Cystic fibrosis (CF) is caused by a defect in a gene called the cystic fibrosis transmembrane conductance regulator () gene. This gene makes a that controls the movement of salt and water in and out of the cells in your body. In people with CF, the gene does not work effectively. This causes the thick, sticky mucus and very salty sweat that are the main features of CF. Each of us inherits two CFTR , one from each parent. CF carriers: * Usually have no symptoms of CF * Live normal lives * Can pass the abnormal CFTR gene on to their children