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238 Cards in this Set
- Front
- Back
What were the seed traits in Mendel's experiments on peas?
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Seed color: yellow or green
Seed shape: round or wrinkled Seed coat color: gray or white |
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What were the pod traits in Mendel's experiments on peas?
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Pod color: yellow or green
Pod shape: inflated or constricted |
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What two things did Mendel's monohybrid (single trait) crosses reveal?
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1) The concept of dominance - F1 hybrid progeny were not intermediate, but resembled one parent
2) Mendel's First Law: Segregation of Alleles |
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Mendel's first law
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Segregation of Alleles:
- Each individual has two alleles encoding a trait - The two alleles separate when gametes are formed - Alleles separate in equal proportions |
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Gene
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A genetic factor (region of DNA) that helps determine a characteristic
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Allele
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One of two or more alternate forms of a gene
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Locus
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Specific place on a chromosome occupied by an allele
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Genotype
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Set of alleles possessed by an individual organism
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Heterozygote
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An individual organism possessing two different alleles at a locus
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Homozygote
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An individual organism possessing two of the same alleles at a locus
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Phenotype
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The appearance or manifestation of a character
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Character or characteristic
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An attribute or feature
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Genotypic ratio for an Aa x Aa cross
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1:2:1 AA:Aa:aa
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Genotypic ratio for an Aa x aa or an Aa x AA cross
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1:1 AA:Aa
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Genotypic ratio for an AA x AA, aa x aa, or AA x aa cross
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Uniform progeny: All AA, all aa, or all Aa
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What is a chi-squared test?
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A test of correspondence (fit) between a model and real data
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Mendel's Second Law
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Independent Assortment
-Genes encoding different characteristics segregate independently of each other when gametes are formed - Has exceptions |
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Exceptions to Mendel's Second Law
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Epistasis
Linkage Lethal genes |
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Altered locations of centromeres
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Metacentric (normal)
Submetacentric - off center Acrocentric - super close to the end Telocentric - at the end |
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Parts of cell cycle and what happens during each
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G1: cell grows
G0: (possibility) - non-dividing phase G1/S checkpoint: After this, the cell is committed to dividing S: DNA duplicates G2: cell prepares for mitosis G2/M checkpoint: Cell can divide Mitosis: Mitosis takes place Interphase: Cell growth M phase: nuclear and cell division Cytokinesis: cell divides and begins the cycle again. |
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Interphase
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The nuclear membrane is present and chromosomes are relaxed.
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Prophase
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Chromosomes condense. Each chromosomes possesses two chromatids. The mitotic spindle forms
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Prometaphase
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The nuclear membrane disintegrates. Spindle microtubules attach to chromatids
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Metaphase
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Chromosomes line up on the metaphase plate
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Anaphase
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Sister chromatids separate and move towards opposite poles
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Telophase
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Chromosomes arrive at spindle poles; nuclear membrane re-forms and the chromosomes relax
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Why is meiosis necessary?
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To reduce chromosome numbers. The fusion of 2N gametes would make 4N zygotes in generation 1. In the next generation, fusion of gametes would make 8N zygotes. This is not sustainable...
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What kind of division takes place in meiosis I and meiosis II?
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In meiosis I, reduction division takes place as cells go from 2n to n. In meiosis II, equational division takes place as the sister chromatids separate and cells are still "n."
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Subdivisions of prophase I
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Leptotene
Zygotene Pachytene Diplotene Diakinesis |
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Where does crossing over occur?
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In Prophase I: specifically, in the Zygotene, Pachytene, and Diplotene parts.
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What happens in the subdivisions of prophase I?
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Chromosomes pair -- synaptonemal complex -- chiasmata may occur
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What are chiasmata
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A chiasma is the point at which two homologous non-sister chromatids exchange genetic material.
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Where exactly are two alleles of a genotype, for example those of Rr?
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They are located on homologous chromosomes.
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Where (when) do homologous chromosomes replicate?
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During the S phase of meiosis
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How do you perform a branch diagram?
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Break up a multi-hybrid cross into monohybrid crosses. Determine the probability of each character. Combine individual characters and the associated probabilities by multiplication.
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When exactly does independent assortment occur?
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Occurs for genes that are on different chromosomes (or far apart on the same chromosome).
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So what happens when genes are close together on the same chromosome?
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The genes segregate together.
