Question

A dog breeder liked yellow and brown labrador retrievers. In an attempt to produce yellow and brown puppies, he bought a yellow Lab male and a brown Lab female and mated them. All the puppies produced in this cross were black

a. explain the result

b. how might the breeder go about producing yellow and brown Labs?

Answer 1

All puppies from a yellow Lab male and a brown Lab female being black is due to epistasis. The yellow Lab likely has the EeBb genotype and the brown Lab has the Eebb genotype, which results in black offspring due to the dominant B allele in the presence of an E allele.

Step-by-step explanation:

The result that all the puppies from the cross between a yellow Lab male and a brown Lab female are black can be explained by the genetic principle called epistasis. In Labrador retrievers, fur color is determined by two sets of alleles: one set for the E or e genotype and another set for the B or b genotype. A dog with the ee genotype will be yellow, regardless of the B/b alleles because the e allele shows epistasis and masks the expression of the B/b alleles. In the provided scenario, the black puppies' phenotypes suggest that the yellow Lab is likely EeBb and the brown Lab is Eebb. Since both dogs contribute an E allele, the epistatic effect does not come into play, resulting in black labs due to the dominant B allele.