Question

Chloe’s mother wants to have another child. However, she is concerned that a second child might also have CF, so she encourages Chloe’s stepfather to be tested. Tests reveal that he does NOT carry the CF gene. What is the chance that a second child born to Chloe’s mother and stepfather will have CF?

Answer 1

CF is a recessive type of disorder which means that both parents must carry the gene in order for the child to inherit the disease. If the child only inherits 1 copy of the affected gene, then the child becomes a carrier. Carriers do not manifests symptoms of the disease but they can pass the disease to their children.
With both parents as carriers, they will have the following chances: 50% carrier children, 25% affected child, and 25% normal child.