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Why was Mendel "lucky"?
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He did not observe linkage in his crosses. The genes for the characteristics he tested were all far enough away from each other.
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What was the contribution of Thomas Hunt Morgan to genetics?
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He related the chromosome to its role in heredity and studied the fruit fly Drosophila.
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What makes the fruit fly a good choice for studying?
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Small size, short generation time (10 days), easy to culture in laboratory, small genome, large chromosomes, many mutations available
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How many chromosomes do Drosophila have?
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3 pairs of autosomes and X and Y (2n = 8)
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How was it discovered that white eyes in Drosophila is an X-linked trait?
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A white male and a wild female were crossed, leading to all red-eyed males and females. Then the F1 was intercrossed, resulting in red-eyed males and females, and also white males!
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What are the clues that a gene is sex-linked?
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Results of reciprocal crosses (phenotypes of male and female switched) are not the same, different phenotypic ratios in the two sexes
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So how are there white-eyed females in Drosophila??
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White-eyed females have two X chromosomes and a Y. Xw, Xw, Y. Nondisjunction!
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What are the implications of nondisjunction occurring in meiosis?
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Nondisjunction is when meiosis "goes wrong" and both homologs end up in the same daughter cell. This can cause gametes that have two X chromosomes or both an X and a Y chromosome.
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Does nondisjunction happen in Meiosis I or Meiosis II?
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either
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How do you determine the sexual phenotype of a fly that has an unusual sex chromosome makeup?
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Look at the ratio of X chromosomes to autosomes. i.e. assume autosomes are AA.
Ratio <.5 -- metamale Ratio = .5 -- male Ratio > .5 -- intersex Ratio = 1 -- female Ratio > 1 -- metafemale |
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What are the sex chromosomes in birds?
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W and Z; WZ are females and ZZ are males.
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In peafowl, cameo (brown) is what kind of trait?
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Z-linked recessive, therefore it affects mostly females instead of males
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Where are the X and Y chromosomes homologous?
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At the pseudoautosomal regions which are essential for X-Y chromosome paring in meoisis in the male
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What are the implications of our sexually dimorphic sex chromosomes?
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Sex linked inheritance, dosage compensation, X-inactivation and mosaicism
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How did X-inactivation evolve?
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1) The Y-chromosome gradually lost genes during evolution
2) Males evolved mechanisms to coax more expression from the remaining X chromosome 3) Now for females, X expression exceeds that from autosomes 4) Females evolved mechanisms to silence many of the genes on the second X-chromosome 5) These mechanisms are called X-inactivation |
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What is a Barr body?
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A condensed (inactivated) X chromosome
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What is important about hypohydrotic ectodermal dysplasia?
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an X-linked recessive gene that causes the absence of sweat glands. Women are usually "mosaics"
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What is mosaicism in gene expression?
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Individuals will have parts of their body expressing the trait and other parts not expressing the trait, ex. patches of skin lacking sweat glands
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How are calico cats related to gene expression?
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Alleles determine if the fur will be orange or brown/black. X-inactivation in females produces patches of orange or black. White spots are due to another gene that controls spotting.
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What does Klinefelter syndrome mean?
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XXY, affects males, slightly feminized physique, breast development, little body hair
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What is haplodiploidy?
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A sex determination method in bees, wasps and ants that means sex is determined by the number of chromosome sets (males - n, females - 2n)
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How is sex determined in the honeybee?
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Polygenic - five genes are involved in the sex determining locus
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What determines sex in turtles and alligators?
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Temperature!!
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What complications are there with Mendel's laws?
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Multiple alleles
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What do multiple alleles do?
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Relative dominance - there is an order to the dominance.
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Incomplete dominance
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Phenotype of the heterozygote is the same as the phenotype of one of the homozygoes
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Codominance
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Phenotype of the heterozygote includes the phenotypes of both homozygotes
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What is penetrance?
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The % of individuals expressing a trait
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What does a sex-influenced trait do?
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The trait could be dominant/recessive differently in each sex!
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What do blood group alleles do?
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Alleles of the ABO locus enzymatically alter the carbohydrate antigen
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What is the enzymatic activity of the O allele in blood type?
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does not add an enzyme.
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What does the A allele do for enzymatic activity?
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adds galactosamine
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What does the B allele do for enzyme activity?
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adds glucosamine
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What genotypes are found for blood type?
