Color blindness is a ..... trait.

Testing for $\beta$-thalassemia should be done before marriage.

If a man who is colour blind marries a woman who is pure normal for colour vision,the chances of their sons having colour blindness is

$A$ color-blind man marries a woman with normal vision,whose family has no history of color blindness. What is the probability that their daughter's children (grandsons and granddaughters) will be color-blind?

$A$ color-blind girl is rarely born. This occurs only when:

Sex-linked disorders are mostly . . . . . . .