b. What colors and in what proportions would you expect among the puppies produc

Question

b. What colors and in what proportions would you expect among the puppies produced by a mating between a male from a pure-breeding black strain and a female from a pure-breeding yellow/pale skinned strain of Labradors?

c. With regard to fur color only, what colors and in what proportions would you expect among the puppies produced by a mating between a black male and black female (siblings) from the litter that was produced by the original cross above?

d. Is the relationship between the B and E loci with regard to fur and skin color an example of pleiotropy, epistasis, pleiotropy and epistasis, or neither epistasis nor pleiotropy? Defend (explain) your answer.

Labrador retrievers come in three basic colors, black, chocolate, and yellow. These colors are controlled by two unlinked genetic loci, B and E. Each locus has two alleles: B and b at the B locus; E and e at the E locus. Dogs with at least one B allele and one E allele have black skin and black fur. Dogs with at least one E allele but no B allele (i.e. are bb) have brown (chocolate) skin and brown fur. Dogs with at least one B allele but lacking an E allele (i.e, are ee) have black skin yellow fur. Dogs lacking a B allele and lacking an E allele have pale (yellow to light brown) skin and yellow fur.

Explanation / Answer

BEx be

F1 progeny: Bb, Be, bE, eE

3:1, 3 progeny with black skin and black fur and 1 progeny brown chocolate skin and brown fu

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