1/2)^(n-1), which is (1/2)^(19), because of the number of chromosomes within a set being 20 meiosis is almost certain to produce cells that contain one copy of some chromosomes and two copies of other types of chromosomes when the original cell has an odd number of sets of chromosomes this high probability of aneuploidy within the daughter cells produced by an organism with an odd number of sets of chromosomes underlies the reason for triploid sterility, which a triploid organism will not be able to participate in producing a viable embryo STERILITY IS GENERALLY A DETRIMENTAL TRAIT as there is no longer the ability of a sterile organism to reproduce however, it can be advantageous in regards to agriculture, as sterility can result in a seedless fruit an example of how sterility can lead to a seedless fruit examples are domestic bananas and seedless watermelons that are of the triploid variety, and due to the odd number of sets of chromosomes, are sterile and unable to reproduce the domestic banana that we have today was originally derived from a seed producing diploid species, a diploid species that had seeds and was able to reproduce due to having an even number of chromosomes the domestic banana was derived from a seed producing diploid species, and the domestic banana was then asexually propagated by humans via cuttings the small black spots found in the center of a domestic banana are degenerate seeds, seeds that degenerated over time due to the asexual propagation of the domestic banana via cuttings there is also the case of flowers, the seedless phenotype of flowers can also be beneficial the seedless phenotype of flowers can also be beneficial seed producers, seed producers such as Burpee, they have developed triploid varieties of flowering plants such as marigolds, that due to their odd number of chromosome sets are sterile and cannot reproduce the triploid marigolds due to their odd number of sets of chromosomes are unable to set seed, so the majority of their energy instead of going towards reproduction, goes towards flower production apparently, according to Burpee, the creator of these triploid marigolds, "they bloom and bloom, unweakened by seed bearing" they focus their energy on flowering rather than seed bearing, the focus their energy on flower production rather than seed bearing bc they are sterile

genome

what is a genome a genome is a term referring to a complete set of genetic material in a particular cellular compartment it is referring to a COMPLETE SET, AN ENTIRE ENTITY OF GENETIC MATERIAL found within a particular cellular compartment, in the majority of cases, the nucleus or nucleoid region is what they are referring to however they could also be referring to the cellular compartments of the chloroplast and mitochondria, which contain their own genetic material the genome is a term designating the entirety of genetic material found within a particular cellular compartment, oftentimes the entirety of the genetic material of that organism that is whose composition includes that cell and that cell's particular cellular compartment housing the genetic material what is a bacterial genome? a bacterial genome is the genome, the entire entity of genetic information, the complete set of genetic information and material found within a bacterial cell the genome for bacteria is usually ONE SINGLE CIRCULAR CHROMOSOME for bacteria, it is usually ONE SINGLE DOUBLE STRANDED CIRCULAR CHROMOSOME what is a eukaryotic genome? within eukaryotic cells, when the term genome is utilized, it is utilized in order to designate the COMPLETE SET OF CHROMOSOMES RESIDING WITHIN A EUKARYOTIC CELL'S NUCLEUS the genome designates the complete set of chromosomes residing within the nucleus of a eukaryotic cell referring to the genome of the human, we would be referring to the complete set of genetic material found within the nucleus of a human's cells, the complete set of 46 chromosomes composed of 23 pairs, 2 homologous chromosomes to a pair, 1 inherited from each parent when we refer to the nuclear genome, we refer to ONE COMPLETE SET OF CHROMOSOMES THAT RESIDES WITHN THE CELL NUCLEUS we, when utilizing the term nuclear genome, are referring to ONE COMPLETE SET OF CHROMOSOMES RESIDING WITHIN THE CELL NUCLEUS this is the haploid component of chromosomes, the HAPLOID COMPONENT IS CONSIDERED A NUCLEAR GENOME eukaryotes have a mitochondrial genome eukaryotic cells, specifically plant cells contain a chloroplast genome usually when utilizing the term eukaryotic genome, we are referring to the nuclear genome AND THAT HAPLOID COMPONENT OF CHROMOSOMES RESIDING WITHIN THE NUCLEUS, AS THAT IS CONSIDERED ONE COMPLETE SET AND IS FOUND WITHIN THE NUCLEUS

