A girl suffering from color blindness marries a healthy man.

A girl suffering from color blindness marries a healthy man. Determine the likelihood of having healthy children and suffering from color blindness?

As you know, the gene that causes color blindness is passed on to descendants as part of the X chromosome. Let’s designate the chromosome with the color blindness gene as Xd. A chromosome that contains a gene for normal color discrimination will be designated XD.

A girl with color blindness will have the homozygous genotype Xd Xd. This is a prerequisite for the phenotypic realization of pathology. It will produce the same type of eggs Xd.

A healthy man will have the XD Y genotype and will produce two types of sperm – XD and Y.

The offspring of this married couple will be represented by the following options:

girls carrying the gene for color blindness with normal vision (XD Xd) – 50%;

boys with color blindness (Xd Y) – 50%.

Answer: all boys born in this family will have color blindness; the probability of having a child with color blindness is 50%.