Mr Smith has a rare genetic disease His son and brother are

Mr Smith has a rare genetic disease. His son and brother are also affected, although two daughters and his wife are not Mr and Mrs Smith are considering having another child. What is the risk that their next child wll be affected? Select one: 0% 25% 100% 50% 67% A man and women decide to have 3 children. What is the likelihood that of their three children, two are boys? Select one: 1/4 3/8 1/8 1/2 3/4 Given the pedigree what is the most likely inheritance pattern of this trait?

Solution

In the 1st question, the males are affected means this is a Y-linked genetic disorder. So next child may be girl or boy. So the risk of affected child will be 50%.

In the 2nd question, out of 3 children, 2 will be boys probability will be 3/8.

solution

P(all female)= 1/2 x 1/2 x 1/2 = 1/8

P(all male ) = 1/2 x 1/2 x 1/2 = 1/8

P (1 girl, 2 boys)= 1/8 + 1/8 + 1/8 = 3/8