genetic variation

what is genetic variation? genetic variation is a term utilized to designate the phenomenon of genetic differences that are present among members of the same species, or genetic differences that are present among members of different species the term genetic variation is used to designate the genetic differences and variation, the genetic differences that are present bw members of the same species, or can be utilized in order to designate the genetic differences that are present bw members of different species essentially the term genetic variation is utilized to describe genetic differences, difference in genes, the DNA sequences that encode these gene, the distinct morphological, physiological, and behavioral characteristics that result from the alterations and differences in genotype, that occurs within a particular species, or amongst a variety of species allelic variation specifically refers to variation occurring in specific genes, differences being found within species or amongst a variety of species where there are differences occurring within a specific gene this is designated as allelic variation however, in this chapter, rather than focusing on allelic variation, the genetic differences and individual may find within a population having to do with a specific gene, and the DNA sequence encoding this gene differing from analyzed organism to analyzed organism rather than focusing on specific genes, and how specific genes can present with different allelic combinations and therefore different phenotypic expressions as one moves a genetic analysis from one member of a species to another member, or one member of one species, to a member of a different species rather than focusing on the differences that can occur within a species or amongst species in regards to specific allelic combinations that constitute a specific gene, Chapter 8 will be focusing on LARGER TYPES OF GENETIC CHANGES chapter 8 will be focusing on LARGER TYPES OF GENETIC CHANGES, LARGER KINDS OF GENETIC VARIATION LARGER TYPES OF GENETIC CHANGES we will be looking at LARGER TYPES OF GENETIC CHANGES THAT IMPACT THE STRUCTURE OR NUMBER OF EUKARYOTIC CHROMOSOMES we will be looking at larger genetic changes that impact the structure or number of eukaryotic chromosomes we will be analyzing larger genetic changes that impact the structure or the totality, the number of eukaryotic chromosomes within an individual's cells these larger genetic alterations that affect the structure or the number of eukaryotic chromosomes MAY AFFECT THE EXPRESSION OF MANY GENES these larger genetic changes, these larger genetic alterations that occur can affect the expression of a multitude of genes rather than just one, and therefore cause dramatic changes and variation in an individual's genotype these larger genetic variations, these larger genetic changes can affect a multitude of genes due to a portion of a chromosome or the totality of the number of chromosomes in a eukaryotic individual's cells being affected, and therefore dramatically affect and alter the phenotype of an individual, causing substantial and dramatic variation VARIATION IN CHROMOSOME STRUCTURE AND NUMBER ARE ENORMOUSLY IMPORTANT IN GENETICS variation in chromosome structure and number are enormously important in genetics variation in chromosome structure and the totality of the number of chromosomes is extremely important in genetics these two topics of variation in chromosome structure and the totality of the number of chromosomes are extremely important within the genetics bc they ARE CRITICAL IN THE EVOLUTION OF NEW SPECIES they also have widespread medical relevance the topics of variation in chromosome structure and the totality of the number of chromosomes are extremely important within the field of genetics bc the topics of variation within chromosome structure and variation within the totality of the number of chromosomes are extremely important in regards to influencing the evolution of a new species these two aforementioned topics of variation in chromosome structure and variation in regards to the Toal number of chromosomes occupying a eukaryotic individual's somatic cells are critical in bringing about the evolution of a new species the variation in the structure of a chromosome or the total number of chromosomes found within a eukaryotic individual's somatic cells HAVE GREAT MEDICAL RELEVANCE in addition to the relevance of the variation in the structure of chromosomes and the total number of chromosomes found within a eukaryotic individual's somatic cells within genetics, evolution, the medical field, it also has important within agriculture agricultural geneticists have discovered that variation occurring within the structure of chromosomes, or the total number of chromosomes found within a eukaryotic individual's somatic cells can lead to the development of new crops the development of new crops can occur due to the variation in chromosomal structure and the total number of chromosomes within a eukaryotic organism's somatic cells, according to the research implemented by agricultural researchers, and this can be quite profitable

molecular genetics

what is molecular genetics molecular genetics is the study of DNA structure and function at the molecular level what is an exciting goal of molecular genetics an exciting goal of molecular genetics is using our knowledge of the structure of DNA in order to understand how in the world DNA functions as the genetic material, why and how DNA is our genetic material, how it is constructed, what it is composed of, and how it functions in causing and influencing phenotypic expressions of traits through the utilization of molecular techniques, researchers have been able to establish and determine the organization of many of our genes through the utilization of molecular techniques, researchers have been able to establish and determine the organization of many of our genes researchers have been able to establish and determine the organization of many of our genes through the utilization of molecular techniques researchers have been able to establish and determine the organization of many of our genes through the utilization of molecular techniques this information that we have gleaned about the order and organization of all of the genes within our genome has allowed us to understand how the expression of these genes influence and govern the outcome of an individual's traits there have been dramatic and substantial advances in the techniques and approaches to investigate and alter genetic material DNA- deoxyribonucleic acid RNA- ribonucleic acid

what steps led to the formation and organization of metaphase chromosomes?

