Human genetic variation of medical significance

Abstract

Abstract This chapter reviews evidence on medically significant genetic variation in humans. Extensive amounts of normal genetic variation occur in humans, and every independently conceived individual is genetically unique. The distribution of genetic variation in populations is the product of a human evolutionary history that has included selection and random genetic drift influenced by migration, demography, and isolation. The major features of genetic variation in modern humans are the large amount of variation in Africa and the loss of variation in the expansion out of Africa. Against the background of allele frequency variation around the world, it is difficult to identify which loci have been subject to natural selection varying among geographic regions. That normal genetic variation can affect health in surprising and complex ways is illustrated by how metabolism and taste perception are related to alcoholism.