Labrador retrievers come in three basic colors, black, chocolate, and yellow. Th

Q: Labrador retrievers come in three basic colors, black, chocolate, and yellow. Th

Dog Color Genotypes Black BBEE, BBEe, BbEE, BbEe, BBEe, BbEe, BbEE, BbEe, BbEe Chocolate bbEE, bbEe, bbEe Yellow/black skin BBee, Bbee, Bbee Yellow/pale skin bbee Dog Color Genotypes Black BBEE, BBEe, BbEE, BbEe, BBEe, BbEe, BbEE, BbEe, BbEe Chocolate bbEE, bbEe, bbEe Yellow/black skin BBee, Bbee, Bbee Yellow/pale skin bbee

ID: 55162 • Letter: L

Question

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.

a. List all possible two-locus genotypes for each dog color below.

Black

Chocolate

Yellow/black skin

Yellow/pale skin

Explanation / Answer

Dog Color

Genotypes

Black

BBEE, BBEe, BbEE, BbEe, BBEe, BbEe, BbEE, BbEe, BbEe

Chocolate

bbEE, bbEe, bbEe

Yellow/black skin

BBee, Bbee, Bbee

Yellow/pale skin

bbee