Codon 89 polymorphism of the human 5alpha-steroid reductase type 2 gene.

The existence of a genetic polymorphism within the coding region of the human 5alpha-steroid reductase type 2 (5alpha-SR2) gene is reported in a Mexican population. Genotypic variation was assessed in 100 unrelated, healthy volunteers (50 males; 50 females), using single-stranded conformational polymorphism and direct sequencing analysis. Examination of exon 1 DNAs disclosed the presence of sequences encoding for valine (GTA) or leucine (CTA) at codon 89 of the gene. Of the subjects screened, 45% were homozygous for GTA (89Val), 50% had a heterozygous pattern GTA/CTA (89Val/89Leu) and the remaining 5% were homozygous for CTA (89Leu). These data support the view that the G/C condition at codon 89 of the 5alpha-SR2 gene represents a silent polymorphism which does not alter phenotypical development in the human.