Why cystic fibrosis only affects the caucasian population and how the disease may have originated?

not true: Cystic fibrosis is a metabolic disorder more common in caucasions by present in many populations.The incidence is 1/3500 caucasion, 1/17, 000 african american, 1/80, 000 native american. It arises in mutations in the cftr gene that regulates cellular transport of chloride.There are in excess of 700 known mutations recorded but most common is the delta 508.