The defective CFTR gene produces a faulty protein that affects the movement of chloride - a component of salt, or sodium chloride - across cell membranes, according to the Cystic Fibrosis Foundation. If both parents are carriers of cystic fibrosis and have a child, there is a 1 in 4 chance that the child will have the disease, Fracchia told Live Science. Carriers don't have any symptoms of cystic fibrosis, but they can pass the CFTR gene on to their children. People who have one copy of the defective CFTR gene, inherited from only one parent, become carriers of the disease. People with cystic fibrosis have a mutation in both copies of the CFTR gene (one copy inherited from each parent). This defective gene, called the cystic fibrosis transmembrane conductance regulator (CFTR), was first identified in 1989, according to the Cystic Fibrosis Foundation. The cause of cystic fibrosis is genetics, because a person needs to inherit a copy of a defective gene from both parents to develop the condition, Fracchia said.
In some people, cystic fibrosis also harms the liver and reproductive system.