Question

3) In mice, brown eyes (B) are dominant over blue (b). A homozygous brown-eyed male mouse mates with a blue-eyed female and they have offspring. What are the phenotypes and genotypes of their offspring? What are the genotypes of the parents?

Answer 1

(B) are dominant over blue

3) In mice, brown eyes

Answer 2

The babies will all have brown eyes because a homozygous dominant vs. homozygous recessive will always result in the dominant trait showing. The parents genotypes have to be BB for the male and bb for the female because homozygous means the letters will match for genotype so male has to have BB, and the female shows the recessive trait so she has to have bb. The only genotype the babies can have is Bb because the parents each only have a B and a b to give respectively so that's all they can do. This means the babies will have the brown eyed trait and a heterozygous genotype.