what steps led to the organization and formation of metaphase chromosomes? how in the world are metaphase chromosomes formed and organized? metaphase chromosomes are formed and organized in a particular manner, this particular manner in which metaphase chromosomes are formed and organized is one that researchers have been investigating and attempted to understand during the past several years, for the past several years, there have been studies conducted in yeast and frog oocytes THERE HAVE BEEN STUDIES CONDUCTED IN YEAST AND FROG OOCYTES there have been studies conducted in the oocytes, the egg cells of yeast and frogs this research implemented, these studies conducted on the oocytes, the eggs of yeast and frogs this research that has been implemented, these studies conducted on the oocytes, these studies conducted on the eggs of yeast and frogs have been aimed at the IDENTIFICATION OF PROTEINS THAT PROMOTE THE CONVERSION OF INTERPHASE CHROMOSOMES INTO METAPHASE CHROMOSOMES the studies conducted on the eggs, on the oocytes of yeast and frogs have been aimed at identifying the proteins that promote the conversion of interphase chromosomes to metaphase chromosomes these studied conducted on the oocytes of yeast and frogs have been aimed at identifying the proteins that are responsible for the conversion of interphase chromosomes, which are still in the euchromatic state, fairly decompacted, decondensed, and transcriptionally active, to metaphase chromosomes, which are extremely compacted with a diameter of 1400nm spanning the two sister chromatids joined by a centromere in order to form a chromosome, and transcriptionally inactive the studies conducted and implemented on the oocytes/eggs of yeast and frogs have had the objective of identifying the proteins that are involved in the conversion of interphase chromosomes to metaphase chromosomes IN YEASTS- mutants have been characterized in the studies implemented on the oocytes/eggs of yeast, there have been mutants that have been characterized mutants within yeast have been characterized these mutant that have been characterized in yeast HAVE ALTERATIONS IN THE CONDENSATION OR THE SEGREGATION OF CHROMOSOMES these mutants that have been characterized in yeast have alterations in the condensation or the segregation of chromosomes these mutants that have been characterized in yeast, have alterations in the condensation or the segregation of chromosomes these identified and characterized mutants found within the oocytes of yeast have alterations in the condensation or the segregation of chromosomes, have influence over the condensation and compaction or segregation and sorting of chromosomes there have also been biochemical studies conducted and implemented on the oocytes of frogs in addition to the oocytes of yeast the biochemical studies conducted and implemented on the oocytes of frogs in addition to the oocytes of yeast have resulted in the following: THE PURIFICATION OF PROTEIN COMPLEXES THAT PROMOTE CHROMOSOMAL CONDENSATION OR PROMOTE SISTER CHROMATID ALIGNNMENT in these studies implemented upon the oocytes of frogs, the purification of proteins has occurred the purification of proteins that are responsible for and have an influence over the condensation/compaction of chromosomes or the alignment of sister chromatids when they are forming chromosomes, single individual entities due to being bound and joined at a centromere, and the alignment of sister chromatids joined by a centromere throughout the phases of the cell cycle (perhaps metaphase of mitosis, when these sister chromatids are joined by a centromere to form an individual chromosome these two lines of independent research conducted on the oocytes of frogs and yeast, similar discoveries were made of proteins responsible for/having an enormous impact and influence upon the conversion of interphase chromosomes, interphase chromosomes that are decompacted, decondensed, and transcriptionally active chromosomes to metaphase chromosomes, compacted, condensed, to a diameter of 1400 nm, and transcriptionally inactive chromosomes researchers discovered through these implemented experiments done upon the oocytes of yeast and frogs, that CELLS CONTAIN TWO MULTIPROTEIN COMPLEXES that yield a lot of influence over the conversion of interphase chromosomes to metaphase chromosomes, that control, influence, and maintain the compaction and condensation of chromosomes, as well as the alignment of chromosomes and the alignment of the sister chromatids that compose these chromosomes these two multi protein complex that cells contain that have such influence over the introduction, maintenance, and consistency of chromosome compaction/condensation, and the sorting/organization of chromosomes and the sister chromatids that compose these chromosomes during the cellular division process of mitosis and the gamete formation processes of meiosis I and 2 are CONDENSIN AND COHESIN the two multi protein complexes that wield a lot of influence over the introduction, alteration and maintenance of chromosome condensation/compaction and the organization/sorting of chromosomes and the sister chromatids that compose them are CONDENSIN AND COHESIN the two multiprotein complexes are condensing and cohesin these two multi protein complexes, condensin and cohesin PLAY A CRITICAL ROLE in chromosomal condensation and sister chromatid alignment THESE TWO MULTIPROTEIN COMPLEXES, CONDENSIN AND COHESIN PLAY A CRITICAL ROLE IN CHROMOSOMAL CONDENSATION/COMPACTION and the ALIGNMENT/ORGANIZATION OF SISTER CHROMATIDS THAT COMPOSE CHROMOSOMES, respectively so condensin plays a particular role in the condensation/compaction of chromosomes, while cohesin plays a role in the organization and alignment of sister chromatids that compose chromosomes CONDENSIN AND COHESIN ARE TWO COMPLETELY DISTINCT COMPLEXES condensin and cohesin are TWO COMPLETELY DISTINCT COMPLEXES condensin and cohesin are two completely distinct, independent, individualized entities HOWEVER both the condensin and cohesin multi protein complexes contain A CATEGORY OF PROTEINS IDENTIFIED AS SMCs both the multi protein complexes of condensin and cohesn contain the particular category of proteins designated as SMC proteins what does SMC stand for? when I say SMC proteins what am i referring to SMC stands for STRUCTURAL MAINTENANCE OF CHROMOSOMES the multi protein complexes of condensin and cohesin contain the same category of proteins, SMC proteins otherwise designated as STRUCTURAL MAINTENANCE OF CHROMOSOMES PROTEINS These structural maintenance of chromosomes proteins, a category of proteins found in the multi protein complexes of condensin and cohesin, USE ENERGY FROM ATP IN ORDER TO CATALYZE CHANGES AND ALTERATIONS THAT OCCUR AND CAN OCCUR WITHIN CHROMOSOME STRUCTURE so within the multi protein complexes of condensin and cohesin, there is a category of proteins common to both of them, a category of proteins known and designated as SMC proteins, or STRUCTURAL MAINTENANCE OF CHROMOSOMES PROTEINS these are structural maintenance of chromosomes proteins that are common to both the multi protein complex of cohesin and the multiprotein complex of condensin, despite these two different and distinct individualized multi protein complexes serving different purposes the condensin serves the purpose of introducing, incorporating, altering, and maintaining the condensation/compaction of chromosomes the cohesin plays the role of introducing, incorporating, altering, and maintaining the alignment and organization of sister chromatids that join together in order to form individual chromosomes the structural maintenance of chromosomes proteins that are common to the multi protein complexes of condensin and cohesin UTILIZE ENERGY THAT COMES FROM ATP IN ORDER TO CATALYZE CHANGES AND ALTERATIONS WITHIN CHROMOSOMAL STRUCTURE the structural maintenance of chromosomes proteins that are common to the multi protein complexes condensin and cohesin utilize energy from ATP in order to catalyze and initiate changes and alterations within chromosome structure the structural maintenance of chromosomes proteins that SMC proteins that are common to these multi protein complexes condensin and cohesin utilize energy from ATP in order to catalyze and initiate changes and alterations in chromosomes structure TOGETHER WITH TOPOISOMERASES, SMC proteins, that are common to the multi protein complexes of condensin and cohesin and utilize energy from ATP in order to initiate and introduce alterations and changes to chromosomal structure the SMC proteins the structural maintenance of chromosomes proteins work together with topoisomerases in order to PROMOTE MAJOR CHANGES IN THE STRUCTURE OF DNA recall that topisomerases are protein that are responsible for the winding and supercoiling of DNA in conjunction with the topoisomerases, the SMC proteins are found to be able to cause dramatic and substantial changes within chromosomal structure MAJOR CHANGES IN DNA STRUCTURE major alterations in dna structure are promoted by the combination of SMC proteins and topoisomerases there is an emerging theme, an overall theme and concept to SMC proteins this emerging theme for SMC proteins is that SMC PROTEINS: actively fold tether manipulate DNA strands the emerging them for SMC proteins is that these proteins ACTIVELY FOLD TETHER AND MANIPULATE DNA STRANDS the SMC proteins are responsible for actively folding, tethering/anchoring and manipulating/maneuvering DNA strands these SMC proteins, structural maintenance of chromosomes proteins ARE DIMERS that have a v-shaped structure, these SMC proteins are compose of two units, and these SMC proteins that promote chromosomal alterations and are responsible for the folding/compaction, tethering/anchoring, and manipulation/maneuvering of DNA are composed of two units and have a V shaped structure THE MONOMERS of this protein structure, the monomers of the SMC entity ARE CONNECTED AT A HINGE REGION the monomers composing an SMC protein are connected at a hinge region the hinge region is where the two monomers composing an SMC protein are connected to one another these two monomers of the SMC protein that are connected at a hinge region HAVE TWO LONG COILED ARMS WITH A HEAD REGION THAT BINDS ATP these two monomers composing the SMC protein that are connected at a hinge region have TWO LONG COILED ARMS WITH A HEAD REGION THAT IS ABLE TO BIND AND WILL BIND ATP the length of each individual monomer that connect at the hinge region is 50 nm 50 nm is EQUAL TO 150 BASE PAIRS OF DNA each monomer composing the SMC protein is 50 nm long, composed of 150 base pairs

