Cystic Fibrosis is an autosomal recessive disease of the exocrine glands. This means that it is NOT inherited in a sex linked pattern. It also means that to be a CF sufferer one has to inherit the mutated gene in two copies, one copy from each parent. Usually these two parents are carriers only, that is they both have the normal gene which is the dominant one and also the abnormal CF gene and usually only realise that they are both carrying the mutation when they have a CF child (25 per cent risk). They can also have normal offspring (25 per cent chance) and carrier children ( 50 per cent chance). C F children are more common in the offspring of cousins than in the general population because the cousins each receive the mutation from their shared ancestor. In the past CF children rarely made adulthood and so did not reproduce and their own mutation did not spread out but ended with them but nowadays some CF people do marry and do reproduce and so in the future the CF gene will be more common. Of course when a CF person does reproduce he/she would not necessarily have a CF child as he/she would only pass on 1 copy of one of their CF genes but their partner would be likely to be normal and not be a carrier but if they were a carrier then a CF child would be possible. C F is mainly a white childrens disease ( 1 in Two thousand births) .it is less common in Africans (1 in about 17 thousand) and almost nil in oriental children . Like other diseases like tay sachs and sickle cell are more common in other ethnic groups. Children of first cousin marriages have 8 times more chance ,approx ,of being a C F sufferer than do offspring of unrelated parents. Interestingly this is why all the pedigree dog breeds have their own specific diseases because of repeated inbreeding ,which brings the SAME recessive mutation together in the offspring.
