(Solved): A married couple went to see a genetic counselor because each had a sibling with cystic fibrosis. ...

A married couple went to see a genetic counselor because each had a sibling with cystic fibrosis. The heritable form of cystic fibrosis is caused by a recessive allele of the CFTR gene. For our purposes we'll designate the wild-type allele CFTR, and the mutant allele that causes the disease cftr. Neither of the parents or any of the four grandparents are affected. However, each of the parents has a sibling that has cystic fibrosis. What are the chances that their child will be affected with cystic fibrosis? 1 A? B I Ff? T?