ABSTRACT
This chapter focuses on the notions of population genetics that may be useful to set up and interpret genotype-phenotype association studies. Depending on the nature of selection, its pressure is very heterogeneously distributed across genes, this explains why different structures and functions in an organism may have had a very different tempo of evolution. The present structure of a population reflects the past dynamics of its component subpopulations, and integrates the consequences of stagnations, expansions, dispersion, aggregation, migration, drastic reduction in size and extinction. Genetic variation, coupled with differential survival and reproductive fitness, has provided the basis for the evolution of all biological structures and functions through its contribution to the variability of the phenotype at all its levels from molecules to organisms. Random genetic drift refers to the time-related change of allele frequencies in a population as a consequence of chance alone, independent of natural selection.