cell division

when cells prepare to divide CHROMOSOME CONDENSATION INCREASES when cells prepare to divide, chromosome condensation increases the CHROMOSOMES BECOME EVEN MORE CONDENSED the chromosomes become even more condensed as the cells prepare to divide this further condensation of the chromosomes, the chromosomes becoming even more condensed as the cells prepare to divide, assists in their proper sorting during metaphase the further condensation and compaction of these chromosomes that occurs during the process of cells preparing to divide occurs due to the necessity of proper and appropriate sorting of chromosomes and genetic material that occurs during metaphase, the condensation and compaction of chromosomes assists this process of sorting the chromosomes during metaphase what are the levels of compaction that result in a metaphase chromosome, the phase in which a chromosome is most compacted with a diameter of about 1400 nm? during interphase, the phase occurring just before mitosis the process of cellular division (nucleic division particularly, followed by cytokinesis which officially divides up the two cells, while mitosis specifically splits a single nucleus into two), during interphase the CHROMOSOMAL DNA IS FOUND IN EUCHROMATIN, a decompacted, decondensed form dna is found in euchromatin, it is found in a decompacted, decondesned form when the cells are in interphase when the chromosomes are found in euchromatin, the chromosomes are found in the following conformation: the 30 nm fibers form radial loop domains these radial loops domains that are formed by the 30 nm fibers of the chromosomal dna of a cell in interphase are anchored and attached to a protein scaffold the avg distance that loops radiate from the protein scaffold is 300 nm so their DIAMETER IS 300 nm the radial loops radiate from the protein scaffold they are attached to by about 300 nm so the diameter of the compacted DNA at this point is considered to be 300 nm THIS STRUCTURE IS THEN FURTHER COMPACTED, THIS STRUCTURE CAN AND WILL BE FURTHER COMPACTED how can this structure of the radial loops formed by 30 nm fibers, these radial loops being attached to a protein scaffold and radiating out about 300nm, giving the dna a diameter of 300 nm be further compacted? this structure can be further compacted via ADDITIONAL FOLDING OF THE RADIAL LOOP DOMAINS AND THE PROTEN SCAFFOlD this structure can be further compacted, the dna can undergo further compaction past this structure of radial loops attached to a protein scaffold radiating out 300nm (recall that these radial loops are form by the folding of 30 nm fibers into the new conformation of radial loops) through ADDITIONAL FOLDING OF THESE RADIAL LOOP DOMAINS as well as the protein scaffold that these radial loop domains are attached to this additional level of compaction GREATLY SHORTENS THE OVERALL LENGTH OF A CHROMOSOME, and it produces a DIAMETER OF APPROXIMATELY 700nm this additional level of compaction of folding of the radial loop domains and the protein scaffold that these loop domains are attached to shortens the overall length of the chromosome as well as increases the diameter to 700 nm during interphase, the majority of chromosomes are euchromatic however, during interphase particular regions of these majority euchromatic, therefore decompacted, decondensed, and transcriptionally active chromosomes are heterochromatic, these particular regions such as those near centromeres are heterochromatic, compacted, condensed, and transcriptionally inactive as cells enter the mitotic phase, the level of compaction CHANGES DRAMATICALLY the level of compaction of chromosomes changes dramatically by the end of prophase, sister chromatids are ENTIRELY HETEROCHROMATIC by the end of prophase, sister chromatids are ENTIRELY HETEROCHROMATIC, the sister chromatids are completely compacted and condensed and transcriptionally active by the conclusion of prophase of the mitotic phase two parallel sister chromatids hav e larger diameter of APPROXIMATELY 1400 NM but they have a much shorter length when compared to the lengths of the majority euchromatic chromosomes (with particular regions of heterochromatin, located near the centromere of these chromosomes) THESE HIGHLY CONDENSED METAPHASE CHROMOSOMES UNDERGO LITTLE GENE TRANSCRIPTION these highly condensed metaphase chromosomes undergo little gene transcription these highly condensed metaphase chromosomes undergo little gene transcription why do these highly condensed and compacted metaphase chromosomes under v little gene transcription and why are they overall for the most part transcriptionally inactive? this is because it is difficult for transcription proteins to gain access to this highly compacted dna as long as the dna is in this highly compacted state, it cannot be genetically transcribed the dna cannot be genetically transcribed as long as it is in this highly compacted state, particularly in this highly compacted state of metaphase chromosomes these metaphase chromosomes that are highly compacted due to the further folding of radial loop domains and the protein scaffold they are attached to, resulting in a length shorter than that of chromosomes in interphase, as well as a diameter of 1400nm, the chromosome is not transcriptionally active THE MAJORITY OF TRANSCRIPTIONAL ACTIVITY CEASES AND STOPS DURING M PHASe the majority of transcriptional activity ceases and stops during the mitotic phase, due to the further and increased compaction and condensation of chromosomes, that makes the chromosomal dna inaccessible to transcription protein a few specific genes may be transcribed during the mitotic phase of the cell however the mitotic phase is generally a short period of the cell cycle in highly condensed