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

Answer:

There is no chance that a child of one parent who carries CF gene is born having Cystic Fibrosis if the other parent does not carry the CF gene.

Explanation:

Second child born to Chloe’s mother and stepfather will have Cystic Fibrosis only if they inherit one CF gene from each parent. Since stepfather is not carrier of CF gene, development of the disease at child is not possible.

A person who has inherited one CF gene from his/her parent will be a CF gene carrier, but will never develop Cystic Fibrosis. However as he/she a carrier of the CF gene, they can pass it on to their own child.