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6: OO, AO, AA, BO, BB, AB.
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Describe bloodtype O: antigens, genotypes, and antibodies?
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no antigens, OO, anti-A and anti-B antibodies
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Describe bloodtype A: antigens, genotypes, and antibodies?
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antigen A, genotypes AA or AO, anti-B antibodies
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Describe bloodtype B: antigens, genotypes, and antibodies?
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antigen B, genotypes BB or BO, anti-A antibodies
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Describe bloodtype AB: antigens, genotypes, and antibodies?
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Antigens A and B, AB, no antibodies present
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What blood type is a universal recipient and why?
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Type AB are universal recipients because their blood contains no antibodies :)
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What blood type is a universal donor and why?
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Type O are universal donors because none of the blood types have O antibodies.
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What happens when an incompatible blood type donation is made?
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Blood cells that react with the recipient antibody clump together.
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What makes lethal genes difficult to observe?
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Offspring may die in utero! An allele can be dominant with respect to something physical but recessive with respect to lethality!
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What is epistasis?
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The interaction of alleles from different genes to determine phenotype
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What will happen if two mutations are on different genes?
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They will complement each other... crossing two whites would get a purple.
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What will happen if two mutations are at the same locus?
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They cannot complement each other.
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How to identify complementation groups
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perform true-breeding (homozygous) crosses and see if the mutations complement each other.
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What are the predicted phenotypic ratios of a heterozygous dihybrid cross according to Mendel's laws?
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9:3:3:1
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What are the predicted phenotypic ratios of a heterozygous cross for a gene that has an epistatic interaction?
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9:7 (also 9:3:3:1 but the 3,3, and 1 are all the same phenotype)
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Suppressing genes
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an example of epistasis.
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What is an example of recessive epistasis?
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Coat color in labrador retrievers
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What is an example of dominant epistasis?
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Color in squash
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What is an example of duplicate recessive epistasis?
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Albinism in snails
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How are identical/nonidentical twins identified in a pedigree?
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Identical have a line between the lines going to them, like an A. Nonidentical are denoted by one line splitting to two offspring.
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How are generations identified in a pedigree?
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A Roman numeral at the left.
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How are family members within each generation identified in a pedigree?
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Arabic numerals; left to right in birth order
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What are characteristics of the inheritance of autosomal recessive traits?
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Appear equally in males and females
Skip generations More likely to appear among progeny of related parents. |
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How are related parents identified on a pedigree?
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A double line between them
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What are characteristics of the inheritance of autosomal dominant traits?
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Appear equally in males and females
Unaffected persons do not transmit the trait Affected persons have at least one affected parent |
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X-linked recessive inheritance pattern
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An affected male does not pass the trait to his sons but can pass the allele to a daughter who is unaffected and passes it to sons who are. Grandfather-->(carrier daughter)-->grandson
Appear more frequently in males |
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X-linked dominant inheritance pattern
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Do not skip generations
Affected males pass the trait on to all their daughters and none of their sons Affected females (if heterozygous) pass the trait on to about half of their sons and about half of their daughters |
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Y-linked inheritance pattern
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Traits only appear in males
All male offspring of an affected male are affected |
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What does prenatal testing do?
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Detects major chromosome anomalies early
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What are some methods of prenatal testing?
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ultrasound
maternal blood tests amniocentesis chorionic villus sampling (CVS) |
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what is amniocentesis?
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A sterile needle is inserted into the amniotic sac and amniotic fluid is withdrawn. The fetal cells in the amniotic fluid are separated and cultured; then, chemical analysis, DNA analysis, and chromosomal analysis are performed on the cultured cells.
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What is chorionic villus sampling?
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A catheter is inserted, placed into contact with the chorion (the outer layer of the placenta); suction removes a small piece of the chorion and cells are used for many genetic tests; culturing is not required.
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What are some genetic diseases and disorders that can be detected prenatally?
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Chromosome abnormalities, cleft lip and palate, dwarfism, hemophilia, sickle-cell anemia, Tay-Sachs disease
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What is aneuploidy?
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An abnormal number of chromosomes; usually results in prenatal death. The frequency of chromosomal abnormalities increases with age.
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How does Downs Syndrome result?
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Trisomy 21
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What is the effect of extra Y's
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little effect
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What is the effect of extra X's
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mild X-inactivation
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What is the effect of Trisomy X?
