A blue-eyed man married a woman with brown eyes, whose father has brown eyes and the mother is blue.

A blue-eyed man married a woman with brown eyes, whose father has brown eyes and the mother is blue. It is known that the conditional gene for brown eyes is dominated by blue eyes, what is the likelihood of having a baby with brown eyes.

Let’s designate the gene that causes the development of blue eyes in humans as m, then the gene for brown eyes will be M.

The mother of the brown-eyed woman had blue eyes. Consequently, she had a genotype mm homozygous for the recessive gene, produced the same type of eggs m, and could only pass on the gene for blue eyes to her daughter.

Thus, the brown-eyed woman is heterozygous – Mm. It is capable of producing two types of oocytes – M and m.

A blue-eyed man, like the mother of a woman with whom he marries, has a genotype mm homozygous for the gene for a recessive trait. It produces the same type of spermatozoa m.

The offspring of the described man and woman are represented by the following two possible options:

children homozygous for the recessive gene with blue eyes (mm) – 50%;

heterozygous children with brown eyes (Mm) – 50%.

Answer: the probability of having a child with brown eyes in this married couple is 50%.