From the marriage of a man and a woman with normal vision, a color-blind boy and a girl with normal

From the marriage of a man and a woman with normal vision, a color-blind boy and a girl with normal vision were born. The girl grew up and married a man with normal vision. What is the likelihood of a boy with normal eyesight being born from this marriage?

X (D) – normal vision, X (d) – color blindness. If a sick son is born from a marriage of a man and a woman with normal vision, then the woman is heterozygous for this trait and is a carrier of the gene for color blindness.

Parents: X (D) X (d) × X (D) Y

Gametes: X (D) X (d) X (D) Y

Offspring: X (D) X (D) healthy daughter, X (D) Y healthy son, X (D) X (d) healthy daughter, carrier, X (d) Y son with color blindness.

If a daughter with normal vision is homozygous for this trait and is not a carrier of the color blindness gene, she married a healthy man, then the probability of having a healthy son is 1/2 (correct answer is 5).

Parents: X (D) X (D) × X (D) Y

Gametes: X (D) X (D) Y

Offspring: X (D) X (D) healthy daughter, X (D) Y healthy son.