Causes of cystic fibrosis
Cystic fibrosis is caused when the gene that controls the movement of salt and water in and out of the cells is faulty.
For a child to have cystic fibrosis, both their parents must carry the faulty gene. Genes come in pairs: one set is inherited from the mother and one set from the father. A child will only have cystic fibrosis if they inherit 2 faulty genes – one from their mother and one from their father.
Parents don’t always have cystic fibrosis themselves, but they can be carriers of the faulty gene. This means they have one faulty gene and one normal gene. Because you only have cystic fibrosis when you have 2 faulty genes, people with only one faulty gene have no symptoms. About 1 in 25 of us may carry the gene without knowing it.
If both parents carry the faulty gene, there is a 1 in 4 chance their child will have cystic fibrosis.