Genetics Final
4.5 Predict the outcome of crosses for X-linked inheritance
In mammals, females are XX and males are XY X-linked inheritance: an inheritance pattern in certain species that involves genes that are located only on the X chromosome Males transmit X-linked genes only to their daughters and sons receive their X-linked genes from their mothers Hemizygous: indicates that a male has a single copy of an X-linked gene A male mammal is said to be hemizygous for X-linked genes Because males of certain species, such as humans, have a single X chromosome, another distinctive feature of X-linked inheritance is that males are more likely to be affected by rare, recessive X-linked disorders Reciprocal crosses: a pair of crosses in which the traits of the two parents differ with regard to sex For example, one cross could be a red-eyed female fly and a white-eyed male fly and the reciprocal cross would be a red-eyed male fly and a white-eyed female fly By comparing the two punnett squares, we see that the outcome of the reciprocal cross yielded different results This is expected with X-linked genes because the male transmits the gene only to female offspring but the female transmits an X chromosome to both male and female offspring Because the male parent does not transmit the X chromosome to his sons, he does not contribute to their X-linked phenotypes This explains why X-linked traits do not behave the same way in reciprocal crosses Experimentally, the observation that reciprocal crosses do not yield the same results is an important clue that a trait may be X-linked
Explain how the distance between linked genes affects the proportions of recombinant and nonrecombinant offspring
In the experiment, Morgan also noticed a quantitative difference between recombinant offspring involving body color and eye color versus those involving eye color and wing length He found a substantial difference between the numbers of recombinant offspring when pairs of genes were considered separately Recombinant patterns involving only eye color and wing length were fairly common Another proposal that he made was that the likelihood of crossing over depends on the distance between two genes If two genes are far apart from each other, crossing over is more likely to occur between them than it is between two genes that are close together
Predict the outcome of dihybrid crosses using a Punnett square
In this two-factor cross, we need to make a punnett square containing 16 boxes The phenotypes of the resulting offspring are predicted to occur in a ratio of 9:3:3:1
Explain the underlying molecular mechanisms of incomplete dominance and codominance
Incomplete dominance: At the molecular level, the alleles that causes a white phenotype is expected to result in a lack of a functional protein required for pigmentation Depending on the effects of gene regulation, the heterozygotes may produce only 50% of the normal protein but this amount is not sufficient to produce the same phenotype as the C^RC^R homozygote which may take twice as much of this protein Conclusions about dominance may depend on the level of examination Our opinion of whether a trait is dominant or incompletely dominant may depend on how closely we examine the trait in the individual The more closely we look the more likely we are to discover that the heterozygote is not quite the same as the wild-type homozygote
4.4 Predict the outcome of crosses involving incomplete dominance and codominance
Incomplete dominance: a pattern of inheritance in which a heterozygote that carries two different alleles exhibits a phenotype that is intermediate to those of the corresponding homozygous individuals EX: a heterozygote may have pink flowers, whereas the homozygotes have red or white flowers Four-o'clock plant The punnett square ratio in the F2 generation displated a 1:2:1 phenotypic ratio, which is different from the 3:1 ratio observed for simple Mendelian inheritance The ABO group of antigens, which determine blood type in humans are produced in the human population under the control of multiple alleles Two of these alleles exhibit a relationship called codominance Codominance: the phenomenon in which two allele are both expressed in the heterozygous individual For example, a person with the genotype I^AI^B has the blood type AB and expresses both surface antigens A and B
Explain how small effector molecules affect the function of activators and repressors
Increase transcription 1. Inducers function in two ways A. Bind activators and cause them to bind to DNA B. Bind repressors and prevent them from binding to DNA Genes that are regulated in this manner are termed inducible Inhibit transcription 1. Corepressors bind to repressors and cause them to bind to DNA 2. Inhibitors bind to activators and prevent them from binding to DNA Genes that are regulated in this manner are termed repressible
A diploid organism has a total of 36 chromosomes. Assuming all possible chromosome combinations are viable, if a mutant tetraploid version of this organism was created how many chromosomes would it have? If a mutant version of the diploid organisms was monosomic for chromosome 9 how many chromosomes would it have?
72; 35 2n = 36 → n= 18 4n = 36 → n = 72 36 - 1 = 35
8.1 Describe the characteristics that are used to classify and identify chromosomes
8.1: to identify changes in chromosome structure and number, researchers need to start with a reference point: the chromosomal composition of most members of a given species Ex: most people have two sets of chromosomes with 23 specific chromosomes in each set, resulting in a total of 46 chromosomes On rare occasion, a person may have a chromosomal composition different from that of most other people- such as person may have a chromosome that has an unusual structure or may have too few or too many chromosomes Cytogeneticists- scientists who study chromosomes microscopically- examine the chromosomes from many members of a given species to determine the common chromosomal composition and to identify rare individuals that show variation in chromosome structure and/or number
Apply a Chi square analysis to distinguish between linkage and independent assortment
A chi square test can be employed to determine if the outcome of a two-factor cross is consistent with linkage or independent assortment To conduct a chi-square test, we must first propose a hypothesis For a two-factor cross, the standard hypothesis is chosen even if the observed data suggest linkage, because an independent assortment hypothesis allows us to calculate the expected number of offspring based on the genotypes of the parents and the law of independent assortment In contrast, for two linked genes that have not been previously mapped, we cannot calculate the expected number of offspring from a genetic cross because we do not know how likely it is for a crossover to occur between the two genes Without expected number of recombinant and nonrecombinant offspring, we cannot conduct a chi square test Therefore, we begin with the hypothesis that the genes are not linked The hypothesis that we are testing is called the null hypothesis (a hypothesis that assumes there is no real difference between the observed and expected values) The goal is to determine whether or not the data fit the hypothesis If the chi square value is low and we cannot reject the null hypothesis, we infer that the genes assort independently On the other hand, if the chi square value is so high that our hypothesis is rejected, we accept the alternative hypothesis, namely, that the genes are linked
8.6 Explain why aneuploidy usually has a detrimental effect on phenotype and give examples in humans
A key reason why geneticist are so interested in aneuploidy is its relationship to certain inherited disorders in humans Even though most people are born with 46 chromosomes, alterations in chromosome number occur fairly frequently during gamete formation About 5% - 10% of all fertilized human eggs result in an embryo with an abnormality in chromosome number In most cases, such an embryo does not develop properly and a spontaneous abortion occurs very early in pregnancy Approximately 50% of all spontaneous abortions are due to alterations in chromosome number Most common are trisomies of chromosome 13, 18, or 21 and abnormalities in the number of the sex chromosomes Trisomies of the other human autosomes and monosomies of all autosomes are presumed to produce a lethal phenotype and many have been found in spontaneously aborted embryos and fetuses
10.1 & 10.3 Compare and contrast organization of sites along Prokaryote and Eukaryote chromosomes, i.e. how do prokaryotic and eukaryotic chromosomes differ and how are they similar.
