A couple learns from studying their family histories that, in both of their families, they each have one unaffected grandparent that had siblings with cystic fibrosis-a rare autosomal recessive disease.
a) If the couple has a child, what is the probability that the child will have cystic fibrosis? probability = ___
b) If they have four children, what is the chance that the children will have the precise Mendelian ratio of 3:1 for normal:cystic fibrosis? probability = ___
c) If their first child has cystic fibrosis, what is the probability that their next three children will be normal? probability = ___