MITOCHONDRIAL-DNA ANALYSIS IN TIBET - IMPLICATIONS FOR THE ORIGIN OF THE TIBETAN POPULATION AND ITS ADAPTATION TO HIGH-ALTITUDE

Mitochondrial DNAs (mtDNAs) of 54 Tibetans residing at altitudes rangi ng from 3,000-4,500 m were amplified by polymerase chain reaction (PCR ), examined by high-resolution restriction endonuclease analysis, and compared with those previously described in 10 other Asian and Siberia n populations. This comparison revealed that more than 50% of Asian mt DNAs belong to a unique mtDNA lineage which is found only among Mongol oids, suggesting that this lineage most likely originated in Asia at a n early stage of the human colonization of that continent. Within the Tibetan mtDNAs, sets of additional linked polymorphic sites defined se ven minor lineages of related mtDNA haplotypes (haplogroups). The freq uency and distribution of these haplogroups in modern Asian population s are supportive of previous genetic evidence that Tibetans, although located in southern Asia, share common ancestral origins with northern Mongoloid populations. This analysis of Tibetan mtDNAs also suggests that mtDNA mutations are unlikely to play a major role in the adaptati on of Tibetans to high altitudes. (C) 1994 Wiley-Liss, Inc.