A typical bacterial chromosome is a few million base pairs (bp) in length Commonly has a few thousand different genes which are interspersed throughout the entire chromosome Protein-encoding genes: genes that produce mRNA and encode polypeptides account for majority of bacterial DNA The non transcribed regions of DNA located between adjacent genes are called intergenic regions: in a chromosome, a region of DNA that lies between two adjacent genes Have one origin of replication: a site on a chromosome that functions as an initiation site for the assembly of several proteins that begin the process of DNA replication Repetitive sequences: short DNA sequences that occur many times within a species' genome Nucleoid: a darkly staining region that contains the genetic material of mitochondria, chloroplasts or bacteria Depending on growth conditions and phase of cell cycle, bacteria may have one to four identical chromosomes per cell The number of copies varies depending on the bacterial species Each chromosome is found within its own distinct nucleoid in the cell Unlike the eukaryotic nucleus, the bacterial nucleoid is not a separate cellular compartment surrounded by a membrane The DNA in a nucleoid is in direct contact with the cytoplasm of the cell Eukaryotic species have one or more sets of chromosomes in the cell nucleus- each set is composed of several different linear chromosomes Each eukaryotic chromosome contains a long, linear DNA molecule that is typically tens of millions to hundreds of millions of base pairs in length A single chromosome usually has a few hundred to several thousand different genes A typical eukaryotic gene is several thousand to tens of thousands of base pairs in length In less complex eukaryotes such as yeast, genes are relatively small, often several hundred to a few thousand base pairs long In more complex eukaryotes, such as mammals and flowering plants, protein-encoding genes tend to be much longer due to the presence of introns: non coding intervening sequences Exons: regions of an RNA molecule that remain after splicing has removed the introns The size of introns ranges from less than 100 bp to more than 10,000 bp- therefore, the presence of large introns can greatly increase the lengths of eukaryotic genes Eukaryotic chromosomes contain many origins, interspersed approximately every 100,000 bp Centromere: a segment of a eukaryotic chromosome that provides an attachment site for the kinetochore Each chromosome contains a single centromere, which usually appears as a constricted region of a mitotic chromosome Kinetochore: composed of a group of proteins that link the centromere to the spindle apparatus during mitosis and meiosis, ensuring the proper segregation of the chromosomes to each daughter cell The ends of linear eukaryotic chromosomes have specialized regions known as telomeres that serve several important functions in the replication and stability of a chromosome Prevent chromosomal rearrangements such as translocations Prevent chromosome shortening in two ways First, they protect chromosomes from digestion via enzymes called exonucleases that recognize the ends of DNA An unusual form of DNA replication occurs at the telomere to ensure that eukaryotic chromosomes do not become shortened with each round of DNA replication
Compare the benefits and limitations of using model organisms to study eukaryotic gene function.
A very broad learning outcome illustrated by discussions related to the following: defining the information storage molecule, DNA replication, transcription, genetic linkage and classic Mendelian genetics. Focus your attention to Pisum sativum, Mus musculus, Drosophila melanogaster, Neurospora crassa, Escherichia coli, Streptococcus pneumoniae. You do not need to go through each one of these model organisms and list benefits and limitations, but rather think about the common benefits and limitations between them all.
Your muscle cells, nerve cells, and skin cells have different functions because each kind of cell
Activates different genes
Outline how alternative splicing occurs, and describe its benefits
Alternative splicing regulates which exons occur in a mature mRNA, allowing different polypeptides to be made from the same gene Alternative splicing: the phenomenon that a pre-mRNA can be splices in more than one way Why is it advantageous? Alternative splicing produces two or more polypeptides from the same gene that have differences in their amino acid sequences, leading to possible changes in their functions In most cases, the alternative versions of the protein have similar functions, because most of their amino acid sequences are identical to each other Alternative splicing produces differences in amino acid sequences that provide each polypeptide with its own unique characteristics Since it allows two or more different polypeptide sequences to be derives from a single gene, some geneticists have speculated that an important advantage of this process is that it allows an organism to carry fewer genes in its genome
Predict the outcome of monohybrid crosses using a Punnett square
An easy way to predict the outcome of simple genetic crosses and self-fertilization experiment is to use a punnett square We expect 3:1 ratio for a monohybrid cross between the dominant and recessive trait
11.1 Relate how Meselson and Stahl were able to demonstrate semiconservative model of replication
As seen in the data, after one round of DNA replication (after one generation) all of the DNA sedimented at a density that was half-heavy Both the semiconservative and dispersive models are consistent In contrast, the conservative model predicts two separate DNA types: A light type A heavy type Because all of the DNA had sedimented as a single band, this model was disproved According to the semiconservative model, the replicated DNA would contain one original strand (a heavy strand) and a newly made daughter strand (a light strand) After approximately two rounds of DNA replication (after 1.9 generations), a mixture of light DNA and half-heavy DNA was observed This result was consistent with the semiconservative model of DNA replication because some DNA molecules should contain all light DNA and other molecules should be half-heavy The dispersive model predicts that after two generations, the heavy nitrogen would be evenly dispersed among four strands This result was not obtained- instead, the results provided compelling evidence in favor of only the semiconservative model
27.6 Define assortative mating, inbreeding, and outbreeding
Assortative mating: sexual reproduction in which individuals preferentially breed with each after based on their phenotypes Outbreeding: sexual reproduction between genetically unrelated individuals In the absence of other evolutionary processes, inbreeding and outbreeding do not affect allele frequencies in a population However, they do alter the relative proportions of homozygotes and heterozygotes that are predicted by the Hardy-Weinberg equation Inbreeding: sexual reproduction between two genetically related individuals Inbreeding involves a smaller gene pool because the reproducing individuals are related genetically Inbreeding coefficient (F): the probability that two alleles for a given gene in a particular individual will be identical because both copies are due to descent from a common ancestor An inbreeding path for an individual is the shortest path through the pedigree that includes both parents and the common ancestors
Huntington disease is a rare (not homozygous dominant) neurodegenerative human disease determined by a dominant allele, HD. The disorder is typically a late onset disease with symptoms appearing after the age of 30. A young man has learned that his father has developed the disease. What is the probability that the young man will also develop the disease? What is the probability that a child of the young man carries the HD allele?
Assume mother is unaffected with genotype of homozygous recessive ½ (do punnett square of heterozygous mating with homozygous recessive) Take two probabilities and multiply them The father has to have gotten than allele (½) Probability of passing the allele onto that child (½) = ¼ Hh (affected father) x hh (affected mother)
12.2 Explain how RNA polymerase transcribes a bacterial gene, i.e. directionality, what parts of the gene are transcribed, compared to Eukaryotes.
Bacterial transcription is initiated when RNA polymerase holoenzyme binds at a promoter The sigma factor subunit of RNA polymerase holoenzyme recognizes the -35 and -10 sequences of the promoter The DNA unwinds at the -10 sequence to form an open complex and a short RNA is made Then sigma factor dissociates from the holoenzyme and RNA polymerase core enzyme proceeds down the DNA synthesizing RNA and forming an open complex as it goes
Sometimes a trait seems to disappear in a family and then reappear in later generations. If neither parent has the trait, but some of the offspring do, what would you conclude about the inheritance of the trait?
Both parents are carriers of the recessive form of the gene
Red-green color blindness in humans is an X-linked recessive trait. What will the progeny phenotypic ratios be if a carrier female is mated with an unaffected male?
