Question

In dogs, black fur (B) is dominant over yellow fur (b). A homozygous black dog is

mated with a yellow dog.

Do a punnett square to show the cross and predict the offspring (phenotypes and

genotypes).​

Answer 1

Answer:

B. b

B. BB. Bb

b Bb. bb

Phenotype - 1:2:1

Genotype - 3:1

Answer 2

The Punnett square to show the cross is done below and the offspring (phenotypes and genotypes) are predicted as well:

It is given that

Black fur is dominant - B

Yellow fur is recessive - b

Homozygous black dog is mated with a yellow dog.

Solution:

Since black dog shows dominant allele and it is homozygous, its genotype will be BB.

Yellow trait is a recessive trait, hence it will only be exhibited if present in homozygous condition. Thus its genotype will be bb.

Punnett square for the cross between $BB\times bb$ is shown below.

    B      B

b   Bb   Bb

b   Bb   Bb

All the offspring produced will be heterozygous. The genotype of all the offspring produced will be Bb. While the phenotype will be - all will exhibit black fur.