1. How many are likely to be normal? 2. How many are like to be colour blind?

Question

A colour- blind woman marries a man with normal vission. They have ten children, six boys and four girls. Remember colour blindness is sex-linked.

Answer 1

The male offspring will all be colourblind, as they have the single X from the mother, which must carry the colour blind allele, and the Y from the father, which carries neither allele for colour blindness.

All females will be carriers, as they will have one X chromosome with the colourblindness, and one X with the dominant normal vision.

Answer 2

All 6 boys are likely to be color blind. The girls are normal or carriers.