From the intro story of chapter 1 and its associated exercis

From the intro story of chapter 1 and its associated exercises, you already knew that albino is a rare recessive genetic disease. Sally and her parents are normal but her sister is albino. It seems that Sally has chance to carry the albino allele. What is the chance? If she marries a normal looking boy Tom. in whose family the only albino person is Tom\'s brother, what is the chance for Sally and Tom to have an albino baby? (Note there are 2 small question)

Solution

The chance that Sally can carry the albino allele will be 1/4.

The chance for Sally and Tom to have an albino baby will be 2/3*2/3*1/4 .

Explanation:Since albino is a recessive genetic disease. parents who are normal can be carriers of the disease.Mother and father can be heterozygous Aa.So each will contribute 1/2 to Sally.So, that will be 1/2 *1/2 = 1/4 = 25% chance.Similarly , The chance for Sally and Tom to have an albino baby will be 2/3*2/3*1/4 .