Why do 25 percent of cf carrier s children get cystic fibrosis?

Cystic fibrosis (CF) is an autosomal recessive genetic disorder, meaning that a child must inherit two copies of the defective CFTR gene—one from each parent—to develop the disease. When both parents are carriers of the CF gene mutation, there is a 25 percent chance with each pregnancy that their child will inherit both defective genes, resulting in cystic fibrosis. Additionally, there is a 50 percent chance the child will be a carrier (inheriting one defective gene) and a 25 percent chance the child will inherit two normal genes.