PI locus (alpha-1-antitrypsin) allelic frequencies in an Andean Venezuelan population.

PI phenotypes were determined by isolelectric focusing in a Venezuelan mixed population (the center point of the geographical area investigated being Apartaderos, State of Mérida, Venezuela). Six alleles were found, four normal and two risk-predisposing with the following frequencies: PI*M1 (80.5%), PI*M2 (7.0%), PI*M3 (6.2%), an anodic allele here referred to as PI*"AN' (0.2%), PI*S (5.0%) and PI*Z (0.9%). The latter, unlike the others, was found only in 10% of the area considered, where it had a polymorphic frequency of 2.1%, reflecting a probable geographic isolation and/or a cultural influence in mating choice. In this population the alleles predisposing to risk are most probably of Caucasoid origin ("Spanish' genes). The PI*Z and PI*S frequencies may be attributed to random genetic drift characterized by an important founder phenomenon and to population admixture (Amerindian and Spanish), respectively. The PI*S allele may be considered a very good marker for the Caucasoid contribution to the overall mixed population of Venezuela.