CFTR and cystic fibrosis: Analysis of the 34 common CFTR mutations in the Russian multiethnic CF populations revealed a particularly high frequency of two mutations in the Chechen population: c.1545_1546delTA (p.Tyr515X; 1677delTA) – 52/64 CFTR alleles (81.3%), and c.274G > A (p.Glu92Lys, E92K) – 8/64 alleles (12.5%) (Table 1).