Cell membrane

, Airways

Mucus-clogged bronchi and bronchioles. Respiratory infections. (Common)


Blocked small bile ducts impair digestion. (Rare)


Blocked ducts prevent release of digestive enzymes, impairing fat digestion. Diabetes is possible. (Common)


Hard stools may block intestines. (Rare)

Reproductive tract

Absence of vas deferens. (Common)


Salty sweat. (Common)

Cystic fibrosis transmembrane conductance regulator (CFTR) protein


From gene to protein to person. (a) The gene encoding the CFTR protein, and causing cystic fibrosis when mutant, is on the seventh largest chromosome. CFTR protein folds into a channel that regulates the flow of chloride ions into and out of cells lining the respiratory tract, pancreas, intestines, and elsewhere. (b) In cystic fibrosis, the CFTR protein is abnormal, usually missing an amino acid. Its shape is altered, which entraps the chloride ions inside cells. Water entering these cells leaves behind very thick mucus and other secretions in the places highlighted in the illustration. The sticky secretions cause the symptoms of the illness.

Source: Data from M.C. lannuzi and F.S. Collins, "Reverse Genetics and Cystic Fibrosis" in American Journal of Respiratory Cellular and Molecular Biology, 2:309-316, 1990.

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