Question

Cross two heterozygous black mice and tell the possible phenotypes and

genotypes in their offspring.

Answer 1

Phenotype: 3 black mice: 1 brown mice

Genotype: 1 BB: 2Bb: 1bb

Step-by-step explanation:

This question involves a single gene coding for fur color in mice. The allele for black color (B) is dominant over the allele for brown mice (b). This means that a mouse that is heterozygous will be black.

If two heterozygous black parents are crossed i.e Bb × Bb, the gametes produced by each parent are: B and b. Using these gametes in a punnet square (see attached image), the following offsprings will be produced:

BB, Bb, Bb, and bb

- The phenotypes of this cross is 3 black mice: 1 brown mice

- The genotypes of the cross is 1 BB: 2Bb: 1bb