chromosomes, such as the chromosomes found in metaphase, the highly condensed chromosomes with lengths shorter than that of interphase chromosomes and diameters of 1400 nm due to the folding of the radial loop domains as well as the further folding of the protein scaffold these loop domains are attached to in these highly condensed chromosomes, such as metaphase chromosomes THE RADIAL LOOPS ARE HIGHYL COMPACTED these radial loops also remain anchored to a scaffold, which is formed from the NONHISTONE PROTEINS OF THE NUCLEAR MATRIX these radial loops of the metaphase chromosomes or general highly compacted chromosomes are highly compacted and condensed, and these highly compacted and condensed metaphase chromosomes remain attached and anchored to A SCAFFOLD a SCAFFOLD is what these highly compacted and highly condensed radial loops are attached to, remain attached to and anchored to in highly compacted chromosomes such as metaphase chromosomes a SCAFFOLD Is formed from NONHISTONE PROTEINS OF THE NUCLEAR MATRIX a scaffold is formed from nonhistone proteins of the nuclear matrix a scaffold is formed from the nonhistone proteins of the nuclear matrix looking at a human metaphase chromosome in this condition, of a human metaphase chromosome, a highly compacted chromosome, the radial loops of DNA are in a VERY COMPACT CONFIGURATION the radial loops of DNA within a metaphase chromosome are in a VERY COMPACT CONFIGURATION if the chromosome is treated with a high concentration of salt in order to remove the core and linker histones, the core histones composing the histone octamers (2 copies each of H2A, H2B, H3, and H4) and the linker histone H1 protein, the HIGHLY COMPACT CONFIGURATION IS LOST however though the highly compact configuration of the chromosomal dna is lost due to the introduction of a high concentration of salt in order to remove the core histones and linker histones creating and linking nucleosomes, the BOTTOM OF THE ELONGATED RADIAL LOOPS REMAIN ATTACHED TO THE SCAFFOLD COMPOSED OF NONHISTONE PROTEINS when a high concentration of salt is added to the chromosomes in order to treat these metaphase chromosomes and removes the core histones and linker histones, the highly compact configuration of the metaphase chromosomes is lost, the metaphase chromosomes due to the introduction of a high concentration of salt that removes the core histones (the histone octamers composed of 2 copies each of H2A, H2B, H3, and H4 that the DNA wraps itself around, a DNA of a length of 146-147. base pairs) and the linker histones (responsible for linking the nucleosomes and the DNA wrapped around them together) while the highly compacted conformation of the metaphase chromosomes is lost, the elongated loops REMAIN ATACHED TO THE SCAFFOLD COMPOSED OF NONHISTONE PROTEINS the radial loops the elongated radial loops remain attached to the scaffold composed of nonhistone proteins recall that the scaffold that the radial loops, the elongated radial loops of the metaphase chromosomes are still attached to is composed of NONHISTONE PROTEINS looking at figure 10.22b, there is an arrow POINTING TO AN ELONGATED DNA STRAND this elongated dna strand is emanating from the DARKLY STAINING SCAFFOLD there is an elongated DNA strand emanating from the darkly staining scaffold THERE IS AN ELONGATED DNA strand emanating from the darkly staining scaffold that the radial loop, that the elongated radial loop dna remains attached to is shown in this figure, the elongated dna radial loop emanating from the darkly staining scaffold THE SCAFFOLD that the elongated DNA is attached to RETAINS THE SHAPE OF THE ORIGINAL METAPHASE CHROMOSOME even though the DNA strands have been greatly elongated though the DNA strands have been greatly elongated, the staining scaffold maintains the shape of the original metaphase chromosomes, the original conformation of the metaphase chromosomes, despite the elongation of the DNA that should in theory cause visible decor-action these results, of the elongated dna emanating from the staining scaffold as well as the staining scaffold maintaining the shape of the original metaphase chromosomes despite the elongation of the DNA strands showcases an important discovery these results of this particular conformation of the metaphase chromosomes being maintained by the staining scaffold as well as the elongated dna (purportedly, probably elongated radial loop of dna) emanating from the staining scaffold showcases and illustrates that the STRUCTURE OF METAPHASE CHROMOSOMES IS DETERMINED BY THE NUCLEAR MATRIX PROTEINS the nuclear matrix proteins are responsible for influencing, changing, and maintaining the structure of metaphase chromosomes the NUCLEAR MATRIX PROTEINS THE DETERMINANTS AND INFLUENCERS of the structure of metaphase chromosomes are the components of the scaffold that the radial loop domains remain attached to despite the addition of a high concentration of salt that removes the core histones, the core histones composing an octamer of 8 proteins, 2 copies of H2A, H2B, H3 and H4) and the linker histone, H1, which is responsible for connecting the nucleosomes together with the linker region that adds up to a single nucleosome containing a DNA sequence that is about 200 base pairs in length the nuclear matrix proteins are the components of the scaffold that these radial loop domains remain attached to, and these nuclear matrix proteins determine, change, alter, and maintain the structure of metaphase chromosomes the structure of the metaphase chromosomes is also heavily influenced by, changed, and maintained by histones, which are the proteins required to compact the radial loops (the DNA wraps around histone octamers, cluster of 8 histone proteins, 2 copies each of H2A, H2B, H3 and H4)