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normal females
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What is the effect of double Y?
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normal males
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What is the effect of Klinefelter (XXY)?
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male intersex, retarded
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What is the effect of Turners syndrome (X)?
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female, not fertile
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What is phenylketonuria (PKU)?
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An autosomal recessive condition that is the deficiency for phenylalanine hydroxylase, which is the rate-limiting enzyme for breaking excess phenylalanine. This results in increased levels of phenylalanine in the body, harming the central nervous system and causing brain damage & retardation.
Treatment - diet really low in phenylalanine. |
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What is genetic counseling?
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Helping people understand and adapt to the implications of genetic contributions to disease
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How to calculate allele frequencies of a specific allele from genotype frequencies?
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1*(homozygous frequency)+1/2*(heterozygous frequency)
OR [1*(#homozygous)+(1/2*(#heterozygous)]/population |
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What are the Hardy-Weinberg expectations for allele frequencies?
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Random mating will produce genotypes of the next generation in proportions p^2(AA), 2pq(Aa), and q^2(aa).
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Frequencies of alleles in a situation with three alleles
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p^2, 2pq, q^2, 2pr, 2qr, r^2
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Allelic frequencies of X-linked alleles
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for females: normal;
for males: p and q (for X1Y, X2Y) |
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Testing for conformance to Hardy Weinberg expectations
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1) Find out what p and q are
2) Calculate expected genotypic frequencies based on p^2, q^2, and 2pq 3) Compare with Chi-square test |
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What are the four forces that cause deviations from H-W expectations in allele frequency?
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1) random genetic drift
2) mutation 3) migration 4) selection |
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What does NOT alter allele frequencies?
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Inbreeding
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What does inbreeding result in?
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A loss of heterozygosity (the heterozygous cross splits mostly between the AA and aa and to a further extent as time goes on)
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What is Ne?
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the genetically effective population size-- the population that can pass its genes on to the next generation. Ne is almost always smaller than the census size of the population
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What is mutation's effect on allele frequencies?
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Mutation changes allele frequencies very slowly. It is the ultimate source of evolutionary change but it is not a strong force changing allele frequency by itself.
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What is migration's effect on allele frequency?
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Migration only causes the population to deviate from H-W expectations when there is a very high level of migration.
delta q = m(q1-q2) i.e. if the difference in allele frequency is small (0.1) and the migrants are 1%, the change in allele frequency in one generation is 0.001 or 0.1%. The difference after a 1% migration is very insignificant. |
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Selection - when will delta q be the greatest?
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When q is at a high frequency - when there are a lot of recessive homozygotes (q^2) to be selected against.
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What is the long-term effect of mutation?
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Equilibrium is reached between the forward and the reverse mutations
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What is the long-term effect of migration?
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Equilibrium is reached when allelic frequencies of source and recipient population are equal
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What is the long-term effect of genetic drift?
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Fixation of one allele
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The larger the genome size the ______
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more deleterious (junk, repeated) DNA
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Within groups, variation in genome size is largely due to:
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the accumulation of repetitive DNA
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Denaturation/renaturation (hybridization)
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You can melt the two strands of DNA apart by heating them in solution, then when you cool the solution they will find their partners again!
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The rate of renaturation depends on:
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Concentration and complexity.
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What is a Cot curve and what does it show?
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A Cot curve plots concentration (mole * sec/L) against fraction reassociated.
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Describe the Cot curve of Mammalian DNA
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Complex - curved. It is a mixture of components renaturing at different rates.
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Prokaryotic chromosome packaging
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Rotating - under or over
Supercoiling - positive or negative Proteins anchor chromosomes to cell membrane |
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At the simplest level, chromatin is a...... how wide is it?
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double-stranded helical structure of DNA; 2 nm long.
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DNA is complexed with ______ to form nucleosomes.
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histones
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Each nucleosome consists of ___ histone proteins around which the DNA wraps ____ times.
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8, 1.65
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A ___________ consists of a nucleosome plus the H1 histone. How long is it?
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chromatosome; 11 nm.
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The nucleosomes fold up to produce a ___-nm fiber
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30
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The folded nucleosomes form loops averaging ____ in length
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300 nm
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The 300-nm fibers are compressed and folded to produce a ___-wide fiber
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250-300-nm
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Tight coilings of the 250-nm fiber produces the _____ of a chromosome, and the chromosome is ~ ___ wide.
