Biology 1
Chorionic villus sampling
"CVS" ----->
Hundreds of thousands of years of breeding
(artificial selection)
Ancestral dog
(wolf)
Intro to Evolution & Natural Selection
*next slides*
The Theory of Evolution by Natural Selection
*next slides*
Meiosis reduces the chromosome number by
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Chromosome duplication & distribution during cell division
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Multiple alleles for the ABO blood groups
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Aminocentesis
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Two diploid daughter cells, genetically identical to parent cell
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polygenic inheritance phenotypes:
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Antigen & Antibody Characteristics & the ABO group.
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Schematic model with mRNA & tRNA
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codon table for mRNA
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Protein Synthesis
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Mendel & The Gene Idea
---next slides---
Functioning Ribosome
--computer model->
Populations & Gene Pools...contd.
-A pop. can be characterized by the frequency of alleles for a given trait. --The abundance of a particular allele in relation to the sum of alleles at that locus. -The sum of all the alleles for all traits in a sexually reproducing population is called the gene pool.
What is Evolution?
-According to Charles Darwin, evolution is "descent with modification". Simply means that populations change over time. -Populations consist of individuals of the same species that occupy a given area at the same time. -They share a unique set of genes.
Cracking the Code
-All 64 codons were deciphered by the mid-1960s Of the 64 triplets, 61 code for amino acids; 3 triplets are "stop" signals to end translation. -The genetic code is redundant (more than one codon may specify a particular amino acid) but not ambiguous; no codon specifies more than one amino acid. -Codons must be read in the correct reading frame (correct groupings) in order for the specified polypeptide to be produced.
Sexual Reproduction (Meiosis)
-Another form of cell division, meiosis, occurs within gonads, or sex organs. -Male gonads are testes & female gonads are ovaries. -Meiosis produces sex cells: Gametes: --Male gametes: sperm cells. --Female gametes: egg cells.
Oogenesis (in humans)
-At birth, human female has in her ovaries approximately 1-2 million primary oocytes, but their development was suspended in early prophase of meiosis I. -By time she reaches puberty (age 10-13 years), only about 400,000 of the original primary oocytes remain alive. Others have degenerated, are never replaced.
Wolves are sometimes observed to have black coats and blue eyes. Assume that normal gray coat color (G) is dominant to black (g) and brown eyes (B) are dominant to blue (b). Suppose an alpha male who is black with blue eyes mates with the alpha female who is heterozygous for gray color and brown eyes. Out of 16 offspring, how many would be expected to have black coat color with blue eyes? Black coat color with brown eyes?
-Black coat, blue eye = 4/16 or 1⁄4 or 25% -Black coat, brown eye = 4/16 or 1⁄4 or 25%
Mitosis & Meiosis
-Both are types o f cell division. -Occur in diff. types of cells. -Produce very diff. products.
Meiosis: Each homologous pair has the same genes-
-Both chromosomes will have the genes on them in the exact same place. -Slightly different versions of each gene are called alleles. ----for color of garden pea, the alleles may be either yellow or green. ----for ear lobes in human, may be either attached for free.
Second Special Case of Genetic Drift
-Bottleneck Effect --The # of individuals in a population is drastically reduced.
Fruit Flies
-Can be easily grown in a container filled with food. -To safely work with them, they have to be anesthetized & delicately manipulated with a small brush. -Can be anesthetized with SmartNap Fly anesthetic. -Can develop to an adult in approximately 10 days.
Evolutionary Mechanisms
-Chance often plays an important role in the perpetuation of genes in a population, and the smaller the population, the more significant chance may be. -Chance events influencing the frequencies of genes in populations results in genetic drift --Analogous to flipping a coin.
Galapagos Islands
-Darwin also noticed that the Galapagos finches bore similarities suggestive of common ancestry. --Descendants of finches on the mainland of South America. -Finches ended up on the islands by chance & encountered new habitats with few competitors & predators.
Meiosis...cont'd.
-During meiosis, the homologous pairs are separated, so each cell has only one of each pair. -This condition is called haploid (n)-having only one of each kind of chromosome.
Meiosis...cont'd.
-During the S phase of Interphase, the DNA is copied & homologous chromosomes consist of sister chromatids. -All four sister chromatids carry the same genes at the same locations, but not necessarily the exact same information. (call be diff. alleles for any one gene)
Cycle Variability
-Estrous cycle variability differs among species, but cycles typically more frequent in smaller animals. -Even within species significant variability can be observed, thus cats may undergo an estrous cycle of 3 to 7 weeks. -Domestication can affect estrous cycles due to changes in the environment. -Estrous Frequency --Some species, such as cats, cows, & domestic pigs, are polyestrous, meaning they can go into heat several times per year, and or several times per season.
Common Misconceptions
-Evolution is a theory about the origin of life!* -Evolution theory implies that life evolved (and continues to evolve) randomly, or by chance.* -Evolution results in progress; organisms are always getting better through evolution.* -Individual organisms can evolve during a single lifespan.* -Climates changes, rivers shift course, new competitors invade & and organism with traits that are beneficial in one situation may be poorly equipped for survival when the environment changes.*
Menstrual Cycling
-Female Mammals who are Primates, including Humans. -Monthly cycles of ovulation (though not all cycles include successful ovulation) & buildup of endometrium (uterine lining in preparation for potential pregnancy) --followed either by pregnancy or by menstruation, which is also called "a period" =shedding of uterine lining or endometrium, which flows out of the vagina. -Beings at puberty, and ends at menopause (either oocytes are depleted, or ovaries surgically removed) -Regulated by hormones from pituitary & ovary.
First Special Case of Genetic Drift
-Founder Effect --A few individuals from a parental population colonize a new habitat. -Seldom carry alleles in the same frequency as the alleles in the gene pool from which they came. --The new colony that emerges shows far less genetic variation than the larger population.
Meiosis
-Gametes have half the chromosomes do (23 human) that somatic cells do (46 human). -Meiosis reduces the number of chromosomes by one-half. -Fertilization of the male & female gamete will result in 46 chromosomes.
Multiple Alleles
-Genes for a particular trait are at the same position on a chromosome. -The gene's position the chromosome is called its locus. -Numerous human loci have multiple alleles: --EXAMPLE: Blood type.
