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

probability for Sally to be heterozygous carrier = 1/2.

probability of their baby to be albino = 1/2 multiplied by 1/4 = 1/8

Since Tom\'s genotype is not given in the question, there is a chance of \'AA\' as well as \'A*A\'.

If it is \'AA\' then there would be possiblity of having an albino baby. there is a possibility only if Tom is \'A*A\'

probability of Tom to be \'A*A\' is 1/2.

probability of an albino from two heterozygous parents = 1/4

therefore, taking into consideration the above two probabilities, it would be 1/8.