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chromatid, 1400 nm
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What is the fundamental repeating unit of chromatin?
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The nucleosome
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What breaks up the "beads-on-a-string" of chromatin?
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nuclease
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What happens after nuclease breaks up the beads of chromatin?
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Individual beads attached to about 200 base pairs of DNA are floating around. Nuclease destroys all of the unprotected DNA floating off of it, and leaves a core of proteins attached to 145-147 base pairs of DNA -- 11 nm long spheres.
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How many histones are there on a nucleosome?
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8 in the core and H1 to lock the loops
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What are found on the ends of every chromosome?
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Telomeric repeats
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What measures does a cell take to ensure that chromosome ends are protected?
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Loose ends are degraded or attached to other pieces of DNA; special structures protect the ends from degradation
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What is an example of a structure that ties a degradation-resistant knot on the end of the chromosome?
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T-loop
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What are three major types of chromosome mutation?
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Chromosome duplication (2n = 6) -- extra genes
Aneuploidy (trisomy) (2n+1 = 7) -- extra chromosomes Polyploidy (Autotriploid) (3n = 9) -- extra sets |
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What happens in chromosome duplication?
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A segment of the chromosome is duplicated.
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What happens in chromosome deletion?
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A segment of the chromosome is deleted.
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What happens in chromosome inversion?
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A segment of the chromosome is turned 180 degrees.
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What happens in translocation?
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A segment of a chromosome moves from one chromosome to a nonhomologous chromosome or to another place on the same chromosome
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What are three developmental consequences of duplications/ deletions?
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Change in gene dosage
Over-or-under-expression of genes Imbalance in gene expression relative to other genes in the organism |
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What are three developmental consequences of inversions/translocations?
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Change in local gene environment
Differences in chromatin structure May alter gene expression Also -- developmental abnormalities |
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What are two structural consequences of inversions?
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Change in gene order disrupts pairing in meiosis
Leads to production of defective gametes (sterility) |
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What happens during alignment in prophase I of meiosis when there is a duplication or deletion in one of the chromosomes?
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A loop forms to accomodate the deletion or duplication while still aligning the homologous sequences.
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What is a paracentric inversion?
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An inversion which does NOT include the centromere
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What is a pericentric inversion?
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An inversion which includes the nucleus
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What happens during alignment in prophase I of meiosis when there is a paracentric inversion in one of the chromosomes?
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The chromosomes form an inversion loop, which allows the homologous sequences to align
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During prophase I for chromosomes where one has an inversion, what happens in the event of a crossover?
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One of the four chromatids now has two centromeres, and one lacks a centromere. Then in anaphase, the centromeres separate, and the dicentric chromatid breaks. The chromosome lacking a centromere is lost :'(
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What happens to the gametes of an inversion event that experienced crossover?
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Half are nonviable because they are missing some genes
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What is a pericentric inversion?
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An inversion which does include the centromere
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What happens during prophase I of meiosis when there is a pericentric inversion in one of the chromosomes?
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An inversion loop forms
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What happens if there is crossing over during the inversion loop event of prophase I involving a pericentric inversion?
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Two of the resulting chromatids have too many some genes and no copies of others. After anaphase II... recombinant gametes are nonviable because genes are either missing or present in too many copies
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What happens in a Robertsonian translocation?
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The short arm of one acrocentric chromosome is exchanged with the long arm of another, creating a large metacentric chromosome and a fragment that often fails to segregate and is lost.
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Name three consequences of translocations
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Change in local gene environment
Differences in chromatin structure May alter gene expression |
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What happens in a complex translocation heterozygote?
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A crosslike configuration forms in prophase I of meiosis, and in anaphase I they either separate in crosses or in vertical or horizontal T's. Either way, gametes resulting from adjacent I and adjacent 2 segregation are nonviable because some genes are present in two copies, whereas others are missing.
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Variation in the number of complete chromosome sets - what are three examples of polyploid plants?
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Banana - 3n
Strawberry - 8n Potato - 4n |
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Name a way autoploidy can occur
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non-disjunction (no cell division) in mitosis so the sister chromatids stay separate and the cell will have gone from 2n to 4n!
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What happens to triploid cells going through meiosis?
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They result in some gametes having extra chromosomes and some having none, so they're partially sterile.
