The major cystic fibrosis mutation in a British population.

We have studied 72 families with at least one child with cystic fibrosis (CF); they were referred because they had requested prenatal diagnosis in a future pregnancy. The delta F508 mutation was found in 108/140 CF chromosomes (77%). In 41/72 families (57%), both parents carried a deleted chromosome and the child was doubly deleted. In only 4 families, 2 of them being consanguineous, did neither parent carry a deleted chromosome. Meconium ileus was associated with children who were delta F508/delta F508, delta F508/non-deleted and non-deleted/non-deleted.