C= affected c = unaffected Male = XCY ¼ unaffected males ¼ affected males
Use the Hardy-Weinberg equation to calculate allele and genotype frequencies
Calculations of two fundamental values are central to population genetics: Allele frequencies: the number of copies of a particular allele in a population divided by the total number of alleles for that gene in the population Allele frequency= number of copies of a specific allele in a population / total number of all types of alleles for that gene in a population For calculating allele frequency, homozygous individuals have two copies of an allele, whereas heterozygotes have only one Genotype frequencies: the number of individuals with a particular genotype in a population divided by the total number of individuals in the population Genotype frequency= number of individuals with a particular genotype in a population / total number of individuals in a population Allele and genotype frequencies are always less than or equal to 1 (less than or equal to 100%) If a gene is monomorphic, the allele frequency for the single allele will be equal to or slightly less than a value of 1.0 For polymorphic genes, if we add up the frequencies for all of the alleles in the population, we should obtain a value of 1.0
Explain how population size affects genetic drift
Changes in population size may influence genetic drift via the bottleneck effect Bottleneck effect: a mechanism that can give rise to genetic drift- occurs when most members of a population are eliminated without any regard to their genetic composition Founder effect: a change in allele frequency that occurs when a small group of individuals separates from a larger population and establishes a colony in a new location
Distinguish between chemical and physical mutagens and provide examples
Chemical: Nitrous acid Nitrogen mustard Ethyl methanesulfonate Proflavin 5-Bromouracil 2-Aminopurine Physical: X-rays UV light
10.5 Define chromatin, heterochromatin and euchromatin and identify impact of condensation on gene expression
Chromatin: the complex of DNA and proteins that is found within eukaryotic chromosomes Heterochromatin: during interphase, highly compacted regions of chromosomes in which the DNA is usually transcriptionally inactive Euchromatin: less compacted regions of chromosomes, where DNA may be transcriptionally active The condensation process generally involves a closer association of loop domains with each other, and also a closer association between adjacent nucleosomes This additional level of compaction greatly shortens the overall length of a chromosome and produces a diameter of approximately 700 nm
11.1 Describe the structural features of DNA that enable it to be replicated
Complementarity of the two strands of a double helix - based on AT/GC rule Antiparallel nature of the two strands of a double helix - directionality and 5' - 3' vs 3' - 5'
Compare and contrast the structure of nucleotides found in DNA & RNA
DNA contains deoxyribose as its sugar and the bases A, T, G and C RNA contains ribose as its sugar and the bases A, U, G, and C In a DNA or RNA strand, the oxygen on the 3' carbon of the sugar is linked to the phosphorus atom of the phosphate in the adjacent nucleotide The two atoms (O and H) are found within individual nucleotides but not when nucleotides are joined together to make strands of DNA and RNA
Recall what DNA is, does and how it is structured within the cell.
DNA: deoxyribonucleic acid and composes genetic material and is a component of chromosomes Each chromosome contains hundreds to thousands of shorter segments that function as genes
8.2 Compare and contrast the four types of changes in chromosome structure
Deletion: a segment of chromosomal DNA is missing- the affected chromosome is deficient in a significant amount of genetic material Deficiency: condition in which a segment of chromosomal material is missing in a region Duplication: the repetition of a segment of DNA more than once within a chromosome and/or within a genome Inversion: a change in the orientation of genetic material along a chromosome such that a segment is flipped or reversed from the normal order- a change in the direction of the genetic material along a single chromosome EX: a segment of one chromosome has been inverted, so the order of four G bands is opposite to what it was originally Translocation: rearrangement in which one segment of a chromosome breaks off and becomes attached to a different chromosome or a different part of the same chromosome Simple translocation: rearrangement in which one piece of a chromosome becomes attached to a different chromosome Reciprocal translocation: rearrangement in which two different chromosomes exchange pieces- which alters both of them
Outline how mutations arise by depurination, deamination and tautomeric shifts
Depurination: the most common type of chemical change that occurs naturally- involves the removal of a purine (adenine or guanine) from the DNA The covalent bond between deoxyribose and a purine base is somewhat unstable and occasionally undergoes a spontaneous reaction with water that releases the base from the sugar, thereby creating an apurinic site (a site in DNA that is missing a purine base) In a typical mammalian cell, approximately 10,000 purines are lost from the DNA in a 24-hour period at 37 degrees celsius The rate of loss is higher if the DNA is exposed to agents that cause certain types of base modifications such as the attachment of alkyl groups (methyl or ethyl groups) If the repair system fails, however, a mutation may result during subsequent rounds of DNA replication Deamination: A second spontaneous chemical change that may occur in DNA is the deamination (the removal of an amino group molecule- the removal of an amino group from cytosine produces uracil) of a cytosine base Deamination involves the removal of an amino group from the cytosine base- this produces uracil DNA repair enzymes can recognize uracil as an inappropriate base within DNA and subsequently remove it If such a repair does not take place, a mutation may result because uracil hydrogen bonds with adenine during DNA replication If a DNA template strand has a uracil instead of cytosine, a newly made strand will incorporate adenine instead of guanine Tautomeric shift: A third way that mutations may arise spontaneously involves a temporary change in base structure called a tautomeric shift (a temporary change in chemical structure, such as an alteration between the keto and enol forms of the bases that are found in DNA) The two forms in each of these pairs can interconvert by a chemical reaction that involves the migration of a hydrogen atom and a switch of a single bond and an adjacent double bond They cause mutations by the shift must occur immediately prior to DNA replication When DNA is double stranded, the base pairing usually holds the bases in their more stable forms- after the strands unwind, however, a tautomeric shift may occur
19.5 Compare and contrast Direct Repair, Base Excision & Nucleotide
Direct repair: an enzyme recognizes an incorrect alteration in DNA structure and directly converts the structure back to the correct form Base excision and nucleotide excision repair: an abnormal base or nucleotide is first recognized and removed from the DNA and a segment of DNA in this region is excised- then this complementary DNA strand is used as a template to synthesize a normal DNA strand
Compare and contrast directional, stabilizing, disruptive and balancing selection
Directional selection: natural selection that favors an extreme phenotype- this usually leads to the fixation of the favored allele Balancing selection: a pattern of natural selection that favors the maintenance of two or more alleles in a population It may be due to a heterozygote advantage or negative frequency-dependent selection Disruptive selection: natural selection that favors the maintenance of two or more alleles in heterogeneous environments, resulting in two or more phenotypes Stabilizing selection: natural selection that favors individuals with an intermediate phenotype
13.2 Outline how the information within mRNA is used to make a polypeptide
During translation, the codons in mRNA provide the information to make a polypeptide with a specific amino acid sequence The sequence of nucleotides within DNA is transcribed to make a complementary sequence of nucleotides within mRNA This sequence of nucleotides in mRNA is translated into a sequence of amino acids in a polypeptide tRNA molecules act as intermediates in this translation process The tRNAs are detached from the polypeptide, one at a time, as it is being synthesized- also, this gene does not contain any introns The ability of mRNA to be translated into a specific sequence of amino acids relies on the genetic code The sequence of bases within an mRNA molecule provides coded information that is read in groups of three nucleotides known as codons
Describe how alleles can exhibit incomplete penetrance and vary their expressivity
Environmental factors or effects of modifier genes (one or more genes effect the phenotype)
You are studying two traits under the control of two different genes that follow the rules of simple mendelian inheritance. The probability that the gametes of an individual heterozygous for both traits will only carry dominant alleles is
Equal to all other possible allelic combinations (¼)
Which statement below best describes the compaction level and thus transcriptional activity of heterochromatin and euchromatin?
Euchromatin is not as compact as heterochromatin and is transcriptionally active
8.5 Define euploidy and aneuploidy
Euploid: describes an organism in which the chromosome number is an exact multiple of a chromosome set Aneuploid: not euploid- refers to a variation in chromosome number such that the total number of chromosomes is not an exact multiple of a set (or of the number n)
6.2 Describe how crossing over can change the arrangements of alleles along a chromosome
Even when alleles for different genes are linked on the same chromosome, the linkage can be altered during meiosis In diploid eukaryotic species, homologous chromosomes can exchange pieces with each other Crossing over: a physical exchange of pieces between homologous chromosomes that most commonly occur during prophase of meiosis I The replicated chromosomes, known as sister chromatids, associate with the homologous sister chromatids to form a structure known as a bivalent Bivalent: a structure in which two pairs of homologous sister chromatids have synapse (aligned) with each other When crossing over occurs, the two lowermost haploid cells contain combinations of alleles, namely, B and a and in one or b and A in the other, which differ from those in the original chromosomes In these two cells, the grouping of linked alleles has changed The haploid cells carrying the B and a alleles or the b and A alleles are called recombinant cells If such haploid cells are gametes that participate in fertilization, the resulting offspring are called recombinant offspring These offspring can display combinations of traits that are different from those of either parent In contrast, offspring that have inherited chromosomes carrying the same combinations of alleles found in the chromosomes of their parents are known as nonrecombinant offspring When offspring inherit a combination of two or more alleles or traits that are different from either of their parents, this event is known as genetic recombination and occurs in two ways: When two or more genes are linked on the same chromosomes, crossing over during meiosis can result in genetic recombination When two or more genes are on different chromosomes, the independent assortment of those chromosomes during meiosis can result in genetic recombination
Which of the following statements concerning the inheritance of a dominant trait (complete penetrance) is true?