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How can allo-ploidys be purposefully produced?
|
Hybridization - hybridization occurs between two diploid species (2n = 6) and this produces a hybrid with six nonhomologous chromosomes that do not pair and segregate properly...unbalanced/nonviable gametes; however, nondisjunction leads to a doubling of all chromosomes, producing an allotetraploid and chromosome pairing and segregation here are normal!
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What is the difference between autopolyploidy and allopolyploidy?
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Autopolyploidy is polyploids with multiple chromosome sets derived from a single species; alloploidy is polyploids with multiple chromosome sets derived from different species
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How does sheep cloning work?
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Mammary cells are cultured. A mammary cell with a nucleus is electro-fused with an ovum that the nucleus has been taken out of. The reconstructed cell is cultured inside a sheep. The embryo is recovered and implanted in a womb. Dolly is born!
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Fish cloning....
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hmmm
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Nullisomy
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loss of both members of a homologous pair
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Monosomy
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loss of one member of a homologous pair
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Trisomy
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Gain of one chromosome, resulting in three homologous chromosomes
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Tetrasomy
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Gain of two homologous chromosomes, resulting in four homologous chromosomes
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Describe the process of a Drosophila fly maturing from egg to adult.
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An egg develops into a hollow cylinder of cells.
Segmentation appears after a few hours. After 1 day, the larval stage begins..the embryo develops into a larva that passes through three stages. After 5 days the fly is now a pupa, which undergoes metamorphosis and an adult emerges after 9 days total. |
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What are the three sections of a fly?
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Head, thorax, abdomen
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Egg stage of a Drosophila egg:
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Diploid zygote --> multinucleate syncytium --> nuclei migrate to the edges and create the syncytial blastoderm --> cellular blastoderm after a cell membrane grows around each nucleus.
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In Drosophila: What are pole cells?
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Nuclei at one end of the blastoderm which become the primordial germ cells
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In a 2-hour Drosophila embryo, what occurs?
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The anterior-posterior and dorsal-ventral axes of the embryo are established.
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In a 10-hour Drosophila embryo, what occurs?
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The number and orientation of the body segments are established: head, thoracic segments, abdominal segments
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Where is embryonic patterning of adult structures stored in Drosophila?
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Imaginal discs of the larvae.
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What are three types of genes in the Drosophila formation?
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Egg-polarity genes
Segmentation genes Homeotic genes Gap genes |
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What is the function of the egg-polarity genes in Drosophila?
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Establishment of main body axes
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What is the function of the segmentation genes in Drosophila?
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Determination of number and polarity of body segments
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What is the function of the homeotic genes in Drosophila?
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Establishment of identity of each segment
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Dorsal-ventral axis formation in Drosophila: what does the dorsal gene do?
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Ovary - Affects expression of two other genes, twist and decapentaplegic
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Dorsal-ventral axis formation in Drosophila: what does the cactus gene do?
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Ovary - Traps Dorsal protein in cytoplasm
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Dorsal-ventral axis formation in Drosophila: what does the toll gene do?
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Ovary - alters dorsal protein, allowing it to dissociate from cactus protein and move into nuclei of ventral cells
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Dorsal-ventral axis formation in Drosophila: what does the twist gene do?
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Embryo - takes part in development of mesodermal tissues
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Dorsal-ventral axis formation in Drosophila: what does the decapentaplegic gene do?
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Takes part in development of gut structures
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Describe the dorsal-ventral axis formation--the role that the Dorsal protein plays
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After the nuclei migrate to the periphery of the embryo, the Dorsal protein becomes concentrated in the nuclei on the ventral surface
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Three key genes involved in the formation of the anterior-posterior axis
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bicoid
nanos hunchback |
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What does the bicoid gene do in Drosophila?
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Ovary - regulates expression of genes responsible for anterior structures; stimulates hunchback
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What does the nanos gene do in Drosophila?
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Ovary - regulates expression of genes responsible for posterior structures; inhibits translation of hunchback mRNA
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What does the hunchback gene do in Drosophila?
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Embryo - regulates transcription of genes responsible for anterior structures -- expressed from the anterior end to the middle.
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Three key genes involved in the segmentation of Drosophila?
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Gap genes
Pair-rule genes Segment-polarity genes |
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What do gap genes do in Drosophila?
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Delete adjacent segments
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What do pair-rule genes do in Drosophila?
