Topics in Quantitative Genetics

Abstract

An understanding of the genetics of current world populations provides the conceptual basis upon which today's genetic association studies rest. This chapter focuses specifically on gaining a basic grounding in three general topics: 1. Linkage disequilibrium (LD), the nonrandom associations of alleles. A discussion on how linkage disequilibrium varies between populations due to multiple factors, such as random drift in allele frequencies in isolated populations, population migration, admixture, and population expansion. 2. Population heterogeneity. A discussion of the effects of population heterogeneity, including population stratification, admixture, and relatedness between subjects---specifically, the distribution of marker alleles and their apparent association with each other and with causal variants, using marker data for the empirical estimation of relatedness and kinship coefficients and of identity by descent probabilities. 3. The common disease-common variant hypothesis. Arguments in favor of the common disease-common variant hypothesis and a discussion of distributions of allele frequencies for both marker alleles and causal variants.