hydridization

when two distinct individuals with different characteristics (morphological, physiological, and/or behavioral) are mated/crossed with one another, that is known as hybridization the offspring of this union bw two distinct individuals with differing characteristics are known as hybrids a hybridization experiment example is a cross bw a purple flowered plant and a white flowered plant, differing in their flower color Mendel, when conducting his hybridization experiments, was very intrigued by the consistency of offspring showcasing the traits of their parents (possibly both or simply one of them) he discovered that the governing principles of whether or not an offspring would showcase a parental trait was rooted in natural mathematical laws (that would determine the probability of the offspring showcasing particular traits possessed by their parents) in order to prove this hypothesis of mathematical laws governing these natural processes of reproduction, he needed to implement quantitative experiments, recording the numbers of offspring produced from certain couplings, and the traits they all expressed (for example how many of the offspring expressed say a purple flower color, as looking at the numbers would result in progress towards the establishment of mathematical probability of inheriting and showcasing a parental trait) the garden pea is the subject he chose- Pisum sativum he wanted to discover what natural laws govern the reproduction of plant hybrids why did he use the garden pea specifically? - the species was available in several varieties, so they all belonged to the same species and could reproduce with one another, but also while belonging to the same species, had established differences in their traits, so a hybridization experiment could be conducted the variations occurred in height, flowers, seeds, and pods

monohybrid cross/single-factor cross

where the experimenter is only looking at one character (one trait of an organism, and crossing the two variants found within that character amongst the organisms) the offspring of a monohybrid/single-factor cross are single-character hybrids another term for the offspring of a monohybrid/single factor cross is monohybrid, a hybrid of the variants of one characteristic being crossed with one another

