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8. Epistasis: Scientists have determined hair color and hair production are each due to a single gene. The genes are on different chromosomes. A dominant allele B causes production of brown color hair. bb individuals have blond hair. A dominant allele H is also required for hair generation. hh individuals are bald. Answer the following questions about his situation:

A. What is an epistatic gene?

B. What is the phenotype of a BbHh individual?

C. What will be the expected phenotypic ratios of the offspring from a BbHh X BbHh (double heterozygous) cross? Be sure to list the phenotypes and their ratios.

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Nestor Rutherford
Nestor RutherfordLv2
28 Sep 2019

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2. Labrador retrievers have 2unlinked genes that affect coat color. The %u201Ccolor%u201DB

gene: B is the dominantallele for black hair and b is the recessive allele for brown hair.The %u201Ccolor modifier%u201D E gene: E is the dominant allelethat does not affect hair color expression at the %u201Ccolor%u201Dgene, and e is the recessive allele which changes the hair color toyellow regardless of the genotype at the %u201Ccolor%u201D gene. Ifthe following two individuals were to mate, what would be thepossible PHENOTYPES (hair color) of their offspring and what wouldbe the expected ratio of those phenotypes in theiroffspring?

-- Male: heterozygous for the hair color gene, homozygous for thee allele. -- Female: heterozygous at both genes Please showwork

Labrador retriever dogs have two genes that affect coat color. One gene, the B locus, codes for the intensity
of eumelanin production in the dog’s coat. It has two alleles that produce either a black pigment (B) or a
brown pigment (b). Another gene, the E gene, is epistatic to the B gene. The dominant E allele causes
eumelanin to be deposited along the length of the dog’s hair shafts. The recessive e allele blocks the
deposition of eumelanin in the hair, so only the yellow producing phaeomelanin pigment is deposited,
resulting in yellow dogs. If you cross parents with the following genotypes, Bbee x bbEe, what phenotypic
ratio do you expect in their offspring?

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

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