DIAGNOSIS

Cystic fibrosis is a genetic disease. People with CF have inherited two copies of the defective CF gene - one copy from each parent. Both parents must have at least one copy of the defective gene.

Cystic fibrosis is a genetic disease. People with CF have inherited two copies of the defective CF gene -- one copy from each parent. Both parents must have at least one copy of the defective gene.
People with only one copy of the defective CF gene are called carriers, but they do not have the disease. Each time two CF carriers have a child, the chances are:

25 percent (1 in 4) the child will have CF
50 percent (1 in 2) the child will be a carrier but will not have CF
25 percent (1 in 4) the child will not be a carrier and will not have CF

The defective CF gene contains a slight abnormality called a mutation. There are more than 1,700 known mutations of the disease. Most genetic tests only screen for the most common CF mutations. Therefore, the test results may indicate a person who is a carrier of the CF gene is not a carrier.