A man with blue eyes married a woman with brown eyes, they had a blue-eyed son.

A man with blue eyes married a woman with brown eyes, they had a blue-eyed son. determine the genotype of the mother.

Answer: mother’s genotype Aa.

The father of this child is homozygous (aa), because blue-eyed is a recessive sign and there is no other option. But a mother with brown eyes can be either homozygous for this trait or heterozygous. In the first case, the child would be 100% brown-eyed, but in the second, 50% brown-eyed, and 50% blue-eyed.