To determine the nature and frequency of non-delta F508 cystic fibrosis (CF) 
mutations among diverse populations, we have sequenced exons 9-12 and 19-23 of 
the CF transmembrane conductance regulator (CFTR) gene from 128 CF chromosomes 
(39 U.S. Caucasian, 27 African-American, 42 Northern Irish, and 20 Israeli 
chromosomes). These regions were chosen because they encode the two putative 
ATP-binding folds of CFTR, domains which appear to have functional significance. 
In addition, CFTR exons 1 and 2 were analyzed in the American patients. 
Mutations were found on 49 of the 128 CF chromosomes. Nineteen different 
mutations were observed; six were novel, while the remaining 13 had been 
reported previously by our group or by other investigators. Six of nine 
different mutations found in African-American patients were unique to that 
population. However, the vast majority of the mutations found in U.S. Caucasians 
(eight of nine), Northern Irish (four of five), and Israelis (three of three) 
also occurred in other Caucasian groups. The preponderance of previously 
reported mutations in these three groups suggested that a subset of the 
non-delta F508 mutations occur in common among Caucasians. A survey of mutation 
frequencies in other Caucasian groups confirmed this observation. Unfortunately, 
this subset accounts for less than half of non-delta F508 CF mutations in most 
groups. These data suggest that screening for delta F508 and this select group 
of mutations will efficiently and economically maximize the number of CF 
mutations identified in Caucasian groups. However, it will be difficult to 
detect more than 90% of mutant CFTR alleles except in ethnically and 
geographically discrete populations where CF is the result of founder effect.