Question

The gene for brown eyes (B) is dominant over the gene for blue eyes (b). Two brown-eyed people have a blue-eyed child. Which genotypes make this possible?
Question 13 options:

The mother and father are both homozygous brown-eyed (BB).

The mother is homozygous brown-eyed (BB) and the father is heterozygous brown-eyed (Bb).

The mother is heterozygous brown-eyed (Bb) and the father is homozygous brown-eyed (BB).

The mother and the father are both heterozygous brown-eyed (Bb).

Answer 1

Answer: The mother and the father are both heterozygous brown-eyed (Bb).

Explanation: Both parents are brown eyed because they both have a heterozygous allele (Bb) for brown eye. The heterozygous allele has one gene for brown eye (B) which is dominant over the recessive gene for blue eye (b). So when the two heterozygous brown eye individuals cross, there is a chance of having a blue eyed child (bb).

See the attached punnet square for more illustration.