Color blindness in humans is controlled by a gene located on the X chromosome (sex-linked). The normal gene, Xc, needs only to be present as a single copy for an individual to have normal vision. Since males and females have different numbers of X chromosomes, the incidence of color blindness varies between sexes.
If a color blind man marries a woman with normal vision whose father was color blind, what proportion of their sons and daughters would you expect to be color blind? Use Xc for the normal gene, Xc for the mutant gene, and Y for male chromosomes.