It is well known that the gene that causes the development of color blindness is inherited in the structure of the X chromosome. Let’s designate the chromosome with the gene that causes the development of this pathology as X d. A chromosome with a gene that causes a person to develop a normal ability to distinguish colors is denoted as X D.
The father of a woman with color blindness had the X d Y genotype, he produced two types of spermatozoa – Xd and Y and was able to pass on to his daughter only the gene for color discrimination pathology in the X chromosome.
Since a woman, according to the condition of the problem, has normal vision, she is a carrier of the gene for color blindness. She has a heterozygous genotype X D Xd, produces eggs X D and Xd. It transfers both the pathological gene and the gene for normal vision to children.
A man, being color blind, has the X d Y genotype and produces sperm cells X d and Y.
The offspring of this married couple will be represented by the following possible options:
girls with normal vision, but who are carriers of the pathological gene (X D Xd) – 25%;
girls with color blindness (X d X d) – 25%;
boys with normal vision (X D Y) – 25%;
boys with color blindness (X d Y) – 25%.
Answer: the probability of having healthy children in the presented married couple is 50%.