Every affected person must have at least one affected parent
Diagram how inversion heterozygotes produce abnormal chromosomes due to crossing over
Fig. 8.11
27.1 Define gene pool and population
Gene pool: all of the alleles of every gene within a particular population Population: a group of individuals of the same species that occupy the same region and can interbreed with one another
How is the expression of genes regulated or controlled?
Genes are turned on and off at appropriate times throughout one's life
Explain the function of the genetic code
Genetic code: the correspondence between a codon (a sequence of three bases in an mRNA molecule) and the functional role that the codon plays during translation Each codon specifies a particular amino acid or the end of translation
Which of the following is INCORRECT regarding the genetic differences among ethnic groups?
Genetic differences responsible for skin color represent a substantial portion of the human genome
27.4 Define genetic drift
Genetic drift: changes in allele frequencies in a population due to random fluctuations
Discuss how genetic information is passed from cell to cell and individual to individual.
Genetic material is transmitted from parent to offspring and from cell to cell For this transmission to occur, the genetic material must be copied DNA replication: the process in which original DNA strands are used as templates for the synthesis of new DNA strands
Distinguish between germ-line and somatic mutations
Germ-line mutations: can occur directly in a sperm or egg cell or it can occur in a precursor cell that produces the gametes If a mutant gamete participates in fertilization, all cells of the resulting offspring will contain the mutation Likewise, when an individual with a germ-line mutation produces gametes, the mutation may be passed along to future generations of offspring Somatic mutations: mutations can happen within somatic cells at early or late stages of development Has occurred within a single embryonic cell- as the embryo grows, this single cell is the precursor for many cells of the adult organism In the adult, a portion of the body contains the mutation The earlier the mutation occurs during development, the larger the affected region An individual that has somatic regions that differ genotypically from each other is called a genetic mosaic
Outline the three stages of transcription
Initiation: in transcription, the stage that involves the initial binding of RNA polymerase to the promoter in order to begin RNA synthesis Elongation: in transcription, the synthesis of an RNA transcript using DNA as a template Termination: in transcription, the release of the newly made RNA transcript and RNA polymerase from the DNA
13.6 Outline the 3 stages of translation and in general, what occurs during each stage
Initiation: the formation of a complex between mRNA, the initiator tRNA and the ribosomal subunits Elongation: the synthesis of a polypeptide using the information within mRNA Termination: the release of the polypeptide and the last tRNA and disassembly of the ribosomal subunits and mRNA
9.1 Analyze the experiments of 1) Griffith, 2) Avery, MacLeod and McCarty, and 3) Hershey and Chase and identify their importance.
Griffith's experiments indicated that genetic material can transform streptococcus He conducted experiments that involved the injection of live and/or heat-killed bacteria into mice The transformed bacteria acquired the information to make a capsule Among different strains, variation exists in the ability to create a capsule and to cause mortality in mice The genetic material that is necessary to create a capsule must be replicated so it can be transmitted from mother to daughter cells during cell division These observations are consistent with the idea that the formation of a capsule is governed by the bacteria's genetic material, meeting the four criteria described previously His experiments showed that some genetic material from the dead bacteria had been transferred to the living bacteria and provided them with a new trait Avery, MacLeod and McCarty showed that DNA is the substance that transforms bacteria They realized that Griffith's observations could be used as part of an experimental strategy to identify the genetic material They used established biochemical purification procedures and prepared extracts from type S bacteria strains that contained each type of these molecules After many repeated attempts with the different types of extracts, they discovered that only one of the extracts, namely, the one that contained purified DNA from type S bacteria was able to convert type R bacteria into type S To further verify that the DNA in the extract was responsible for the transformation, they treated samples of the DNA extract with enzymes that digest DNA- DNase, RNase, protease When DNA extracts were treated with RNase or protease, they still converted type R bacteria into type S- these results indicated that any RNA or protein in the extract was not acting as the genetic material When the extract was treated with DNase, it lost its ability to convert type R into type S bacteria The results indicated that the degradation of the DNA in the extract by DNase prevented conversion of type R to type S This interpretation is consistent with the hypothesis that DNA is the genetic material Hershey and Chase provided evidence that DNA is the genetic material of T2 phage: They asked: what is the biochemical composition of the genetic material that enters the bacterial cell during infection? They used radioisotopes to distinguish proteins from DNA Their results were consistent with the idea that the genetic material of bacteriophages is DNA, not proteins
An isolated population of tardigrades is able to protect itself from the effects of extreme doses of radiation. As a result they can survive in an environment that would kill other organisms. The mutation(s) that led to the ability to protect themselves:
Happened by chance
When the base composition of DNA from the bacterium Mycobacterium tuberculosis was determined, 18% if the bases were found to be adenine. What is the percentage of cytosine? What is the percentage of the remaining bases?
Have to use Chargaff's rule Numbers are not exactly the same but close enough Cytosine: 32% Thymine = 18% Guanine = 32%
Match the researcher(s) with the finding
Hershey and chase= DNA as the information storage molecule Meselson and Stahl= semiconservative model DNA replication Lederbergs= random mutation theory Beadle and Tatum= one gene - one enzyme hypothesis Watson and Crick= DNA as a double helix structure
Describe how mutations in the coding sequence of a gene may alter a polypeptide function
How mutations in the coding sequence of a gene may later polypeptide function Silent mutations: those that do not alter the amino acid sequence of the polypeptide even though the base sequence has changed Because the genetic code is degenerate, silent mutations can occur in certain bases within a codon, such as the third base and the specific amino acid is not changes Missense mutations: are base substitutions for which an amino acid change does result EX: the one that causes the human disease known as sickle cell disease Involves a mutation in the beta-globin gene, which alters the polypeptide sequence such that the sixth amino acid is changed from glutamic acid to valine This single amino acid substitution alters the structure and function of the hemoglobin protein One consequence of this alteration is that under conditions of low oxygen, the red blood cells assume a sickle shape A single amino acid substitution has a profound effect on the phenotype of cells and even causes a serious disease
3.1 Compare and contrast the similarities and differences between homologous chromosomes
How similar are homologous chromosomes? The sequence of bases of one homolog usually differs from the sequence of the other homolog by less than 1% EX: The DNA sequence of chromosome 1 that you inherited from your mother is more than 99% identical to the sequence of chromosome 1 that you inherited from your father It should be emphasized that the sequences are not completely identical The slight differences in DNA sequences provide the allelic differences in genes The striking similarities between homologous chromosomes do not apply to the pair of sex chromosomes- X and Y These chromosomes differ in size and genetic composition Certain genes that are found on the X chromosome are not found on the Y chromosome and vice versa The X and Y chromosomes are not considered homologous chromosomes even though they have short regions of homology
Evaluate the validity of a hypothesis using a chi-square test
Hypothesis testing: one experimental approach for conducting science It involves the formation of a hypothesis, which is followed by experimentation, so that scientists may reach verifiable conclusions about the world in which they live The goal is to determine if the data from genetic crosses are consistent with a particular pattern of inheritance To distinguish inheritance patterns that obey Mendel's laws from those that do not, a conventional strategy is to make crosses and then quantitatively analyze the offspring Hypothesis testing provides an objective, statistical method to evaluate whether the observed data really agree with the hypothesis We use statistical methods to determine whether the data that have been gathered from crosses are consistent with predictions based on quantitative laws of inheritance Goodness of fit: the degree to which the observed data and the data predicted from a hypothesis are similar to each other If the observed and predicted data are very similar, the goodness of fit is high Null hypothesis: a hypothesis that assumes there is no real difference between the observed and expected values Chi square test: a commonly used statistical method for determining the goodness of fit This method can be used to analyze population data in which the members of the population fall into different categories We typically have this kind of data when we evaluate the outcomes of genetic crosses, because these usually produce a population of offspring that differ with regard to phenotypes
ABO blood type is examined in a Taianese population and allele frequencies are determined. In the population, f(I^A) = 0.30, f(I^B) = 0.15, and f(i) = 0.55 Assuming hardy-weinberg conditions apply: What are the frequencies of genotypes? What are the blood group frequencies in this population?
