Question

A black lab is crossed with a yellow lab, and 1/2 of the offspring are black

and 1/2 are brown.
What are the genotypes of these two dogs?

Answer 1

Step-by-step explanation:

Assuming that black is the dominant trait and brown is the recessive trait, we can use the following notation to represent the genotypes:

B: black allele

b: brown allele

If the black lab is crossed with a yellow lab, which we assume to be homozygous recessive (bb), the possible gametes for each parent are:

Black lab (Bb): B and b

Yellow lab (bb): b and b

The Punnett square for this cross would look like:

Black lab (Bb): one dominant black allele and one recessive brown allele

Yellow lab (bb): two recessive brown alleles