This is a genetic question: 4. John and Mary each have sisters with cystic fibrosis. They would like to marry and have children, but are concerned that they too may have a child with cystic fibrosis. Cystic fibrosis is an autosomal recessive disease located on chromosome 7. If John and Mary are each heterozygous for cystic fibrosis what is the probability of: A. Having a child with cystic fibrosis? B. Having two children that are affected? C. Having 4 children with normal phenotypes?.