Heritable Variation & Patterns of Inheritance
-Heredity is the transmission of traits from one generation to the next. -Genetics is the scientific study or heredity. -Gregor Mendel --Worked in the 1860s. --Was the first person to analyze patterns of inheritance, and deduced the fundamental principles of genetics.
Darwins Theory: EXPLAINED
-How the finches of the Galapagos Islands changed over time -How some animals could become extinct: climate changes, food shortages, and other environment stressors could lead to extinction.
Human Chromosomes
-Humans have 23 pairs of chromosomes (46 total). -22 pairs of autosomes. -1 pair of sex chromosomes.
Human Fertilization (or conception)
-Humans when the sperm cell reaches the egg cell (ovum) and inserts its DNA into the egg -During sexual intercourse about 150 to 300 million sperm cells are released and travel through the vagina into the uterus. -Some sperm will successfully travel up the oviducts, but only a few hundred of these actually make it to the waiting egg (which could randomly be in either oviduct on any given month) --sperm cell may live 6-7 days inside female reproductive tract. -Only a single sperm cell can actually enter the egg cell to fertilize it. HUMAN FERTILIZATION NORMALLY OCCURS WITHIN THE OVIDUCT!
Incomplete Dominance
-Incomplete dominance is an interaction between two alleles that are expressed more or less equally. --The heterozygote is different from the homozygotes.
Populations & Gene Pools
-Individuals DO NOT evolve -Evolution requires that genetic changes are passed from one generation to another within populations. --Ind. within a pop. generally have the same # of genes & the same kinds of genes. --Varying expressions of genes at each locus are called? --Allele??--
Asexual Reproduction (also Mitosis)
-Make exact copies. -Does not need 2 parents. -Found in single celled organisms like in Amoeba.
Meiosis..contd.
-Meiosis is preceded by interphase (G1, S, G2) and followed by cell division. -Meiosis consists of phases : --Meiosis I, in which the homologous pairs are separated. --Meiosis II, in which the sister chromatids are separated.
Meiosis...cont'd.
-Meiosis occurs in the sex organs (either the testes or ovaries) producing haploid sperm or egg cells. -When the egg is fertilized , a zygote is formed. -A zygote is a diploid (2n) - the have two of each kind of chromosome.
Gregor Mendel's Discoveries
-Mendel brought an experimental & quantitative approach to genetics. -Mendel discovered the "behavior" of genes. -Mendelian inheritance reflects rules of probability.
Estrous Cycling
-Most other female mammals have Estrous Cycles. -Animals that have estrous cycles reabsorb most of the endometrium if there is no pregnancy in that cycle. -Animals that have menstrual cycles shed the endometrium through menstruation instead. -In species with estrous cycles, --Females are generally only sexually active during one phase (the estrus phase) of their cycle, which is also referred to as being "in heat" -Length of cycles & frequency of cycles varies widely between species.
Codominance
-Occurs when the heterozygote expresses the phenotype of both homozygotes. Example: In the ABO blood types, IAIB expresses both alleles and this individual has AB blood tyle.
Which 23 chromosomes end up in a gamete?
-One of each kind. -Chromosomes come in pairs (homologous pairs) -Each somatic cell has 2 of every chromosome (one from father, one from mother, carry same genes but may come in slighty different versions=alleles) -Each gamete has only one chromosome from each homologous pair.
Barriers that prevent mating: Prezygotic Barriers
-Physical isolation (rivers, mountains, etc) -Behavioral isolation -Temporal isolation (seasonal reproductive patterns) -Mechanical isolation
Basic Principles of Transcription & Translation
-RNA is the bridge between genes and the proteins for which they code. -Transcription is the synthesis of RNA using info in DNA. -Transcription produces messenger RNA (mRNA). -Translation is the synthesis of a polypeptide, (protein) using info in the mRNA. -Ribosomes are the sites of translation.
Other Evolutionary Mechanisms: Inbreeding
-Reduces genetic variation
Cell Division Overview
-Simple Cell Division (Mitosis) produces new cells in order to: -Heal wounds, -Replace damaged cells. -For growth & development. -Also for asexual reproduction in some types of organisms.
Populations & Gene Pools...contd
-Sources of variation within a population: 1. Independent assortment of chromosomes that results in the random distribution of chromosomes into gametes. 2. Crossing-over that results in a shuffling of alleles between homologous chromosomes. 3. Chance fertilization of an egg by a sperm cell. 4. Mutations of existing alleles (*only source of new alleles)
Steps for the lab of Covid testing:
-Start by extracting any RNA present in the nasal swab. Use kits to get the RNA out. -Next, an enzyme called reverse transcriptase is added to the reaction mixture to convert all the RNA to DNA. This creates a DNA blueprint that matched original RNA seq. from the swab & can be used to perform PCR. -PCR is then started. If the nasal swab does not have any virus, then no viral RNA can be extracted and no viral DNA can be made. If present then fluorescence is measured. -Then, results are relayed to Dr. who then tells the patient. of test results.
•A ribosome has three binding sites for tRNA
-The A site holds the activated tRNA that carries the next amino acid to be added to the chain -The P site holds the tRNA that carries the lengthening polypeptide chain -The E site is the exit site, where discharged tRNAs leave the ribosome
Human Genome Size
-The human genome is 3 bill. bases long. -The sequence would take up 69,900 double pages of The NY Times. -If you printed the human genome in 12 font & stretched it out, it would run all the way from NYC to LA. -23 pairs of chromosomes ranging in size from 246,122,627 pairs-Chrome 1. 44,626,493 base pairs -Chrome 21
The Flow of Genetic Information
-The information content of genes is in the specific sequences of nucleotides. -The DNA inherited by an organism leads tospecific traits by dictating the synthesis of proteins Proteins are the links between genotype and phenotype. -Gene expression, the process by which DNA directs protein synthesis, includes two stages: transcription and translation.
Controversial Topics
-The most important thing an individual in society can do today is to study & take an informed, intelligent position on the argument-- -Science Course presents Evolution, a Theology Course may be present Intelligent Design.
Crossing Over & Random Alignment
-There are millions of possible combinations of genes that each parent can produce because of : -Crossing over & Random alignment of homologous pairs (or random assortment of pairs)
Sex-Linked Traits
-Traits that are influenced by genes carried on the sex chromosomes. EXAMPLE: Colorblindness is a recessive trait.