IA= 0.30^2 IAi= 2 * 0.30 * 0.55 IBB= sq. root of 0.15 IBi= 0.15 * 0.55 * 2 ii= 0.55^2 IAB= 0.30 * 0.55 * 2 Blood type A is covered by the genotypic frequency of IAi and A= 0.42 B= 0.1875 AB= 0.09 O= 0.3025
9.6 Identify key structural features of the DNA double helix
In a DNA double helix, two DNA strands are twisted together around a common axis to form a structure that resembles a spiral staircase It is stabilized by base pairs (bp): the structure in which two nucleotides in opposite strands of DNA hydrogen bond with each other For example, an AT base pair is a structure in which an adenine-containing nucleotide in one DNA strand hydrogen bonds with thymine-containing nucleotide in the complementary strand If you count the bases along one strand, once you reach 10, you have gone 360 degrees around the axis of the helix The linear distance along a strand through such a complete turn is 3.4 nm- each base pair traverses 0.34 nm AT/GC rule: in DNA, the phenomenon in which an adenine base in one strand always hydrogen bonds with a thymine base in the opposite strand and a guanine always hydrogen bonds with a cytosine Three hydrogens bonds occur between G and C but only two between A and T DNA sequences with a high proportion of G and C tend to form more stable double-stranded structures
3.6 Explain the relationship between meiosis and Mendel's Laws of Inheritance
Law of segregation - segregation of homologous chromosomes during Meiosis I Law of independent assortment - Random alignment of bivalents during Meiosis I
An F1 plant with the genotype DdGg is mated to a ddgg plant. The resulting seeds are planted and the following phenotypes produced in these numbers (F2 offspring): DG 47 Dg 396 dG 412 dg 55 What are the specific allelic arrangements on chromosomes of the P generation that produced F1? What is the distance between the genes?
Linkage assortment because 2 classes are smaller and 2 are bigger You could have a dominant allele and/or a recessive allele The recombinants are 1 and 4 because their numbers are far less than the expected values The highest numbers (2 and 3) are considered parentals (non recombinant chromosomes) Dg / dG P generation: Dg/Dg and dG/dG Map units 11.2 mu
List the mechanisms that may cause allele and genotype frequencies to significantly change from one generation to the next
Mechanisms that alter existing genetic variation: Natural selection Genetic drift Migration Nonrandom mating
8.7 Describe how meiotic and mitotic nondisjunction occur and their possible phenotypic consequences
Meiotic nondisjunction: the event in which chromosomes do not segregate properly during meiosis If such a cell gives rise to a gamete that fuses with a normal gamete during fertilization, the resulting offspring will have an abnormal chromosome number in all of its cells Also may occur after fertilization in one of the somatic cells of the body Nondisjunction can occur during anaphase of meiosis I or meiosis II If it happens during meiosis I, an entire bivalent migrates to one pole Following the completion of meiosis, the four resulting haploid cells are abnormal If nondisjunction occurs during anaphase of meiosis II, the net result is two abnormal and two normal haploid cells If a gamete carrying an extra chromosome unites with a normal gamete, the offspring will be trisomic If a gamete that is missing a chromosome is viable and participates in fertilization, the resulting offspring is monosomic for the missing chromosomes Mitotic nondisjunction: an event in which chromosomes do not segregate properly during mitosis Abnormalities in chromosome number occasionally occur after fertilization takes place The abnormal event happens during mitosis rather than meiosis One possibility is that the sister chromatids separate improperly, so one daughter cell receives three copies of a chromosome, whereas the other daughter cell gets only one Alternatively, the sister chromatids can separate during anaphase of mitosis, but one of the chromosomes is improperly attached to the mitotic spindle apparatus and so does not migrate to a pole A chromosome will be degraded if it is left outside the nucleus when the nuclear membrane reforms One of the daughter cells has two copies of that chromosome, whereas the other has only one
2.2 Analyze Mendel's experiments involving monohybrid (single-factor) crosses
Mendel carried out self-fertilization or cross-fertilization experiments with his pea plants Single-factor cross: a cross in which an experimenter is following the outcome of only a single character Monohybrid: an individual produced from a single-factor cross in which the parents had different variants for a single character His experiments were designed to determine the relationships that govern hereditary traits- empirical approach: a strategy in which experiments are designed to determine quantitative relationships as a way to derive laws that govern biological, chemical or physical phenomena He began with true-breeding plants that differed in a single character parental generation (P gen): in a genetic cross, the first generation in the experiment- in Mendel's studies, the parental generation was true-breeding with regard to particular traits Crossing true-breeding parents to each other, called a P cross, produces the offspring that constitute the F1 generation F1 generation: the offspring produced from a cross of a parental generation This prompted Mendel to follow the transmission of this character for one additional generation The plants of the F1 generation were allowed to self-fertilize to produce a second generation called the F2 generation F2 generation: the offspring produced from a cross or self-fertilization of the F1 generation
Define the Law of Independent Assortment and explain how it can promote genetic variation
Mendel's law of independent assortment: two different genes will randomly assort their alleles during gamete formation (if they are not linked) Independent assortment allows for new combinations of alleles of different genes to be found in future generations of offspring
Define the Law of Segregation and explain how it is related to gamete formation and fertilization
Mendel's law of segregation: the two copies of a gene segregate (or separate) from each other during transmission from parent to offspring
27.2 Define microevolution
Microevolution: changes in a population's gene pool with regard to particular alleles over measurable periods of time
27.5 Explain how migration affects allele frequencies between neighboring populations
Migration between two different established populations can alter allele frequencies Gene flow: transfer of alleles or genes from one population (a donor population) to another, thereby changing the recipient population's gene pool One way this occurs is by the migration of fertile individuals from one population to another population and the successful breeding of such migrants with the members of the recipient population Gene flow depends not only on migration, but also on the ability of the migrants' alleles to be passed to subsequent generations To determine the effects of migration, we need to consider three populations: The original donor population The original recipient population The population that has new members due to migration We must know what proportion of the conglomerate population (a population composed of members of an original population plus new members that have migrated from another population) the migrants represent
Compare and contrast the key differences between mitosis and meiosis both in terms function, phases and chromosome states (see also Table 3.1)
Mitosis produces two diploid daughter cells with six chromosomes each, whereas meiosis produces four haploid daughter cells with three chromosomes each Meiosis halves the number of chromosomes per cell
19.4 Define mutagen
Mutagen: an agent that can alter the structure of DNA, causing a mutation Mutagen agents are usually classified as chemical or physical mutagens
List the mechanisms that may cause allele and genotype frequencies to significantly change from one generation to the next (2)
Mutation Migration Non-random mating Selection Random Genetic Drift Therefore, assumptions of a population at Hardy Weinberg Equilibrium are as follows: No mutation No migration Random Mating No Selection Large population bc random sampling of gametes in large populations has less of an effect. No Random Genetic Drift.
