Cystic fibrosis (CF) is an autosomal recessive disorder. A healthy man whose sister has CF, marries a healthy woman whose brother has CF.

Cystic fibrosis (CF) is an autosomal recessive disorder. A healthy man whose sister has CF, marries a healthy woman whose brother has CF. What is the probability that this couple could have a child with CF? (Hint: conditional probability) Show your work.