2.16—Cystic fibrosis gene mutation effects

Cystic fibrosis is caused by recessive CFTR alleles that produce faulty chloride ion channels. Reduced chloride transport changes water movement by osmosis, making mucus unusually thick in several body systems.

In the airways, sticky mucus is harder for cilia to clear, so infection risk rises and blocked airways reduce gas exchange. In the digestive system, mucus can block pancreatic ducts and hinder enzyme delivery and nutrient absorption. In the reproductive system, thick mucus can obstruct sperm movement or passage.

Two unaffected carrier parents can each pass the recessive allele: the child-risk calculation is 1/4 affected, 1/2 carrier and 1/4 non-carrier. The inheritance probability and the physiological symptoms are linked but are not the same claim.

Not every CFTR mutation has an identical effect, and a recessive allele can be carried without symptoms. Explain the chain from gene to channel to water movement to system function rather than treating the disorder as only a lung disease.