Explain the role of mutation in microevolution
Mutation: random mutations within preexisting genes introduce new alleles into populations, but at a very low rate New mutations may be beneficial, neutral or deleterious For new alleles to rise to a significant percentage in a population, other evolutionary mechanisms (natural selection, genetic drift, and/or migration) must operate on them
27.3 Explain the process of natural selection
Natural selection: refers to the process whereby differential fitness acts on the gene pool When a mutation creates a new allele that is beneficial, the allele may become prevalent within future generations because the individuals possessing the allele are more likely to reproduce than pass it to their offspring
13.1 Understand the genetic basis for protein synthesis, i.e. the One gene, one enzyme hypothesis
One-gene/ one-enzyme hypothesis: the idea, which later needed to be expanded, that one gene encodes one enzyme The hypothesis then had to be modified in 4 ways: Enzymes are only one category of proteins- all proteins are encoded by genes, and many of them do not function as enzymes Some proteins are composed of two or more different polypeptides- therefore, it is more accurate to say that a protein-encoding gene encodes a polypeptide Many genes do not encode polypeptides- several types of gene specify functional RNA molecules that do not encode polypeptides One gene can encode multiple polypeptides due to alternative splicing and RNA editing
You have isolated and determined the mRNA sequence for a targeted Eukaryotic gene. Why won't you have data on all parts of the gene?
Only the exons are translated
Analyze a pedigree to determine if a trait or disease is dominant or recessive
Pedigree analysis is commonly used to determine the inheritance pattern for human genetic diseases Human geneticists are routinely interested in knowing whether a genetic disease is inherited as recessive or dominant trait One way to discern the dominant/recessive relationship between two alleles is by pedigree analysis Genes that play a role in disease may exist as a common (wild-type) allele or a mutant allele that causes disease symptoms If the disease follows a simple Mendelian pattern of inheritance and is caused by a recessive allele, an individual must inherit two copies of the mutant allele to exhibit the disease A recessive pattern of inheritance makes two important predictions First, two heterozygous unaffected individuals will, on average, have ¼ of their offspring affected Alternatively with a dominant trait, affected individuals will have inherited the gene from at least one affected parent (unless a new mutation has occurred during gamete formation)
8.4 Define pericentric and paracentric inversions
Pericentric inversion: if the centromere lies within the inverted region of the chromosome Paracentric inversion: if the centromere is found outside the inverted region
4.3 Discuss the role of the environment with regard to an individual's traits
Phenylketonuria exhibits and recessive inheritance pattern and the mutant allele is a loss-of-function allele The consequences of PKU are inability to metabolize phenylalanine (an amino acid) and thus individual's mental development is impaired as Phenylalaine builds up in their system However, when individuals homozygous for PKU alleles are fed a low protein diet, development may proceed properly and symptoms are mitigated.
19.1 Define point mutation
Point mutation: a change in a single base pair within DNA EX: a DNA sequence has been altered by a base substitution (a point mutation in which one base is substituted for another), in which one base is substituted for another
Describe the extent of polymorphism in natural populations (2)
Polymorphic vs monomorphic, Single Nucleotide polymorphisms - smallest type of genetic change that can occur. Bulk of the genetic variation in humans, defined as a single change in the DNA sequence at a particular location. Must be present in at least 1% of a random sample of individuals to be defined as a SNP.
Describe the extent of polymorphism in natural populations
Polymorphism: "many forms" refers to the observation that many traits display variation within a population First referred to variation in traits that are observable with the naked eye In color and pattern have long attracted the attention of population geneticists
Compare and contrast polyploidy and aneuploidy
Polyploid: describes an organism or cell with three or more sets of chromosomes Difference between aneuploidy and polyploidy: Fig. 8.15
Describe and interpret mechanisms generating variation in natural populations and its importance in population genetics and evolution.
Prevalent alleles in a natural population as: wild-type alleles: an allele that is fairly prevalent in a natural population, generally found in more than 1% of the population For polymorphic genes, there is more than one wild-type allele Mutant alleles tend to be rare in natural populations Though dominant mutant alleles are much less common than recessive mutant alleles, they do occur in natural populations Gain-of-function mutations: a mutation that changes a gene product so that it gains a new or abnormal function Dominant-negative mutation: a mutation that produces an altered gene product that acts antagonistically to the normal gene product Shows a dominant pattern of inheritance Haploinsufficiency: the phenomenon in which an individual has only a single functional copy of a gene and that single functional copy does not produce a normal phenotype Shows a dominant pattern of inheritance
2.5 Define probability
Probability: the chance that an outcome will occur in the future probability= number of times a particular outcome occurs / total number of possible outcomes
Predict the outcome of crosses using the product rule
Product rule: the probability that two or more independent outcomes will occur is equal to the products of their individual probabilities The cross: Pp x Pp Step one: calculate the individual probability of this phenotype- this is accomplished using a punnett square Step two: multiply the individual probabilities
3.4 Review meiosis - cell to gametes to individual
Prophase of meiosis I: Lepotone: the first stage of prophase of meiosis I The replicated chromosomes begin to condense and become visible with a light microscope Zygotene: the second stage of prophase of meiosis I Involves a recognition process known as: Synapsis: the event in which homologous chromosomes recognize each other and then align themselves along their entire lengths Pachytene: the third stage of prophase of meiosis I The homologs have become completely aligned Bivalents: a structure in which two pairs of homologous sister chromatids have synapse (aligned) with each other Tetrad: the structure formed by the association of four sister chromatids during meiosis Crossing over: a physical exchange of pieces between homologous chromosomes that most commonly occurs during prophase of meiosis I Chiasma: the site where crossing over occurs between two chromosomes It resembles the Grek letter chi, X Diplotene: the fourth stage of prophase of meiosis I The synaptonemal complex has largely disappeared The chromatids within a bivalent pull apart slightly and it becomes easier to see under a microscope that a bivalent is actually composed of four sister chromatids Diakinesis: the fifth stage of prophase of meiosis I The synaptonemal complex completely disappears Prometaphase of meiosis I: The spindle apparatus is complete and the chromatids are attached via kinetochore microtubules Metaphase of meiosis I: The bivalent (tetrads) are organized along the metaphase plate The pair of sister chromatids are aligned in a double row rather than a single row, as occurs in mitosis The arrangement of sister chromatids (dyads) within this double row is random with regard to the blue and red homologs In addition to the random arrangement of homologs within a double row, a second distinctive feature of metaphase of meiosis I is the attachment of kinetochore microtubules to the sister chromatids One pair of sister chromatids is linked to one of the poles and the homologous pair is linked to the opposite pole This arrangement is quite difference from the kinetochore attachment sites during mitosis, in which a pair of sister chromatids is linked to both poles Anaphase of meiosis I: The two pairs of sister chromatids within a bivalent separate from each other The connection that holds sister chromatids together does not break Instead, each joined pair of chromatids migrates to one pole and the homologous pair of chromatids moves to the opposite pole Telophase of meiosis I: The sister chromatids have reached their respective poles and decondensation occurs in most but not all species Meiosis II: For a diploid organism with six chromosomes, mitosis begins with 12 chromatids that are joined as six pairs of sister chromatids
3.3 Review mitosis - cell to cell
Prophase: the first phase of mitosis the chromosomes have already replicated and begin to condense The mitotic spindle apparatus starts to form Prometaphase: the second phase of mitosis During this phase, the nuclear membrane vesticulates and the mitotic spindle is completely formed Metaphase: the third phase of mitosis The chromosomes align along the central plane of the spindle apparatus and the formation of the spindle is completed Anaphase: the fourth phase of mitosis As anaphase proceeds, half of the chromosomes move to one pole and the other half move to the other pole Telophase: the fifth stage of mitosis The chromosomes have reached their respective poles and decondense Cytokinesis: the division of a single cell into two cells The two nuclei produced in mitosis are segregated into separate daughter cells during cytokinesis Outcome of mitotic cell division: mitosis and cytokinesis ultimately produce two daughter cells having the same number of chromosomes as the mother cell The two daughter cells are genetically identical to each other and to the mother cell from which they were derived
