The daughter of a color blind person who has normal vision marries a man with normal vision.

The daughter of a color blind person who has normal vision marries a man with normal vision. What will be the vision of their children if color blindness is due to a recessive gene linked to the X chromosome?

As you know, color blindness is inherited with a gene linked to the X chromosome.

Let’s designate the chromosome with the color blindness gene as Xd. Then the chromosome, which includes the gene that causes normal color vision, will be designated XD.

The woman’s father had color blindness, therefore, had the Xd Y genotype. He produced spermatozoa Xd and Y. He passed on a chromosome with a pathological gene – Xd to his daughter.

According to the condition of the problem, the woman has normal vision, therefore, she is a heterozygote – XD Xd. Such a woman produces eggs XD and Xd.

The man she fights with is healthy. He has the genotype

XD Y and produces XD and Y sperm.

From the marriage of the described man and woman, offspring are expected, represented by the following options:

girls with normal vision who are carriers of the pathological gene (XD Xd) – 25%;

girls with normal vision who are not carriers of the gene for color blindness (XD XD) – 25%;

boys with normal vision (XD Y) – 25%;

boys with color blindness (Xd Y) – 25%.