Natural Selection
-Traits that were detrimental for an animal would be eliminated by the failure of the animal containing them to reproduce. -Darwin had no knowledge of modern genetic concepts & therefore had no knowledge of the genetic principles that are the basis of evolutionary theory as it exists today. "What Darwin Never Knew"
Multiple Alleles....cont'd
-Two genes, one carried on each chromosome of a homologous pair, determine traits in one individual. -A population may have many different alleles with the potential to contribute to the phenotype of any member of the population - Multiple Alleles.
Crossing Over
-When the homologous pairs are in Meiosis I, they can exchange genetic info in the process of crossing over. --Homologous Chromosomes comes into direct contact and actually "swap" sections of DNA. --This introduces new combinations of paternal & maternal traits (alleles) for next generation.
Random Alignment
-When the homologous pairs line up during metaphase I of meiosis, the way the homologs place themselves is random, so is called random alignment. -No predicting which member of any given homologous pair will go in which direction (to which pole) -As long as one from each pair gets to each pole, variability of combinations does not matter.
Woodrats are medium sized rodents with lots of interesting behaviors. You may know them as packrats. Let's assume that the trait of bringing home shiny objects (H) is controlled by a single gene and is dominant to the trait of carrying home only dull objects (h). If two heterozygous individuals are crossed, what are the potential genotypes of their offspring?
1 of HH, 2 of Hh, 1 of hh
Modern Summary of Darwin's Theory
1. All organisms have far greater reproductive potential that is ever realized. --Female oyster releases 100,000 eggs/season. --Female sea star releases 1 mill. eggs/season. 2. Inherited variations exist. --Arise from a variety of sources including mutation, genetic recombination, & random fertilization. --Seldom are any two individuals exactly alike. --Genetic variations may be advantageous, harmful, or neutral. --These variations can be passed on to offspring. 3. Bc resources are limited, existence is a constant struggle. --Many more offspring are produced than resources can support. --The individuals that die are those with traits (variations) that make survival & successful reproduction less likely. --Traits that promote successful reproduction are said to be adaptive. 4. Adaptive traits become more common in subsequent generations: curve in the road. --Organisms with maladaptive traits are less likely to reproduce, so the maladaptive traits become less frequent in a population: or leads to extinction.
Three primary sources of genetic variation:
1. Mutations are changes in the DNA. A single mutation can have a large effect, but in many cases, evolutionary change is based on the accumulation of many mutations. 2. Gene flow is any movement of genes from one population to another & is more important source of genetic variation. 3. Sexual reproduction can introduce new gene combinations into a pop. The genetic shuffling is another important sources of genetic variation.
Supposing brown eyes in people (B) is dominant to blue (b). Could a marriage between two blue-eyed people produce a brown-eyed child? Could a marriage between a homozygous brown-eyed person and a blue-eyed person result in blue-eyed children? Could two brown-eyed people have a blue-eyed child? Explain all of your answers by supplying the proper symbols.
1. only bb child, NO brown eyes possible 2. Only Bb child, so NO blue-eyes possible 3. Yes, could have blue-eyed child (bb) if both parents are heterozygous (Bb)
Gregor Mendel
1822-1884
Genome engineering is actually not new, it's been in development since the _____.
1970s.
Mendel's law of Inheritance
1st law: Principle of Segregation 2nd law: Independent Assortment
Dihybrid Crosses=
=A cross that shows the possible offspring for two traits.
Oogenesis=
=Ovum formation by meiosis. -In contrast to the male, all the human female "starter cells" (primary germ cell or Oogonium) have already progressed to stage of Prophase in Meiosis I while still in fetus. -Primary oocyte held in "suspended animation" or "arrested in development" at time of birth. -Beginning at puberty, remaining Primary oocytes will respond to hormone signals (may take up to 40+ years) So continue to progress in Meiosis, completing in Meiosis I, beginning in Meiosis II.
Spermatogenesis=
=Sperm formation by meiosis & maturation. -Meiosis occurs only after puberty. -The entire process of formation & maturation (differentiation) of sperm takes about 70 days, producing 200 million/day. -Each "starter cell" (primordial germ cell or spermatogonium) produces 4 Spermatids by Meiosis, & also replenishes the "started cells" by Mitosis. -Sperm cells mature through process called differentiation.
RNA bases:
A U G C How many ways can these four bases be arranged into codons? (3 bases)? 64! 61 for Amino acids & 3 code for an end chain (stop codon)
Blood can only be donated from a person with a specific ABO antigen to a person without antibodies for that antigen. Otherwise, agglutination (clumping) will occur.
A cannot donate to B or O bc they have anti-A antibodies. B cannot donate to A or O bc they have anti-B antibodies. AB cannone donated to A bc they have anti-B antibodies or B bc they have anti-A antibodies. O can potentially donate to everyone bc their blood have no antigen to attack. Type O should first have its own anti-A & anti-B antibodies removed. Rh+ blood should not be transfused to an Rh- person, however Rh- blood can be donated to an Rh+ person.
Inversion
A chromosomal fragment may also reattach to the original chromosome but in the reverse orientation, producing an inversion.
Monohybrid cross
A cross between individuals that involves one pair of contrasting traits
dihybrid cross
A cross between two individuals, concentrating on two definable traits Phenotype ratio: 9 black, Rough: 3 black, smooth: 3 white, Rough: 1 white, smooth Genotype ratio: 1BBRR: 2BBRr: 2BbRR: 4BbRr: 1BBrr: 2Bbrr: 1bbRR: 2bbRr: 1bbrr
Translocation
A fourth possible result of chromosomal breakage is for the fragment to join a non-homologous chromosome, a rearrangement called a translocation.
DNA Sequencing
A gene's complete nucleotide sequence can be determined using a process called DNA sequencing. In the last 15 years, "next-gen. sequencing" techniques have been developed the are incredibly fast. For ex: 1980s - 1,000 base pairs/day 2000- 1,000 base pairs/second. 2016- 25 million base pairs/second. Newer technique claims it will do 66 million per second.
Karyotype
A picture of all the chromosomes in a cell arranged in pairs
Gene
A segment of DNA on a chromosome that codes for a specific trait
Locus
A specific place along the length of a chromosome where a given gene is located.
