A man who is color blind marries a woman who carries the gene for color blindness.

A man who is color blind marries a woman who carries the gene for color blindness. Can a healthy son be expected in this marriage? Can a color blind daughter be born in this family?

Color blindness is inherited as a recessive trait, it is localized on the X chromosome.

XD – normal color vision, Xd – color blindness.

First, let’s write down the genotypes of the parents:

father – ХdY, mother – ХDХd.

Crossing scheme:

Parents: XDXd x XdY,

Gametes: XD, Xdх Xd, Y

Children: XDXd (carrier girl), XDY (healthy boy), XdXd (color blind girl), XdY (color blind boy).

The probability that the son will be healthy is 1/4 or 25%, a color blind girl will be born – 25%. However, girls who are homozygous for this trait are not viable and often die in the womb.