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Delete same part of pattern in every other segment
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What do Segment-polarity genes do in Drosophila?
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Affect polarity of segment; part of segment is replaced by mirror image of part of another segment
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Even-skipped (eve) expression is stimulated and limited by expression of what genes? What is eve's expression as a result?
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Stimulated - bicoid and hunchback
Repressed - Giant and kruppel Eve is expressed in a narrow band, only one cell wide |
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What is a bithorax mutant of Drosophila?
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Has an extra pair of wings instead of halteres!!
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What can be said about the homeotic genes and their order?
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The arrangement of the genes on the chromosome corresponds to the sequence in which the genes are expressed along the anterior-posterior axis of the body!
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What do Hox genes do?
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They do in mammals what homeotic genes do in Drosophila. They control vertebrate segment identity, and are in the same order :).
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What are Hox proteins?
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Transcription factors that regulate gene expression in each segment
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What are the whorls 1-4 in a wild-type flower?
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Whorl 1: Sepals
Whorl 2: Petals Whorl 3: Stamens Whorl 4: Carpels |
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What do Class A genes affect?
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Whorl 1 and 2
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What do Class B genes effect?
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Whorl 2 and 3 - petals and stamen
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What do Class C genes effect?
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Whorl 3 and 4: stamen and carpel
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What demonstrated that somatic tissues have complete genetic material? (important exception??)
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Phloem tissue from the carrot is disrupted and single cells are isolated. A single cell is placed in a nutritive medium that contains growth hormones and eventually gives rise to a complete carrot plant!! (development of the immune system!)
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From where do lymphocytes originate?
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Stem cells in the bone marrow
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What happens when B cells encounter antigens?
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They mature into B plasma cells, which secrete antibodies that confer humoral immunity to the antigen
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What happens with T cells?
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They mature in the thymus and enter circulation. They attack by binding host cells and lysing them (cellular immunity)
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What happens in clonal selection of lymphocytes -- primary immune response?
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Each lymphocyte is specific for one antigen. When an antigen binds to a B cell, the B cell divides and clones itself. This is the primary immune response. Some cells differentiate into antibody-secreting plasma cells. Antibodies are specific to the antigen.
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What happens in secondary immune response?
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Memory cells remain in circulation and if a second exposure of the same antigen occurs, the antigen binds to the memory cells which rapidly give rise to a secondary immune response!! Yay :)
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Where do antigens bind on an immunoglobin molecule?
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Between the light chan and the heavy chain at the end, in the Variable region.
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How much possibility is there for variance with combinatorial diversity?
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A ton!! With V (variable) segments, J (junctional) segments, and D (diversity) segments, there are 10 million possible immunoglobulins!! We produce an extraordinary diversity of antibodies.
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What is a discontinuous characteristic?
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Exhibits only a few, easily distinguished phenotypes: plants are either one or the other!
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What is a continuous characteristic?
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Exhibits a continuous range of phenotypes
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What happens when more loci affect the trait?
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The number of phenotypic classes increases.
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Variance formula
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s^2=(1/(N-1))*sum of(x-mean x)^2
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What does a positive correlation between two traits indicate?
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A direct association between variables
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What is the regression coefficient?
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Represents the slope of the regression line; also equals h^2
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Response to selection
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R = h^2*S
where R = new generation average - total population average & S = selected parents' average - total population average |
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Is there a limit to selection?
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continued selection should eventually fix desirable alleles at every locus, so that no further evolution/improvement of traits is possible.
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Why do relatives look alike?
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Shared environments - prenatal and postnatal
Shared genetics - additive components; dominance components |
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Monozygotic twins
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Identical
Separate or single amnion; separate or single chorions and placentas |
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Dizygotic twins
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Share 50% of genetic material
Fraternal Separate amnions & chorions, fused or separate placenta |
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additive components
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probability of sharing a parental allele
dizygotic twins - 50% |
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dominance components
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probability of sharing the same genotype
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What effects can maternal environment have on babies?
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IQ -- birth weight
Twins are lighter at birth Dietary supplements Alcohol, drug, cigarettes Maternal lead exposure |
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What is the function of telomerase?
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replicates the ends (telomeres) of eukaryotic chromosomes. the RNA part of the enzyme has a template RNA PRIMER that is complementary to repeated sequences in the telomere and pairs with them, providing a template for the synthesis of additional copies of the repeats.
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