In Labradors, two genes interact to determine coat color. BB homozygotes and Bb heterozygotes are black, while bb homozygotes are brown. The second gene, E, is epistatic over the B gene, and ee homozygotes always have yellow fur. If you crossed a brown Labrador (bb Ee genotype) with a yellow Labrador (Bb ee genotype), what would be the expected phenotypic ratios of their progeny? Assume that the two genes are unlinked.

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Jamar FerryLv2

23 May 2019

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If you crossed two black labradors EeBb x EeBb, what ratios of coat color would you expect according to epistasis and the genetics of coat coloration in labradors?

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Labrador retriever dogs have two genes that affect coat color. One gene, the B locus, codes for the intensity
of eumelanin production in the dogâs 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 dogâs 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?