Cystic Fibrosis is caused by a single faulty gene that controls the movement of salt in the body. In people with Cystic Fibrosis, the internal organs become clogged with thick, sticky mucus resulting in infections and inflammation making it hard to breathe and digest food.

For a baby to be born with Cystic Fibrosis, both parents must be carriers of the faulty CF gene. The diagram shows how CF is inherited. Where both parents carry the faulty gene, each child has a one in four chance of having CF, a two in four chance of being a carrier and a one in four chance of not having any CF genes.