Blood Types
A, B, AB, O
Two blood groups (ABO and Rh)
ABO blood group: • has 4 blood types (phenotypes) • has 2 different types of molecules (carbohydrates) found on the surface of Red blood cells, named A and B
Red blood cell membranes contain glycoproteins & glycolipids that determine your ABO blood type & proteins that determine you Rh (+/-) blood type.
ABO blood type is determined by the presence of A, B, both (AB) or neither (O) of the A or B antigens. Rh blood type is determined by the presence of (+) or lack of (-) the D antigen.
Normal vision in man is dominant to color-blindness and the alleles are on the X chromosome. A normal man whose father was color-blind marries a color-blind woman. What would be the chance of their sons and daughters being color-blind?
All sons are colorblind All daughters have normal vision but are carriers (heterozygous)
Imagine that a newly discovered, recessively inherited disease is expressed only in individuals with type O blood, although the disease and blood group are independently inherited. A normal man with type A blood and a normal woman with type B blood have already had one child with the disease. The woman is now pregnant for a second time. What is the probability that the second child will also have the disease? Assume that both parents are heterozygous for the "disease" gene.
Already have one child with disease, which means that the child is i i , so parents must be heterozygous 1 in 4 chance of ii, so1 in 4 chance of disease (25%)
Recessive
An allele that is masked when a dominant allele is present
Homozygous & Heterozygous
An animal is homozygous if it carries two identical alleles for a given trait. - TT or tt An animal is heterozygous if the alleles of a gene are different. - Tt
woolly mammoth
An extinct organism whose genome was sequenced using mummified remains.
Klinefelter syndrome
An extra X chromosome in a male, producing XXY, occurs approximately once in every 500 to 1,000 live male births. Have male sex organs, but the testes are abnormally small & the man is sterile.
Heterozygous
An organism that has two different alleles for a trait
Homozygous
An organism that has two identical alleles for a trait
Somatic Cells
Any cells in the body other than reproductive cells.
Autosomes
Any chromosome that is not a sex chromosome.
Hydrogen bonds between ___________ will hold the two strands of a DNA molecule together.
B.) Nitrogenous bases on each strand.
The instructions for the traits of an organisms are determined by:
B.) The order of nucleotides in DNA molecules.
What are the chemical components of a DNA nucleotide?
B.) a phosphate, a sugar, & a nitrogenous base
Even before the structure of DNA was solved, studies indicated that the genetic material must have the following properties: -Be able to store information: -Be faithfully replicated and be passed on from generation to generation: -Allow for changes, and thus evolution, to occur:
BE ABLE TO STORE INFORMATION: Information is stored by the sequence of the bases. BE FAITHFULLY REPLICATED & BE PASSED ON FROM GENERATION TO GENERATION: By separating the two chains, you can then make new comp. copy by obeying the pairing rules. ALLOW FOR CHANGES, & THUS EVOLUTION TO OCCUR: Mutations occur when the the sequence is changed.
__________ is the manipulation of organisms or their components to make useful products.
Biotechnology
Incomplete Dominance
Blending of Traits EX: CR= RED CW=WHITE CRCR=RED CRCW=PINK CWCW=WHITE
The blood type plasma may also contain antibodies, depending on the ABO & Rh blood types.
Blood type A, have anti-B antibodies. Blood type B, have anti-A antibodies. Blood type O, have both anti-A and antibodies & anti-B antibodies. Blood type AB, will not have any anti-A nor anti-B antibodies. No one has anti-D (Rh) antibodies unless they are Rh- & have been previously exposed to Rh+ blood.
Co Dominance
Both alleles affect the phenotype in separate, distinguishable ways. No blending or intermediate character, rather both alleles are expressed distinctly at the same time.
2nd law: Independent Assortment
By the law of independent assortment, each pair of alleles segregates into gametes independently. (we now know this is because each pair of homologous chromosomes is independent of the next: maternal and paternal chromosomes for each homologous pair can sort in either direction) To test this law a Dihybrid Cross is used & a phenotype ratio of 9:3:3:1
1st law: principle of segregation
By the law of segregation, the two alleles for a character are packaged into separate gametes To test this law a Monohybrid Cross is used & a phenotype ratio of 3:1
Sex chromosomes
Chromosomes that determine the sex of an individual
CRISPR stands for:
Clustered Regularly Interspaced Short Palindromic Repeats
Ifa particular sequence of bases in one strand of DNA is 5' AGT 3', then the other sequence of DNA on the opposite strand is:
D.) 3' TCA 5' Antiparallel chains
In 1928, Frederick Griffith conducted an experiment in which he injected mice with different kinds of bacteria. When bacteria that cause disease (pathogenic) were injected in healthy mice, these mice got sick and died. Other types of bacteria (non-pathogenic) did not cause the mice to die. Griffith took the DNA from dead pathogenic bacteria and transferred it into living non-pathogenic bacteria. These altered bacteria were then injected into healthy mice. The mice died of the same disease caused by the pathogenic bacteria. Based on this information, which statement would be a valid conclusion?
D.) When DNA from one organism is transferred to another organism, it can give new traits to the second organism.
Meiosis versus mitosis
DNA replication: Occurs during interphase before meiosis I but not meiosis II. # of divisions: Two, each including prophase, metaphase, anaphase, & telophase. Synapsis of homo. chromosomes: Occurs during prophase I along with crossing over between non sister chromatids; resulting chiasmata hold pairs together due to sister chromatid cohesion. # of daughter cells & genetic composition: Four, each haploid (n); genetically different from the parent cell & from each other. Role in animals, fungi, & plants: Produces gametes (in animals) or spores (in fungi & in plant sporophytes); reduces # of chromosome sets by half & introduces genetic variability amount the gametes or spores.
Mitosis versus Meiosis
DNA replication: Occurs during interphase, before mitosis begins. # of divisions: One, including prophase, prometaphase, metaphase, anaphase, & telophase. Synapsis of homo. chromosomes: Does not occur. # of daughter cells & genetic composition: Two, each genetically identical to the parent cell, with the same # of chromosomes. Role in animals, fungi, & plants: Enables multicellular animal, fungus, or plant to arise from a single cell; produces cells for growth, repair, & in some species, asexual reproduction; produces gametes in the plant gametophyte.
Ebony body fruit fly:
Dark brown, long wings, red eyes.
Dominant
Describes a trait that covers over, or dominates, another form of that trait.
Domestic dogs=
Diestrous, not necessarily "seasonal"
The Kakapo Bird in the movie Animal Misfits....now considers the ______ bird.
