Single nucleotide polymorphisms in alcohol dehydrogenase genes among some Indian populations.

Seven ADH genes, identified until now, located in the long arm of human chromosome 4, produce seven different isozymes involved in the metabolism of ethanol to acetaldehyde. Of the more than 500 SNPs reported in the coding and non-coding regions of these genes in the world databases, 11 are more extensively studied. Three SNPs, ADH1B Arg47His (Exon3), ADH1B Arg369Cys (Exon9) and ADH1C Val349Ile (Exon8), are functionally validated in terms of phenotype-genotype correlations and are in specific linkage disequilibrium (LD) with non-coding SNPs. However, the frequency of each SNP and configuration of LD varies among populations. The Indian populations studied were conspicuous by the complete absence of African specific allele ADH1B369Cys, the negligible frequency of East Asian specific ADH1B47His allele and the presence of a novel SNP ADH1B A3529G (Intron3). The ADH1C*349Ile was the only functional allele polymorphic with a strong LD block in all the populations studied and the high F(st) value observed for the non-coding ADH1B Rsa1 variant was in conformity with world populations.