QUANTITATIVE GENETIC-ANALYSIS OF ARTERIAL OXYGEN-SATURATION IN TIBETAN HIGHLANDERS

This study was designed to test the hypothesis that genetic difference s inferred from biological kinship relationships among individuals con tribute to individual variation in percentage of oxygen saturation of arterial hemoglobin (Sa(o2)) in a high-altitude native population. Sa( o2) data were obtained by pulse oximetry from 354 nonpregnant, healthy Tibetan residents of Pen-Dri, two rural agropastoral villages at 3800 -4065 m altitude in Lhasa Municipal District, Tibet Autonomous Region, China. Statistical analyses of these data from 46 pedigrees tested th e hypothesis of a significant genetic contribution to Sa(o2) variation . The average Sa(o2) was 89.4 +/- 0.2%, with a range of 76-97%, Additi ve genetic effects account for 44% of the interindividual phenotypic v ariation in Sa(o2) in the sample, Complex segregation analysis and var iance decomposition analysis determined that 21% of the total phenotyp ic variation could be explained by a major gene influencing Sa(o2). Ho mozygotes for the low-Sa(o2) allele have a mean Sa(o2) of 83.6%, where as heterozygotes and homozygotes for the high-Sa(o2) allele have means of 87.6% and 88.3%, respectively. This confirms findings in another T ibetan sample and extends the known geographic distribution of the maj or gene, These results suggest the hypothesis that individuals with th e dominant allele for higher Sa(o2) have a selective advantage in thei r high-altitude hypoxic environment.