L41 BIOL 2970 Lecture 23: Bio 11-18

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tealwasp384

6 Feb 2019

School

WUSTL

Department

Biology And Biomedical Sciences

Course

L41 BIOL 2970

Professor

Chalker

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Document Summary

In a one locus model any nonadditive variance is called dominance variance. If we were measuring 2+ loci the possible interaction between epistatic loci among different loci could lead to an additional category of nonadditive variance: dominance and epistatic variance population level. Mendelian dominance is necessary but not sufficient for dominance variance at the. If dominant allele is common, mating random: copies occur in homozygous and heterozygous genotypes, copies in heterozygotes contribute twice as much to populational variation as do copies in homozygotes, produces some non-additive genetic variance. Under strictly additive gene action (heterozygous phenotype is exactly intermediate. Problem: there are other loci that are involved that we haven"t measured between alternative homozygotes), all genetic variance is additive genetic variance. Correlations between parents and offspring is the way of measuring genetic contribution, in this way heritability is just a fancy way of saying correlation. In the past one had to estimate heritability without measuring genotypes.

Related Questions

GENETICS : You perform a dihybrid cross between two dogs that are each BbFf. Where not specified otherwise, assume black fur B is completely dominant to white fur b and furry F is completely dominant to hairless f

1. What genotypes at one locus will be epistatic to what genotypes at the other locus, if hair color and hair presence were the only measured phenotypes? (you may find it helpful to write out the genotypes and the phenotypes each would produce, and remember that epistasis is involved in this question).

What phenotypic ratios would you expect in the following scenarios (assume, unless otherwise noted, that the epistasis in part 1 still applies)?

2. Black B is completely dominant to albino b, furry F is completely dominant to hairless f

3. Black displays incomplete dominance to albino , and furry is codominant with hairless

4. Animals that are heterozygous at either locus are black and furry, overriding the other locus' geneotype

5. The black allele B displays epistasis when present at even one copy that masks the effects of the hairless f allele

6. It takes two black B alleles to mask the effects of the hairless f allele

7. Both the black alleles B and furry alleles F are lethal in their homozygous dominant states

8. Both the albino alleles b and hairless alleles f are lethal in their homozygous recessive states

9. Female dogs die when they have homozygous recessive or homozygous dominant states for either locus (dogs use XY inheritance for sex like we do). Note sex of doss in your phenotype ratios.

10. The black allele B although completely dominant, is the only 70% penetrant in heterozygotes and is 90% penetrant in homozygotes for the B allele

11. The hairless allele f is dominant in males and recessive in females

QUESTION 1

Jim is blood type A, his brother John is type O and his sister Jane is type AB. What are the genotypes of their parents?

Which of the following is true for alleles that show incomplete dominance?

Heterozygotes have a genotype like the dominant allele.

Homozygotes have a genotype like the recessive allele.

Heterozygotes have a phenotype intermediate between the dominant and recessive alleles.

Homozygotes have the same phenotype as the heterozygotes.

QUESTION 3

Which principle of inheritance concluded that when games are formed in meiosis, the two alleles of each gene separate from one another, and each gamete receives only one allele?

independent assortment

Which term best describes a condition in which alleles at one locus can alter the expression of alleles at another locus?

polygenic inheritance

A single unit of genetic information located on a chromosome defines:

The physical expression (appearance or function) of an organism's genes defines:

genotype

a single characteristic

Palomino horses (golden color with a blond mane) are an incompletely dominant trait produced by the combination of the chestnut color allele and the cream color allele. If you wanted to produce as many palominos as possible, which mating strategy below would be the best choice?

Which term best describes the effect of a single gene on multiple aspects of the phenotype?

polygenic inheritance

QUESTION 9

Which term best describes the separate expression of both alleles for a single trait in the same cell?

polygenic inheritance

QUESTION 10

One form of a gene found on a single chromosome defines:

A chocolate lab (whose mother was a yellow lab) is mated with a black lab whose genotype is BbEe. What fraction of the offspring would be expected to be yellow labs?

What type of allele is always expressed regardless of whether the individual is homozygous or heterozygous for it?

Both the dominant and recessive alleles

Given the parents AABBGgHhrr Ã AabbGgHhRr, assume simple dominance and independent assortment. What proportion of the progeny will be expected to have the genotype AaBbggHHrr?

___________________ is defined as having two of the same type of allele for a particular trait.

The physical position of an allele on a single chromosome defines:

Which term best describes two or more genes affecting the phenotype in an additive fashion?

codominance

polygenic inheritance

Short answers please

1. What is the ultimate effect in an XY human with its SRY genemutated?

2. In humans, the allele for brown eye (B) is dominant to blue(b) eye color. If two heterozygous parents produce children, whatis the probability that:

a. The first child has brown eyes, and the next two childrenhave blue eyes?

b. If the couple above eventually produces a total of sixchildren, what is the probability that three of them will be boyswith brown eyes, and three of them girls with blue eyes?

3. In a paternity dispute, a type AB woman claimed that one ofthe four men was the father of her type A child. Which of thefollowing men could be the father of the child on the basis of theevidence below? Give your reasoning.

Man #1 = type A

Man #2 = type B

Man #3 = type O

Man #4 = type AB

4. Several mating were made among all-white cats. The progentfrom these mating showed the following phenotypic frequency:

All-white cats = 12/16

Black cats = 3/16

Gray cats = 1/16

a. Diagram the cross showing the genotypes of the parents, andtheir progeny as given above,

b. Which gene is epistatic? Explain your answer.

5. Mitosis and meiosis differ in that

a. homologues are seperated in prophase of mitosis

b. homologues are seperated in prophase I of meiosis

c. homologues are seperated in prophase II of meiosis

d. sister chromatids are seperated in prophase I of meiosis

6. The phases of meiosis that most resemble those of mitosisare

a. the meiosis I phase

b. the meiosis II phase

c. meiosis I, except for the pairing of homologues

d. meiosis II, except for the pairing of homologues

7. Genetic variability in sexually reproducing organism s arisesfrom

a. crossing over events between sister chromatids

b. crossing over events between nonsister chromatids

c. egg and sperm genetic recombination from distinctindividuals

d. egg and sperm recombination from an individual

8. A female contains an extra X chromosome, resulting fromnondisjunction. When this gamete is fertilized with normal sperm,it would result in an individual of a genotype

a. XXX

b. XXY

c. XYY

d. all of the above

e. only a and b

9. A diploid organism has the genotype AaBbCcDdEe. How manydifferent types of gametes can this individual produce?

a. 5

b. 10

c. 25

d. 32

e. 625

10. Assuming complete dominance, what is the phenotype ratio ofthe offspring of the cross AaBb x aabb?

a. 1:1

b. 3:1

c. 1:2:1

d. 1:1:1:1

e. 9:3:3:1

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L41 BIOL 2970 Lecture 23: Bio 11-18

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