A couple has two children one normal and one with CF What is

A couple has two children, one normal and one with CF. What is the probability that the normal child is a carrier?

a. 2/3

b. 1/2

c. 1/4

d. 3/4

2. A phenotypically normal individual with a sibling that has cystic fibrosis marries a known carrier of the CF mutation. If they have a child, what is the probability that their child will develop cystic fibrosis?

a. 1/3

b. 1/8

c. 1/4

d. 1/6

Solution

1. A couple has two children, one normal and one with CF. The probability that the normal child is a carrier is 2/3

2. A phenotypically normal individual with a sibling that has cystic fibrosis marries a known carrier of the CF mutation. If they have a child, the probability that their child will develop cystic fibrosis is 1/6.