Dodo
Genotype examples:
Dominant allele EXAMPLE: A Recessive allele EXAMPLE: a
The results of Mendel's F1, Crosses for Seven Characters in Pea Plants
Each character is determined by one gene for which there are only two alleles that "code" for 2 traits.
Long-day breeders:
Examples horses, hamsters, & ferrets are sexually active in spring & summer.
Short-day breeders (length or daylight):
Examples sheep, goats, deer, elk, chinchillas) are sexually active in fall or winter/into spring.
A brown mink mated with a silver-blue mink, producing all brown offspring. When these F1 mink were crossed among themselves, they produced 47 brown animals and 15 silver-blue animals (F2 generation). Determine all the genotypes and phenotypes, and their relative ratios, in the F1 and F2 generations.
F1 generation- Bb x Bb F2 generation- This is a 3:1 Phenotypic Ratio of brown:blue Exact Genotypic Ratio from a Punnett would be "1BB : 2Bb : 1bb"
Homozygous dominant: Homozygous recessive: Heterozygous:
GG gg Gg
Other Evolutionary Mechanisms: Gene Flow
Gene Flow -Changes in relative allele frequencies from the migration of individuals -Could increase genetic variation.
Pleiotropy
Genes can have multiple phenotypic effects from one gene, this is called pleiotropy. For example, pleiotropic alleles are responsible for the multiple symptoms of certain hereditary diseases, such as cystic fibrosis & sickle-cell disease.
_________ is the direct manipulation of genes for practical purposes.
Genetic engineering
Barriers that prevent mating: Postzygotic Barriers
Horse + Donkey = Mule. horse: (2n=64, n=32) donkey: (2n=62, n=31) mule: (2n=63, n= not possible)
Sex-linked Inheritance
Humans have 23 pairs of chromosomes 22 pair are Autosomes 1 pair are sex Chromosomes Involves genes located on the sex chromosomes. (usually the X chromosome) Ex. XA Xa or Xa Y If "a" is recessive & codes for color-blindness Then: XᴬXᴬ and XᴬXᵃ and XᴬY are normal vision XᵃXᵃ and XᵃY are color blind
Aneuploidy
If either of the aberrant gametes unites with a normal one at fertilization, the zygote will also have an abnormal number of a particular chromosome.
Oogenesis versus Spermatogenis
In humans, the production of ova (plural for ovum) & sperm cells differ in several ways: -Supply of females egg precursor cells is limited, versus -Supply of sperm precursor cells in males constantly replenishes itself. -Usually one one mature egg (ovum) per normal 28 day menstrual cycle in females, versus - male produces about 200 million sperm every day!
Sepia eyes fruit fly:
Light brown, long wings, dark brown eyes.
white-eyed fruit fly:
Light brown, long wings, white eyes.
meiosis in animal cell
Meiosis I diagram -->
meiosis in animal cell...cont'd
Meiosis II diagram-->
Nondisjunction
Members of a pair o homologous chromosomes do not move apart properly during meiosis 1 or sister chromatids fail to separate during meiosis 2.
Turner syndrome
Monosomy X, which is called Turner syndrome, occurs about once in every 2,500 female births & is the only known viable monosomy in humans. Although these XO individuals are phenotypically female, they are sterile because their sex organs do not mature.
Multiple Alleles & Co dominance
More than 2 alleles for a single gene Genes often exist in a population in more than two allele forms. Example = Blood Groups in humans
Seasonally polyestrous animals or seasonal breeders:
More than one estrous cycle during a specific time of the year and can be divided into short-day and long-day breeders. The timing of estrus=often coordinated with seasonal availability of food and other circumstances such as migration, predation etc., the goal being to maximize the offsprings chances of survival. Animal Husbandry= science of breeding & caring for farm animals.
In humans, the ABO blood group is inherited by a single gene (I) with three alleles. The alleles are IA, IB and i. The alleles produce the blood groups A, B, AB and O. Genotypes and phenotypes are: IAIA or IAi = type A IBIB or IBi = type B IAIB = type ABii = type O The Rh factor of blood is inherited by a separate gene with two alleles. The dominant allele (D) produces Rh positive blood, and the recessive allele (d) produces Rh negative blood. A woman with type A negative blood gives birth to a baby with type AB positive blood. Could the father be a man with type O negative blood? Why or why not?
No, because baby would have to be D__ (where would the dominant D come from) and the baby could not have received IB from an O father.
Down Syndrome
One aneuploid condition. Down syndrome affects approximately one out of every 830 children born in the United States. Down syndrome is usually the result of an extra chromosome 21, so that each body cell has a total of 47 chromosomes. Down syndrome is often called trisomy 21.
How to report results:
PHENOTYPE ratio: Expresses the results of a cross according to the relative numbers of offspring in each visually distinct class (3 can roll tongue : 1 cannot roll tongue) GENOTYPE ratio: Expresses the results of a cross according to the relative numbers of progeny in each genotype category (1TT : 2Tt : 1tt)
Brown (BB) mouse x White (bb) mouse
Phenotype ratio: brown 4 : 0 white Genotype ratio: 4 Bb
Phenotype
Physical expression of the gene, Represents an organisms physical traits.
Types of Small-Scale Mutations
Point mutations within a gene can be divided into two general categories -Substitutions -Insertions & deletions
Polygenic Inheritance
Polygenic inheritance, an effect of two or more genes on a single phenotype. Skin color in humans is an example of polygenic inheritance.
Scientist use a laboratory technique called _____________ or ____. The goal of this reaction is to amplify a small amount of viral genetic material so that it can be detected.
Polymerase chain reaction or PCR
Reproductive Isolation
Pre- or Post- zygotic
The Munchkin cat or Sausage cat is a newer breed of cat characterized by its very short legs, which are caused by a genetic mutation for dwarfism.
Questionable health issues associated with the condition. The munchkin gene is autosomal dominant. Homozygous embryos for the munchkin gene are not viable, and do not develop in the womb. Only kittens that are heterozygous for the munchkin gene develop into viable short legged munchkin kittens. The mating of two munchkin parents, Mm x Mm, have the chance of producing these offspring: 25% MM- a nonviable kitten, 50% Mm-short-legged, 25% mm- normal. The resulting litter will be 2/3 Mm-short-legged and 1/3 mm-normal.
