The color blindness gene is recessive and X linked. It is written as Xb. A woman who is color blind has a son with a man with normal vision. What is the genotype of the son? Use a Punnett square to answer the question.

Genotype of the son = XᵇY.

Explanation:

The trait is X linked recessive that means in female if both the alleles are Xᵇ then only female will show traits of color blindness whereas in males since they only have one X chromosome even if one Xᵇ will be present, he will show color blindness traits. But in the given example, woman is color blind while man has normal vision. It simply means that genotype of woman is XᵇXᵇ while that of man is XY.

The Punnett square diagram depicting the cross is attached as under:

It may be noted that their son will be born with a genotype XᵇY so as already explained he will be color blind.