aneuploidy and abnormal phenotypes

why are geneticists so interested in aneuploidy? why are geneticists so interested in aneuploidy geneticists are so interested in aneuploidy due to the relationship of aneuploidy to certain particular inherited disorders within humans geneticists are so interested in aneuploidy due to the relationship bw aneuploidy and particular inherited disorders within humans the majority of individuals are born with a normal number of chromosomes the majority of individuals within the human species are born with a normal number of chromosomes, 46 chromosomes, 2 sets of 23 chromosomes each, one set inherited maternally, the other set inherited paternally however, although the majority of individuals within the human population are born with a normal and typical number of chromosomes, 46 chromosomes, alterations in chromosome number do occur fairly frequently during gamete formation alterations in chromosome number do occur frequently during gamete formation ABOUT 5 to 10 PERCENT Of all fertilized human eggs result in an embryo with an abnormality in chromosome number about 5 to 10 percent of all fertilized human eggs result in an embryo with an abnormality in chromosome number about 5 to 10 percent of all fertilized human eggs result in an embryo with an abnormality in chromosome number about 5 to 10 percent of all fertilized human eggs result in an embryo with an abnormality in chromosome number about 5 to 10 percent of all fertilized human eggs result in an embryo with an abnormality in chromosome number in the majority of cases these abnormal embryos with an abnormality in chromosome number, recall that 5 to 10 percent of fertilized eggs result in an embryo with an abnormality in chromosome number 5 to 10 percent of fertilized eggs result in an embryo with an abnormality in chromosome number, and these embryos with an abnormality in chromosome number tendon to develop properly these embryos tend to not develop properly and result in a spontaneous abortion v early in pregnancy these embryos tend to not develop properly and result in a spontaneous abortion v early in pregnancy approximately 50 percent of spontaneous abortions are due to an abnormality in chromosomes number of these developing embryos that do not properly develop and then result in a spontaneous abortion there are some cases where an abnormality in chromosome number produces an offspring that survives to birth or longer there are some cases where an abnormality in chromosome number produces an offspring that survives to birth or longer several human disorders, disorders in the human population, involve abnormalities in chromosomal number these individuals with abnormalities in chromosomal number develop as embryos despite the abnormality in chromosome number and are born and live past birth, but they are phenotypically affected by the abnormality in chromosome number the most common abnormalities in chromosome number are TRISOMIES OF CHROMOSOME 13, 18, or 21 the most common abnormalities in chromosome number that occur within the human population are trisomies of chromosome 13, 18, or 21 abnormality in the number of sex chromosomes are also fairly common the most common abnormalities in chromosome number occur in trisomy of chromosome 13, 18, or 21, and chromosomal abnormality in sex chromosomes most of the known trisomies of chromosomal number abnormality, most of the known trisomies of these category occur in small chromosomes such as 13, 18, and 21, chromosomes that carry fewer genes compared to larger chromosomes trisomies of the other human autosomes (chromosomes 1-21 other than 13, 18, and 21) and monosomes of all of the autosomes, chromosomes 1-21 are presumed to produced a lethal phenotype trisomies in autosomes other than chromosomes 13, 18, and 21, small chromosomes with generally fewer genes than larger chromosomes, and monosomies in any autosomes are presumed to result in a lethal phenotype, and these chromosomal number alterations, trisomies in chromosomes other than 13, 18, and 21, and monosomes in any of the autosomes have been found in developing embryos that spontaneously aborted, these types of chromosomal number alteration, trisomy in chromosomes other than 13, 18, and 21, and monosomy in any of the autosomes have been found in spontaneously aborted embryos and fetuses an example of this, all possible human trisomies have been found in spontaneously aborted embryos except trisomy 1, indicating the the majority of trisomies, particular trisomies outside of chromosome 13, 18, and 21, which have been seen in developed embryos and born fetuses, are lethal it is presumed about trisomy 1, due to the fact that it is the only trisomy that has not been found in spontaneously aborted embryos, it is believed that trisomy 1, trisomy of chromosome 1 is lethal at such an early stage, that it prevents the successful implantation of the fertilized egg, of the embryo on the uterus the trisomy of chromosome 1 is presumed to be lethal at such an early stage that an embryo with trisomy 1 will not be allowed to implant itself in the lining of the uterus VARIATION IN THE NUMBER OF X chromosomes unlike that of other large chromosomes, is often NONLETHAL variation in the number of X chromosomes, unlike the variation in other large chromosomes, tends to be nonlethal the survival of trisomy X individuals may be explained by the process of X inactivation, where there tend to be two X chromosomes in every somatic cell of the developed individual that are inactivated, in order to balance out gene expression and insure there isn't excess gene product in an individual that contains more than one X chromosome, all additional x chromosomes are converted to Barr bodies in the somatic cells of adult tissues in an individual with more than one x chromosome, all of the additional X chromosomes are converted to Barr bodies in the somatic cells of adult tissues, all of the additional x chromosomes are converted to Barr bodies in the somatic cells of adult tissues in an individual with trisomy x, with three X chromosomes, two of the three of these x chromosomes are converted into Barr bodies within the somatic cells of the adult tissues of this trisomy x individual unlike the level of expression for autosomal genes, the normal level of expression for x linked genes is from a single x chromosome, due to x inactivation of any chromosome that exceeds one chromosome the normal level of gene expression for x linked genes is from a single x chromosome the normal level of gene expression for x linked genes is from a single x chromosome that is where the normal level of gene expression comes from, from a single X chromosome due to the creation of a Barr body, the X chromosome inactivation that occurs the X chromosome inactivation that occurs in all somatic cells containing more than one X chromosome causes the level of gene expression of x linked genes to always be connected t and influenced by a single x chromosome in other words in regards to the level of gene expression of x linked genes, the CORRECT LEVEL OF MAMMALIAN GENE EXPRESSION results from two copies of each autosomal gene and one copy of each x linked gene the correct level of mammalian gene expression, gene expression in mammals designates two copies of each autosomal gene, and one copy of each x linked gene the correct level of mammalian gene expression, the correct level of gene expression in mammals designated two copies of each autosomal gene, and one copy of each x linked gene the correct level of mammalian gene expression, the correct level of gene expression in mammals designates two copies of each autosomal gene and one copy of each x linked gene the correct level of mammalian gene expression, the correct level of gene expression (due to the phenomenon of X inactivation and the creation of compacted, transcriptionally inactive Barr bodies when there is more than one X chromosome present) is two copies of each autosomal gene, and one copy of each x-linked gene this explains how the expression of x linked genes in males, who contain only one x chromosome in an allosomal sex chromosome combination of XY can be maintained at the same level as the gene expression of x-linked genes in females with the allosomal sex chromosome combination of XX, the same level of gene expression of x linked genes can be maintained in both males with the allosomal sex chromosome combination XY, and females with the allosomal sex chromosome combination XX, due to X chromosome inactivation, the conversion of excess x chromosomes, X chromosomes other than the one to compacted, transcriptionally inactive Barr bodies the correct level of mammalian gene expression, the correct level of gene expression in mammals being designated as two copies of all autosomal genes within the mammalian genome and one copy of all x linked genes, may also explain why trisomy x is not a lethal condition, due to the X inactivation of the 2 additional chromosomes present in the genome of the individual with the trisomy x condition

Drosophila wild type and mutant alleles

wild type dominant alleles: red eyes and normal wings mutant recessive alleles: white eyes and miniature

non-Mendelian inheritance patterns due to genes not within the nucleus

within eukaryotic species, there is the phenomenon of extranuclear inheritance the most biologically important process of extranuclear inheritance is due to the genetic material found within cellular organelles, namely, mitochondria and chloroplasts