Blood types are determined by the antigens that are present on the surface of red blood cells .
RBCs, also known as erythrocytes.
Rh blood group:
Rhesus monkey name origin Has only 2 alleles, Rh+ = D Rh- = d Has 1 type of molecule on surface of RBC, or the molecule is absent (Rh-) Rh+ is more common then Rh- Most common blood type is Type O+
Populations & Speciation
SELECTION: can be a major force driving allele frequency change, and leads to adaptation MUTATION: creates new alleles in a gene pool. MIGRATION: gene flow from other populations can alter allele frequencies. GENETIC DRIFT: causes random changes in allele frequency especially in small populations.
Meiosis...cont'd.
Since there are two separations we end up with four cells. Notice that the gametes are haploid- having one chromosome from each homologous pair. Each gamete carries half the genetic info as the parent.
Differentiating Sex in Fruit Flies
Size: females are longer. Abdomen: females more pointed; males more rounded. Abdomen color: males have black-tipped. Sex combs on front legs: Males have them; not females.
Another Evolutionary Mechanism: Speciation
Speciation is the formation of the new species. -Requires that subpopulations are prevented from interbreeding--Reproductive isolation.
Diestrous=
Species that go into heat twice per year.
Monoestrous=
Species, such as bears, foxes, & wolves, have only one breeding season per year, typically in spring to allow growth of the offspring during the warm season to aid survival during the next winter.
The key to PCR is an unusual, heat-stable DNA polymerase called __________.
Taq polymerase. Named after the microorganim Thermus aquatics, from which it was originally isolated-which thrives in hot springs & thermal vents at 180 degrees far. PCR using primers specific for the sequence to be amplified (these are some of the chemical Reagan's in short supply for COVID testing)
Duplication
The "deleted" fragment may become attached as an extra segment to a sister or non sister chromatid, producing a duplication of a portion of that chromosome.
Darwin's experiences in South America & _______________ Islands (1831-1836) convinced him that animals change over time. Published in _____.
The Galapagos 1859
Genotype
The genetic makeup of an organism. "what genes look like" (represented by a pair of letters that corresponds to a pair of alleles)
A boy, whose parents and grandparents had normal vision, is color-blind. Give the genotypes for his mother and his maternal grandparents.
The genotype of boy's mother would be XAXa (she was a carrier) The genotype of the boy's maternal grandmother would be XAXa (she was also a carrier). The genotype of the boy's maternal grandfather would be XAY.
Populations & Gene Pools...contd.
The potential for genetic variation in individuals of a population is virtually unlimited. -Sexual reproduction results in constant allele shuffling. -This allele shuffling & the interaction of resulting phenotypes with the environment have one of two consequences for the population: --Relative freq. of alleles change across generations. --Relative freq. remain fairly constant.
Genetics
The study of how biological information is transmitted from one generation to the next. Information carried in DNA is expressed int the kinds of proteins that exist in each individual. -Proteins --Contribute to observable traits: eye color, hair texture. --Function as enzymes that regulate the rates of chemical reactions in organisms. Other protein functions (contraction, transport, some hormones, antibodies, cell membrane receptors, blood clotting, body fluid regulation with albumin)
Phenotype & Genotype
The visual expression of the allele is the phenotype. The genetic makeup is the genotype. -Can roll tongue= TT or Tt -Can't roll tongue = tt
Meiosis...cont'd.
There are 22 pairs of autosomes (non-sex chromosomes) -There is one pair of sex chromosomes: males have one X and one Y chromosome. females have two Y chromosomes. -The pairs of chromosomes (homologous pairs) carry the same genes.
Meiosis I
There are four phases in meiosis I: -Prophase I: homologous pairs come together -(possible crossing over) -Metaphase I: the homologous pairs line up at the equator- (random assortment occurs) -Anaphase I: the homologous pairs separate. -Telophase I: nuclear envelopes reform.
Meiosis II
There are four phases in meiosis II: 1. Prophase II: Nuclear envelopes disappear. 2. Metaphase II: Chromosomes line up at cell equator. 3. Anaphase II: Sister chromatids separate. 4.Telophase II: Nuclear envelopes reform.
The image on the lower left shows the famous Photo 51 taken in May 1952 by Rosalind Franklin and her student, Raymond Gosling. This x-ray diffraction pattern provides information about the positions of atoms in a DNA molecule. Measurements revealed that the distance between the two strands was always equal. -Explain how this information helped Watson and Crick build a successful model of DNA.
They noticed the picture made an "X", which is a helix, double-helix. The 2 backbones has to run in opposite directions which led him to conclude that the sugar phosphate backbones has to be on the outside with the bases on the inside.
Faulty instructions for making an enzyme called tyrosinase.
This enzyme is located in melanocytes, which are specialized cells that produce a pigment called melanin. Melanin is the substance that gives skin, hair, and eyes their color.
Examples of Co dominance in Chickens
When a chicken with white feathers breeds with a chicken with black feathers, the result is an offspring chicken that grows up to have both black and white feathers.
Epistasis
When a gene at a locus alters the phenotype expression of a gene at a second locus.
Fruit fly terms:
Wild type: Mutant: Genotype: Phenotype: Phenotype is a characteristic of an organism that can be observed and measured.
In humans, the ABO blood group is inherited by a single gene (I) with three alleles. The alleles are IA, IB and i. The alleles produce the blood groups A, B, AB and O. Genotypes and phenotypes are: IAIA or IAi = type A IBIB or IBi = type B IAIB = type ABii = type O The Rh factor of blood is inherited by a separate gene with two alleles. The dominant allele (D) produces Rh positive blood, and the recessive allele (d) produces Rh negative blood. A woman with type B positive blood gives birth to a baby with type O negative blood. She claims that the father is a man with type A negative blood. Based on the blood type information, could he be the father? Why or why not?
Yes, if both woman and suspect father are heterozygous for ABO blood group, and if mother is heterozygous for Rh factor.
Deletion
a deletion occurs when a chromosomal fragment is lost.
Dihybrid cross:
a mating between organisms that have different alleles for two genes of interest. Long wings for fruit fly: (L) which is dominant to the allele short wing (l). Brown body (B) is dominant to the allele for ebony body (b).
