Cystic fibrosis is a genetic disease. This means that people inherit it from their parents through genes (or DNA). Genes, found in the nucleus of all the body’s cells, control cell function by serving as the blueprint for the production of proteins.
To have cystic fibrosis, a person must inherit two copies of the defective CF gene—one copy from each parent.
If both parents are carriers of the CF gene (i.e., they each have one copy of the defective gene, but do not have the disease themselves), their child will have a 25% chance of inheriting both defective copies and having cystic fibrosis, a 50% chance of inheriting one defective copy and being a carrier, and a 25% chance of not having CF or carrying the gene.
Illustration of how Cystic Fibrosis is inherited