Genetic composition of rural Chilean communities inhabiting Elqui, Limari and Choapa valleys

Background: The population that inhabits the semiarid Northern zone of Chil e arose from ethnic admixture between aborigines, Spanish conquerors and th e influx, during the XVI century, of foreign aboriginal workers and a minor ity of African slaves. Aim: To study phenotypic frequencies of 15 genetic m arkers among populations inhabiting valles in the Northern zone of Chile an d to estimate the percentage of indigenous, African and Caucasian admixture in these populations. Material and methods: Throughout five different fiel d works, blood samples were obtained from 120 individuals living in the Elq ui valley, 120 individuals living in the Limari valley and 85 living in the Choapa valley. Blood groups, erythrocyte enzymes, plasma proteins and HLA markers were typified. Results: In the populations studied, the contributio n of non indigenous genes was low in relation with the time elapsed since t he Spanish invasion. The Hardy-Weinberg disequilibrium for MNS system would have microevolutive implications. The admixture percentages in these valle ys confirm ethnic and historic information. the variation of the enzyme est erase D is identical to that of other Chilean populations. Conclusions: The phenotypic and genetic frequencies in the three populations studied and di fferent admixture of indigenous genes is inversely proportional to the geog raphic distance from Santiago, in Central Chile.