The lubber grasshopper is a very large grasshopper, and is black with red and yellow stripes. Assume that red stripes are expressed from the homozygous SRSR genotype, yellow stripes from the homozygous SrSr genotype, r and both from the heterozygous genotype SRS . a) What will be the phenotypic ratio of the F1 generation resulting from a cross of two grasshoppers, both with red and yellow stripes? That is, what will be the ratio of "red : both : yellow" b) What phenotypes would be produced by crossing a grasshopper with both color stripes and one with red stripes?
a) 1SRSR : 2SRSr : 1SrSr1 red : 2 both : 1 yellow b) 2 red = 50% red 2 both = 50% both
In tigers, a recessive allele causes an absence of fur pigmentation (a "white tiger") and a different recessive allele causes a cross-eyed condition (two separate traits). If two phenotypically normal tigers that are heterozygous for both traits are mated: a) What percentage of their offspring will be cross-eyed? b) What percentage of their offspring will be white and have normal vision?
a) __ __ n n = crossed-eyes = 4/16 = 25% b) f f N __ = white fur, normal eyes = 3/16 = 18.75%
Woodrats are medium sized rodents with lots of interesting behaviors. You may know them as packrats. Let's assume that the trait of bringing home shiny objects (H) is controlled by a single gene and is dominance to the trait of carrying home only dull objects (h). Suppose two heterozygous individuals are crossed. a) How many of each genotype would be expected if only four offspring were produced? b) How many of each phenotype would be expected if only four offspring were produced?
a) oneHH : TwoHh : one hh b)Phenotype ratio 3 shiny : 1 dull
In the 1950s when Watson and Crick were working on their model of DNA, many scientists did not think that DNA carried the genetic code. a) What was the other type of molecule that some scientists thought might carry genetic information? b) Why did this other type of molecule seem like a likely candidate?
a)protein b) There are a lot of different kinds of them & they do a lot of different stuff inside the cell.
Scientists build models based on what they know from previous research to derive testable hypotheses. Independently, both Watson and Crick and their competitor Linus Pauling constructed an incorrect triple-helix model with the nitrogenous bases arranged so they were on the exterior of the molecule and the phosphate groups on the interior. a) Although their model was wrong, what assumption made it reasonable to build a model with the bases projecting to the outside? b) What evidence caused Watson and Crick to revise their model?
a.) Because the base contained genetic information & why hid that. b.)Watson has misremembered some key measurements from Franklins work.
The finches of the Galapagos Islands provide an example of ______ _______.
adaptive radiation The formation of new forms from an ancestral species, usually response to the opening of new habitats.
Homologous chromosomes have __________.
alleles (alternate versions) of a gene at the same locus (one is paternal origin, other is maternal origin).
three types of sexual life cycles
animals, plants & some algae, most fungi & some protists.
Hybrids
are the offspring of two different purebred varieties: -The parental plants are the P generation. -Their hybrid offspring are the F1 generation. -A cross of the F1 plants forms the F2 generation.
Eye color in humans: At least two pairs of genes control eye color. Both pairs influence the production of the pigment melanin, but act independently. One pair of alleles is B (Brown color; dominant) and b (blue color); the other pair is A (pigment production; dominant) and a (no pigment production; albino). The gene pair aa is epistatic to (masks) B and b and produces the nonpigmented eyes of the albino. -What are the phenotypes for each of the following genotyped individuals: -Give the genotypes and phenotypes of the possible offspring of the mating
bbAa bb = blue pigment, Aa = production of pigment so bbAa = blue eyed Bbaa Bb = brown pigment, aa = epistatic, so no production of pigment, so Bbaa = albino (no color) 1 brown : 1 blue : 2 no color (albino) due to epistasis by aa BbAa = brown bbAa = blue Bbaa = albino Bbaa = albino
Albinism in about 1/10,000 births (autosomal recessive gene),
but odds of seeing in wild much lower (selection against the mutation: predators, abandonment, sensitivity to light, etc.)
Male calicoes
can happen when a male cat has two X chromosomes.
Mutations
changed in the genetic material of a cell.
Point mutations
chemical changes in just one base pair of a gene.
Dominant alleles hide the expression of another allele.
dark hair, curly hair, brown eyes, widows peak, dimples, unattached earlobes, freckles, broad lips.
A wild-type fruit fly:
exhibits the most common phenotype in the population. Light brown, long wings, & red eyes.
sex-linked gene
gene located on the X or Y chromosome
In fruit flies (Drosophila melanogaster) red-eye is dominant to pink-eye. By crossing a heterozygous red-eyed male fly to a pink-eyed female fly, 60 offspring were produced. How many would you expect to be red-eyed and how many pink-eyed?
half (50%) = 30 are Rr = red-eyed half (50%) = 30 are rr = pink-eyed
Eight breeds of dogs (all members of the same species), the results of ____________________ of years of artificial selection.
hundreds to thousands
Agglutination
in blood typing is the clumping of red blood cells caused by antibodies binding to the antigens on the surfaces of red blood cells.
A few mammalian species, such as rabbits, do not have an estrous cycle, instead being _____________.
induced to ovulate by the act of mating and are able to conceive at almost any arbitrary moment.
Red-green colorblindness
is a common human sex-linked disorder and caused by a malfunction of light-sensitive cells in the eyes.
Character
is a heritable feature that varies among individuals (determined by a gene or multiple genes)
Gene locus
is a specific location of a gene along a chromosome.
Trait
is a variant of a character (different alleles for single gene).
Trisomy 21
is another name for Down syndrome. Because the cells are trisomic for chromosome 21.
Short wind fruit fly:
light brown, short wings, red eyes.
Recessive alleles are those whose expression can be masked.
light hair, straight hair, light eyes (blue, etc), straight hairline, no dimples, attached earlobes, no freckles, thin lips.
Types of Crosses:
monohybrid and dihybrid.
Adaptive mutations ______ occur as a result of a _____, and there is no guarantee that a species will change in order to meet the challenges of a changing environment.
never, need If adaptive changed did occur in response to need, extinction would not occur.
"Survival of the fittest"
not really about strength or power unless it means more successful offspring. It's really more about "success in love" than its is about "strength or physical fitness"
Adaptation
occurs when a heritable change in a phenotype increases an animals chances of successful reproduction in a specific environment. -must be heritable. -may be behavioral, physiological, or morphological (eg color fur) -arise as a result of mutations, and are perpetuated by natural selection.
