In humans, color blindness is caused by a recessive X-linked gene. The husband and wife have normal vision

In humans, color blindness is caused by a recessive X-linked gene. The husband and wife have normal vision, despite the fact that their fathers are color blind. What is the likelihood of having children with color blindness in this family?

Let’s designate the chromosome containing the gene that causes the development of color blindness as Xd. Then the chromosome that determines the development of the normal ability to differentiate colors will be XD.

The male and female fathers will be XdY, they will produce Xd and Y sperm.

His man gets Y from his father, which determines his gender. Therefore, if he is free from color blindness, his genotype looks like this – XDY, and the sperm produced by him – XD and Y.

To a healthy woman, her father transmits a pathological gene, thereby she becomes its carrier – XDXd, her body produces eggs XD and Xd.

Possible options for the offspring of this married couple:

healthy girls (XDXd, XDXd) – 50%;

healthy boys (XDY) – 25%;

boys – color blind XdY – 25%.

Answer: the probability of having children – color blind in this family is 25%.