A STUDY ON ADH2 AND ALDH2 GENOTYPING BY PCR-RFLP AND SSCP ANALYSES WITH DESCRIPTION OF ALLELE AND GENOTYPE FREQUENCIES IN JAPANESE, FINN, AND LAPP POPULATIONS

Genetic polymorphisms of the alcohol dehydrogenase ADH2 and aldehyde d ehydrogenase ALDH2 genes were investigated in Japanese, Finn, and Lapp populations by using PCR-RFLP and SSCP analyses. The ALDH2 genotypes were unequivocally determined by a PCR-RFLP assay with a mismatched pr imer. The determination of the ADH2 genotypes, however, was found to b e problematic in PCR with the reported oligonucleotide primer sets bec ause there are high homologies among the ADH1, ADH2, and ADH3 gene seq uences. The problem of the heterozygote excess in typing results obtai ned by using the previously reported PCR-RFLP methods was resolved by nested PCR, in which an internal primer set reamplified the ADH2 seque nce selectively from a mixture of the ADH gene sequences amplified in the first PCR amplification of genomic DNA samples as templates. A new ly designed primer pair with longer sequences and single 3' end mismat ches was later found to achieve a predominant amplification of the ADH 2 sequence in a single PCR. RFLP and SSCP analyses of PCR products wit h the new primer set gave results fully consistent with those by neste d PCR. Thus, the ADH2 genotypes defined in this study were free from a ny typing errors. The ADH2 and ALDH2 allele frequencies observed in th is study were found not to be biased significantly from those reported previously from Japanese populations, and these were monomorphic for Lapp and Finn populations.