Allele
one of a number of different forms of a gene.
Gonads
ovaries and testes (sex organs)
CRISPR-Cas9
pronounced crisper
Schematic ribosome model
showing binding sites---->
Five different species of canines, the results of __________ of years of natural selection.
thousands to millions
Molecular Components of Translation
•A cell translates the mRNA codons into protein with the help of transfer RNA (tRNA) and ribosomal RNA (rRNA or ribosome) •tRNA (has anti-codon site that matches up with the codon sites of mRNA, plus has a site for attachment to correct Amino acid) = transfer amino acids to the growing polypeptide at the ribosome
Substitutions
•A nucleotide-pair substitution replaces one nucleotide and its partner with another pair of nucleotides which can result in: Silent mutations have no effect on the amino acid produced by a codon because of redundancy in the genetic code Missense mutations still code for an amino acid, but not the correct amino acid Nonsense mutations change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein.
Pedigree Analysis
•A pedigree is a family tree that describes the interrelationships of parents and children across generations •Inheritance patterns of particular traits can be traced and described using pedigrees
Linked Genes
•Are genes that are found on the same chromosome (tend to be inherited together). •genes for eye, skin, and hair color are tightly "linked", meaning that they're usually all inherited together. This is why people typically have either all light features, or all dark features. •Linked genes are found close together on a chromosome (loci are near each other), so are less likely to be separated by crossing over (recombination) during Meiosis I
CRISPR-Cas9
•CRISPR-Cas9 is a unique technology that enables geneticists and medical researchers to edit parts of the genome by removing, adding or altering sections of the DNA sequence. •Method for "molecular scissors" discovered while working with immune "systems" of bacteria (bacteria fighting against invasions by viruses). •It is currently the simplest, most versatile and precise method of genetic manipulation and development of gene therapy.
Degrees of Dominance
•Complete dominance - the phenotypes of a heterozygote and a homozygous dominant are indistinguishable •Incomplete dominance - neither allele is completely dominant, the heterozygous phenotype shows a "mix/blend" of traits • •Co dominance - the two alleles both affect the phenotype in separate, distinguishable ways.
Crossing Over
•Crossing over between homologous chromosomes produces recombinant chromosomes, which combine DNA inherited from each parent •Crossing over contributes to genetic variation by combining DNA from two parents into a single chromosome •In humans, an average of one to three crossover events occurs per chromosome
Elongation of the Polypeptide Chain
•During elongation, amino acids are added one by one •Each addition involves enzymes called "elongation factors" and occurs in three steps: codon recognition, peptide bond formation, and translocation (ribosome must move further down the mRNA, in the direction towards 3') •Energy expenditure (ATP is used) in process
Translation is the RNA-directed synthesis of a polypeptide
•Genetic information flows from mRNA to protein through the process of translation
Independent Assortment of Chromosomes
•Homologous pairs of chromosomes orient randomly at metaphase I of meiosis •In independent assortment, each pair of chromosomes sorts maternal and paternal homologs into daughter cells independently of the other pairs
Many human traits follow Mendelian patterns of inheritance
•Humans are not good subjects for genetic research -Generation time is too long -Parents produce relatively few offspring -Breeding experiments are unacceptable •However, basic Mendelian genetics endures as the foundation of human genetics
Extending Mendelian Genetics for a Single Gene
•Inheritance of characters by a single gene may deviate from simple Mendelian patterns in the following situations: -When alleles are not completely dominant or recessive -When a gene has more than two alleles -When a gene produces multiple phenotypes
Insertions & Deletions
•Insertions and deletions are additions or losses of nucleotide pairs in a gene •These mutations have a disastrous effect on the resulting protein more often than substitutions do •Insertion or deletion of nucleotides may alter the reading frame, producing a frameshift mutation
Making Multiple Polypeptides
•Multiple ribosomes can translate a single mRNA simultaneously, forming a polyribosome •Polyribosomes enable a cell to make many copies of a polypeptide very quickly
Mutagens
•Mutations may result from •errors in DNA replication or recombination or •physical or chemical agents called mutagens. •Mutations •May be neutral •are often harmful but •are useful in nature and the laboratory as a source of genetic diversity, which makes evolution by natural selection possible.
Basic Principles of Transcription and Translation
•RNA is the bridge between genes and the proteins for which they code •Transcription is the synthesis of RNA using information in DNA •Transcription produces messenger RNA (mRNA) •Translation is the synthesis of a polypeptide, (protein) using information in the mRNA •Ribosomes are the sites of translation
Random Fertilization
•Random fertilization adds to genetic variation because any sperm can fuse with any ovum (unfertilized egg) •The fusion of two gametes (each with 8.4 million possible chromosome combinations from independent assortment) produces a zygote with any of about 70 trillion diploid combinations
Termination of Translation
•Termination occurs when a stop codon in the mRNA reaches the A site of the ribosome •The A site accepts a protein called a release factor •The release factor causes the addition of a water molecule instead of an amino acid •This reaction releases the polypeptide, and the translation assembly comes apart
Sexual Reproduction
•The behavior of chromosomes during meiosis and fertilization is responsible for most of the variation that arises in each generation •Three mechanisms contribute to genetic variation: -Independent assortment of chromosomes -Crossing over -Random fertilization
Evolution of the Genetic Code
•The genetic code is nearly universal, shared by the simplest bacteria to the most complex animals •Genes can be transcribed and translated after being transplanted from one species to another
Polymerase Chain Reaction
•The polymerase chain reaction, PCR, can produce many copies of a specific target segment of DNA •A three-step cycle—heating, cooling, and replication—brings about a chain reaction that produces an exponentially growing population of identical DNA molecules.
Inheritance patterns are often more complex than predicted by simple Mendelian genetics
•The relationship between genotype and phenotype is rarely as simple as in the pea plant characters Mendel studied •Many heritable characters are not determined by only one gene with two alleles •However, the basic principles of segregation and independent assortment apply even to more complex patterns of inheritance
Targeting Polypeptides to Specific Locations
•Two populations of ribosomes are evident in cells: free ribosomes (in the cytosol) and bound ribosomes (attached to the ER) •Free ribosomes mostly synthesize proteins that function in the cytoplasm •Bound ribosomes make proteins of the membrane system and proteins that are secreted from the cell •Ribosomes are identical and can switch from free to bound