mitochondrial and chloroplast patterns of inheritance

within heterogamous species, there are two kinds of haploid gametes that are made the female gamete (the gamete produced by a female) tends to be large, and is the majority provider of the cytoplasm to the zygote when it is formed the male gamete (the gamete produced by a male) tends to be small, and oftentimes provides only the nucleus to the zygote and nothing more than that (certainly not a lot, if any cytoplasm) therefore, it has been determined that mitochondria and chloroplasts are maternally inherited the majority of the time, due to the large size of the female gamete contributing to the creation of the zygote, as well as the fact that it provides the majority of the cytoplasm when the zygote is formed this is not always the case in mammals, the organelle is mitochondria, an the transmission of genetic material of mitochondria is maternal inheritance in S. cerevisiae, the organelle is mitochondria, and the transmission of mitochondrial genetic material is biparental inheritance in molds, the organelle is mitochondria, and the transmission of mitochondrial genetic material is usually maternal inheritance, though the phenomenon of paternal inheritance has been found in the genus allomyces in chlamydomonas, the organelle is mitochondria, and the transmission of the mitochondrial genetic material is that it is inherited from the parent with the mt- mating type in chlamydomonas, the organelle is chloroplast, and the transmission of the chloroplast genetic material is that it is inherited from the parent with the mt+ mating type in plants, particularly angiosperms, the organelles are mitochondria and chloroplasts, and the transmission of the mitochondrial and chloroplast genetic material is oftentimes maternal inheritance, though biparental inheritance has been found amongst some species in plants, particularly gymnosperrms, the organelles are mitochondria and chloroplasts, and the transmission of the mitochondrial and chloroplast genetic material is usually paternal inheritance there is the concept of paternal leakage, where within a species that usually transmits genetic material via the phenomenon of maternal inheritance, the paternal parent can occasionally provide mitochondria through their gametes, sperm the phenomenon of paternal leakage occurs in a multitude of species that mainly exhibit their organelles being maternally inherited the species where paternal leakage occurs are usually species where organelles are inherited through the phenomenon of maternal inheritance an example of a species where paternal leakage occurs: the mouse there are approximately 1-4 paternal mitochondria inherited for every 100,000 maternal mitochondria inherited per generation of offspring so for every 100,000 mitochondria that are maternally inherited, there are 1-4 paternal mitochondria inherited, exhibiting the phenomenon of maternal inheritance and the appearance of paternal leakage the majority of offspring do not paternally inherit any mitochondria however, there is the possibility of a rare individual that does indeed inherit a mitochondrion, or mitochondria paternally, from the sperm provided by the father

Boris Ephrussi experimentation with petite mutants

yeast cells are designated as two types, a and alpha Boris Ephrussi was able to cross a wild type strain to his petite mutants (the yeast cells with a low and slow proliferation rate) the genetic analyses that he implemented showcased the fact that petite mutants can be inherited in a variety of ways when Ephrussi crossed a wild type strain to a segregational petite mutant, he found a ratio amongst the offspring of this cross of 2 wild type cells to 2 petite cells the ratio found in the offspring of this cross is consistent with patterns of Mendelian inheritance (we will cover the concept of tetrad analysis in Ch.6) due to this observed ratio from this cross, both of which followed classic and established Mendelian patterns of inheritance, it was determined that segregational petite mutations cause defects within genes found within the cell nucleus (the segregational petite mutations cause these genes found within the cell nucleus to be nonfunctional) the genes that these segregational petite mutations render nonfunctional are genes that code for the gene products of proteins necessary for the function of mitochondria these proteins coded for by genes in the nucleus (that are no longer produced when segregational petite mutants come into play and make the genes in the nucleus coding for these proteins nonfunctional, therefore resulting in the proteins coded for by these genes not being produced) are synthesized within the cytosol (recall that they are coded for by genes within the nucleus, but synthesized within the cytosol) these proteins are then taken up the mitochondria, and then these proteins perform their functions within this organelle why are segregational petites designated as such? they are designated as such because these segregational petits segregate in a manner that follows Mendelian patterns of inheritance (and the established law of segregation) during the formation of gametes (meiosis) there is a second category of petite mutants these petite mutants are designated as vegetative petite mutants these vegetative petite mutants, unlike the segregational petite mutants, do not segregate during gametogenesis in a Mendelian manner Boris Ephrussi discovered two types of vegetative petites: - neutral petites - suppressive petites when Ephrussi crossed a wild-type strain and a natural petite, all four haploid daughter cells were wild type (meaning that in each haploid daughter cell, the wild type won out) this inheritance pattern of all 4 haploid daughter cells from this cross showcasing the wild type deviates from the expected Mendelian ratio of 2:2, due to the law of segregation that details the separation of alleles into individual gametes when Boris Ephrussi implemented a cross bw a wild type strain and a suppressive petit, the only yield was of petite colonies therefore Euphressi determined that both kinds of vegetative petites are defective in regards to mitochondrial function (they both cause mitochondria to be nonfunctional, and that results in the slow proliferation of new cells), and both kinds of vegetative petites also showcase a non-Mendelian pattern of inheritance, are inherited in ways that do not align with established Mendelian law the results that Euphressi found occurred due to the fact that vegetative petites carry mutations within the mitochondrial genome itself (and the phenotypes possibly have to do with mitochondrial inheritance) since the initial studies implemented by Euphressi, researchers now understand that neutral petites lack the majority of their mitochondrial DNA in contrast to this, suppressive petites usually only lack small segments and portions of their mitochondrial DNA this has to do with the phenotypes that yeast cell offspring/daughter cells inherit when two yeast cells are mated to one another, the resulting daughter cell receives mitochondria from both parents an example of a cross: a cross bw a wild type and a neutral petite strain results in haploid daughter cells that all present as wild type due to the fact that a neutral petite strain lacks the majority of its mitochondrial DNA, and therefore will not pass much onto its daughter cells, and therefore not have any affect on the phenotype influenced by the mitochondrial genotype the wild type strain will have intact and a full amount of mitochondrial DNA, and will pass it onto its offspring, solely influencing the offspring's phenotype based on its mitochondrial genotype