13.4 Outline structural features of ribosomes, i.e. E, P, & A sites, small and large subunits
Ribosome: a large macromolecular structure that acts as the catalytic site for polypeptide synthesis The ribosome allows the mRNA and tRNAs to be positioned correctly as the polypeptide is made The ribosome can be thought of as the macromolecular arena where translation takes place A site: Binding of charged tRNA to the A site- to begin elongation, a charged tRNA brings a new amino acid to the ribosome so that it can be attached to the end of the growing polypeptide At the top of which describes bacterial translation, a short polypeptide is attached to the tRNA located at the P site of the ribosome A charged tRNA carrying a single amino acid binds to the A site This binding occurs because the anticodon in the tRNA is complementary to the codon in the mRNA The hydrolysis of GTP by the elongation factor EF-Tu provides energy for the binding of a tRNA to the A site Peptidyl transfer: the step during the elongation stage of translation in which the polypeptide is removed from the tRNA in the P site and transferred to the amino acid at the A site This transfer is accompanied by the formation of a peptide bond between the amino acid at the A site and the polypeptide, lengthening the polypeptide by one amino acid Peptidyl transferase: a complex that functions during translation to catalyze the formation of a peptide bond between the amino acid in the A site of the ribosome and the growing polypeptide Translocation: after the peptidyl transfer reaction is complete, the ribosome moves or translocates to the next codon in the mRNA This moves the tRNAs at the P and A sites to the E and P sites The uncharged tRNA exits the E site The next codon in the mRNA is now exposed in the unoccupied A site At this point, a charged tRNA can enter the empty A site and the same series of steps adds the next amino acid to the growing polypeptide The A, P and E sites are named for the role of the tRNA that is usually found there The A site binds aminoacyl-tRNA (charged tRNA) The P site usually contains the peptidyl-tRNA (a tRNA with an attached peptide) The E site is where the uncharged tRNA exits
Which of the following would contain genetic material that is 100% identical
Sister chromatids
19.3 Distinguish between spontaneous and induced mutations
Spontaneous mutations: a change in DNA structure that results from natural biological or chemical processes EX: Abberrant recombination Aberrant segregation Errors in DNA replication Toxic metabolic products Transposable elements Depurination Deamination Tautomeric shifts Induced mutations: a change in DNA structure caused by an environmental agent EX: Chemical agents Physical agents
9.7 Outline the key structural features of RNA
Strands of RNA are usually a few hundred to several thousand nucleotides in length- much shorter than chromosomal DNA, which is typically millions of base pairs long When RNA is made during transcription, the DNA is used as a template In most cases, only one of the two DNA strands is used as a template for RNA synthesis- therefore, only one complementary strand of RNA is usually made Base pairing between A and U and between G and C may occur within one RNA molecule or between two separate RNA molecules This base pairing causes short segments of RNA to form a double-stranded region that is helical Different arrangements of base pairing are possible, which result in structures called a bulge loop, an internal loop, a multibranched junction and a stem-loop (hairpin) These structures contain regions of complementarity punctuated by regions of non complementarity The complementary regions are held together by hydrogen bonds between base pairs, whereas the non complementary regions have their bases projecting away from the double-stranded region Many factors contribute to the structure of RNA molecules: Hydrogen bonding between bases in base pairs Stacking between bases Hydrogen bonding between bases Backbone regions Interactions with ions Small molecules Large proteins In a living cell, various regions of an RNA molecule fold and interact with each other to produce the three-dimensional structure
9.4 Describe the structural features of a DNA strand
Sugar phosphate backbone, phosphodiester linkages between the adjacent nucleotides, bases project from the backbone, which is negatively charged, orientation of nucleotides, all sugar molecules have the same orientation. Specific order to the sequence.
6.1 Define genetic linkage and explain how linkage affects the outcome of crosses
Synteny is physical linkage whereas genetic linkage is when different genes are inherited as a unit or do not follow independent assortment Genetic linkage occurs when genes are separated by less than 50 map units
3.2 List and outline the phases of the eukaryotic cell cycle
Synthesis - DNA replication occurs, first appearance of the chromatids. G2 - Maintenance and generation of proteins and RNA molecules necessary for cell division M phase - mitosis or meiosis, depending on cell type. Nuclear division Cytokinesis - cytoplasmic division G1 - Maintenance and preparation for DNA replication
14.2 Describe the organization of the lac operon and the associated regulatory gene
The CAP site is the binding site for the catabolite activator protein (CAP) The operator site is a binding site for lac repressor The promoter (lacP) is responsible for the transcription of the lacZ, lacY and lacA genes as a single unit, which ends at the lac terminator The i promoter is responsible for the transcription of the lacI gene Lactose permease allows the uptake of lactose into the bacterial cytoplasm It co-transports lactose with H+ Because bacteria maintain an H+ gradient across their cytoplasmic membrane, this co-transport permits the active accumulation of lactose against a gradient Beta-galactosidase is a cytoplasmic enzyme that cleaves lacrosse and related compounds into galactose and glucose As a minor side reaction, beta-galactosidase also converts lactose into allolactose Allolactose can also be broken down into galactose and glucose
14.1 Describe the function of activators and repressors and define positive and negative control
The Regulatory Proteins Involved 1) Repressors • Bind to DNA and inhibit transcription • Negative control refers to transcriptional regulation by repressor proteins 2) Activators • Bind to DNA and increase transcription • Positive control refers to transcriptional regulation by activator proteins
Assuming independent assortment, what is the probability that an offspring will have an SsRR genotype from a cross of two SsRr individuals?
The S gene and the R gene are assumed to be on different chromosomes or 50 mu apart Can use fork line method or two monohybrid crosses and get frequency of heterozygote and homozygote Once you get the probabilities you multiply them- you want the two individuals to produce a homozygous for first and heterozygous for second Ss = ½ and RR = ¼ = ⅛
12.4 List the different types of RNA modifications (Table 12.2) - focus on Eukaryotes
The cleavage of a large RNA transcript into smaller pieces One or more of the smaller pieces becomes a functional RNA molecule Splicing involves both cleavage and joining of RNA molecules The RNA is cleaved at two sites, which allows an internal segment of RNA known as an intron, to be removed After the intron is removed, the two ends of the RNA molecules are joined together The attachment of a 7-methylguanosine cap to the 5' end of the mRNA The cap plays a role in the splicing of introns, the exit of mRNA from the nucleus and the binding of mRNA to the ribosome The attachment of a string of adenine containing nucleotides to the 3' end of the mRNA at a site where the mRNA is cleaved It is important for RNA stability and translation in eukaryotes The base sequence of an RNA is changed after it has been transcribed The covalent modification of a base within an RNA molecule
Explain how inbreeding affects the Hardy-Weinberg equilibrium
The effects of inbreeding and outbreeding can also be examined at the population level
In a chi square test to determine if two genes are linked or assorting independently, what is the default (null) hypothesis stated
The genes are assorting independently (not linked because it would be harder to determine probability of each offspring)
Explain how the lac operon is regulated by lac repressor and by catabolite activator protein
The lac operon can be transcriptionally regulated in more than one way The first mechanism is inducible and under negative control This form of regulation involves lac repressor, which is a protein that binds to the sequence of nucleotides found within the lac operon site Once boud, the lac repressor prevents RNA polymerase from transcribing the lacZ, lacY and lacA genes The binding of the repressor to the operator site is a reversible process In the absence of allolactose, lac repressor is bound to the operator site most of the time The ability of the lac repressor to bind to the operator site depends on whether or not allolactose is bound to it Each of the repressor protein's four subunits has a single binding site for allolactose, the inducer When four molecules of allolactose bind to the repressor, a conformational change occurs that prevents lac repressor from binding to the operator site Under these conditions, RNA polymerase is free to transcribe the operon- or it has been induced
A woman and a man, each have a wildtype phenotype, have a son with Klinefelter syndrome (XXY) who has hemophilia, an X-linked recessive disorder. In which parent, mother or father, did nondisjunction occur? Did nondisjunction occur during Meiosis I or Meiosis II?
