For example, individuals with the 3849+10 kb C-T mutation exhibit a mild cystic fibrosis phenotype due to the production of mutant and wild-type CFTR mRNA (Chiba-Falek et al., 1999) and there is a case report of a homozygous affected man being fertile (Dreyfus et al., 1996). The gene discussed is CFTR; the disease is cystic fibrosis.