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Genetic variation and adaptation in the Quechua, a high altitude native population Rupert, James L.

Abstract

Human adaptation to high altitude involves a suite of physiological and anatomical characteristics designed to facilitate the uptake, transport and utilization of oxygen, thereby compensating for the diminished oxygen availability inherent to high altitude. While many of these characteristics may be acclimatory or developmental in nature, there is evidence that some are influenced by the genetic background of the population. The studies presented in this thesis are designed to examine the influence of genotype by comparing the frequencies of variants in a number of candidate genes between the Quechua, a high altitude population indigenous to Andean altiplano, and two low altitude populations: Na-Dene from the west coast of Canada and Caucasians of western European descent. Genes were chosen because they had previously characterized polymorphisms with phenotypes that a priori were judged to be of potential benefit at altitude and include: 1) the β2-adrenergic receptor, the principle pulmonary catecholamine receptor; 2) angiotensin converting enzyme, a regulator of systemic blood flow; 3) β-fibrinogen, a common plasma protein and primary determinant of plasma viscosity; 4) erythropoietin, a hormone involved in the synthesis of red blood cells and 5) hypoxia inducible factor 1-alpha, a major component in oxygen-dependent gene regulation. Given the theoretical requirements of high altitude populations and the phenotypes associated with these alleles of these genes, predictions were made as to which alleles should have been selected for, and therefore currently be over-represented, in the Quechua. As expected, given the diverse origins of the populations examined, there were significant differences in haplotype structure and allele frequencies. While some of these differences may have resulted from the random divergence of separated populations over time, others, such as the under-representation of alleles associated with increased fibrinogen may reflect an adaptive change in the Quechua. Successful expansion into a demanding environment will often be reflected in the genetic make-up of a population. Previous studies investigating the role of genetics in high altitude adaptation have concentrated on the heritability of complex traits. The work presented in this thesis represents an alternate approach, one in which the focus is on the frequencies of variants in individual genes in an altitude-adapted population.

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