The mother because she is the only one who has the recessive allele (dad does not) Most likely Meiosis II
9.3 Describe the structure of a nucleotide and importance of carbon designations 5' and 3'
The nucleotide is the repeating structural unit of both DNA and RNA Has three components: At least one phosphate group A pentose sugar Nitrogenous base Nucleotides vary with regard to the sugar and the nitrogenous base In a single nucleotide, the base is always attached to the 1' carbon atom and one or more phosphate groups are attached at the 5' position The -OH group attached to the 3' carbon is important in allowing nucleotides to form covalent linkages with each other
2.4 Describe the features of a pedigree
The oldest generation is at the top of the pedigree, and the most recent generation is at the bottom Vertical lines connect each succeeding generation A man (square) and woman (circle) who produce one or more offspring are directly connected by a horizontal line A vertical line connects parents with their offspring If parents produce two or more offspring, the group of siblings (brothers and/or sisters) is denoted by two or more squares and/or circles projecting downward from the same horizontal line
8.3 Explain how deletions and duplications occur and how these events affect the phenotype of an organism
The phenotypic consequences of a chromosomal deletion depend on the size of the deletion and whether it includes genes or portions of genes that are vital to the development of the organism When deletions have a phenotypic effect, it is usually detrimental- larger deletions tend to be more harmful because more genes are missing Many examples are known in which deletions affect phenotype EX: a human genetic disease known as cri-du-chat syndrome is caused by a deletion of a segment in the short arm of human chromosome 5- display an array of abnormalities including mental deficiencies, unique facial anomalies, and in infancy, an unusual catlike cry As with deletions, the phenotypic consequences of duplications tend to be correlated with size Duplications are more likely to have phenotypic effects if they involve a large piece of a chromosome In general, small duplications are less likely to have harmful effects that are deletions of comparable size This observation suggests that having only one copy of a gene is more harmful than having three copies In humans, relatively few well-defined syndromes are caused by small chromosomal duplications EX: Charcot-Marie-Tooth disease (type 1A), a peripheral neuropathy characterized by numbness in the hands and feet that is caused by small duplication on the short arm of chromosome 17
Random genetic drift can act in populations to either favor the loss or fixation of an allele. Which of the following statements is correct
The rate of loss and/or fixation of an allele is slower in larger versus small populations
Trisomy 8 usually leads to early miscarriage of a fetus. However, adult individuals have found that with cells that have three copies of chromosome 8 in then. How can this be?
The trisomic 8 adults likely have a mosaic region with trisomy 8
A transversion mutation occurs within the transcribed region of mRNA. What is the impact on the protein translated from this mRNA?
There is not enough information to determine the impact
Mutations in DNA occur in the genomes of most organisms, including humans. What is the most important result of these mutations?
They provide genetic variation
Which of the following is a characteristic of mutations in DNA?
They result in different versions of a gene within a population if they occur in coding regions and Mutation rates are very low
Explain why loss-of-function alleles often follow a recessive pattern of inheritance
Think about in terms of protein production Two possible explanations: 1) In a heterozygote, 50% of the wild-type allele is able to produce the same phenotype as the homozygotes for the wild-type allele 2) When recessive, loss of function allele is present (heterozygote), the wild-type allele is upregulated or over expressed to compensate for the loss of the 50% due to the mutant allele.
19.2 Analyze the results obtained by the Lederbergs and explain how they are consistent with the random mutation theory
To distinguish between the physiological adaptation and random mutation hypotheses, Joshua and Esther Lederberg developed a technique known as replica plating (a technique in which replicas of bacterial colonies are transferred to new growth) in the 1950s They plated a large number of bacteria onto a master plate that did not contain any selective agent (namely, no T1 phage) A sterile piece of velvet cloth was later lightly touched to this plate in order to pick up a few bacterial cells from each colony These replicas were then transferred to two secondary plates that contained an agent that selected for the growth of bacterial cells with a particular mutation On the secondary plates, only those mutant cells that are resistant to lysis by T1 phage (ton r mutations) could grow The results indicated that the ton r mutations occurred randomly while the cells were growing on the nonselective master plate The presence of the T1 phage in the secondary plates simply selected for the growth of previously occurring ton r mutants These results supported the random mutation hypothesis- in contrast, the physiological adaptation hypothesis would have predicted that ton r mutants would occur after the exposure to the selective agent on the secondary plates If that had been the case, the colonies would be expected to arise not in identical locations on different secondary plates but rather in different patterns The results of the Lederbergs supported the random mutations hypothesis known as the random mutation theory: according to this theory, mutations are random events- they can occur in any gene and do not require exposure of an organism to an environmental condition that causes specific types of mutations
What is the function(s) of a telomere?
To prevent loss of vital genetic information and Prevents chromosomes from sticking together- blocks end joining
Given that mutations are random, what would be the most likely set of anticipated results from a Lederberg experiment with replica plating?
Total number of colonies on a plate: 1500 and Total number of resistant colonies on replica plate with T1: 150
Define the two types of translocations and understand how each can affect the phenotype of an organism
Two types of translocations: Balanced translocation: a translocation, such as a reciprocal translocation, in which the total amount of genetic material remains normal or nearly normal Usually occur without any phenotypic consequences because the individual has a normal account of genetic material Can result in position effects similar to those that can occur inversions Unbalanced translocation: a translocation in which a cell has too much or too little genetic material compared with a normal cell Significant portions of genetic material are duplicated and/or deleted Generally associated with phenotypic abnormalities or may even be lethal
2.3 Analyze Mendel's experiments involving dihybrid (two-factor) crosses
Two-factor cross: a cross in which an experimenter follows the outcome of two different characters These experiments led to the formulation of a second law- the law of independent assortment What results are possible from a two-factor cross? One possibility is that the genetic determinants for these two different characters are always linked to each other and inherited as a single unit An F1 offspring could only produce two types of gametes A second possibility is they are not linked and can assort themselves independently into gametes An F1 offspring could produce four types of gametes F2 generation were nonparental: refers to a combination of traits not found in the true-breeding parental generation The occurrence of nonparental variants contradicts the linked-assortment hypothesis
4.2 Define wild-type allele and genetic polymorphism
Wild-type alleles: prevalent alleles in a population Genetic polymorphism: when more than one wild type allele is observed in a population.
Due to a crossing over with an inversion loop:
a heterozygote with a pericentric inversion may produce gametes
Cystic fibrosis is caused by mutation in the CFTR gene. There are several different mutant alleles that are known to result in cystic fibrosis disease. The CFTR mutant alleles behave as recessive alleles to the wildtype CFTR allele. If two carriers (heterozygous) that have different mutations in their CF genes have a child: a. What is the probability that the child will have CF disease? b. What is the probability that the first two children will have CF and the 3rd child will not?
a. 1/4 b. Ordered because it says the first two children will have CF and the 3rd will not ¼ * ¼ * ¾ = 3/64
In a heterozygote with a paracentric inversion and crossing over within an inversion loop, you are more likely to observe gametes that are missing chromosomes
because the recombinant chromosomes have either no centromere or two centromeres
The significance of mutations in microevolution is to:
create new alleles
3.5 Define sexual reproduction
individual to individual (i.e. via fertilization involving gametes)
negative control
repressor and inducer
