Question

Cystic fibrosis (CF) is a genetic disorder that affects mostly the lungs, but also the pancreas, liver, kidneys, and intestine. CF is inherited in an autosomal recessive manner with simple Mendelian inheritance. It is caused by the presence of mutations in the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein.

A normal couple intends to have children but consult a genetic counselor because the man has a sister with CF and the woman has a brother with CF. There are no other known cases in their family. They want to know:

(1) What is the probability that their first child would be normal? (2) What is the probability that their first two children would have CF? (3) If they would like to have five children, what is the probability

that at least two of them would be normal?

Answer 1

So final answers are as follows

1.75%

2.25%

3.75%