Population Genetics
Introduction
Population genetics is a subfield of genetics that deals with genetic differences within and between populations. It is the study of the distribution and change in frequency of alleles within populations, and as such it sits firmly within the field of evolutionary biology. The primary drivers of such changes are mutation, gene flow, genetic drift, and natural selection.
History
The field of population genetics was established by the work of Mendel, Morgan, and others. However, it was not until the work of Fisher, Haldane, and Wright in the early 20th century that population genetics became a formalized science. These pioneers combined Mendelian genetics with natural selection to create the modern synthesis, which is the foundation of population genetics today.
Genetic Variation
Genetic variation is a measure of the genetic differences that exist within a population. The presence of genetic variation implies that individuals of the population vary in their genetic makeup and therefore in their phenotypes. This variation can be caused by mutation, gene flow, or recombination.
Hardy-Weinberg Principle
The Hardy-Weinberg principle is a foundational concept in population genetics. It states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences. These influences include mutation, gene flow, genetic drift, and natural selection.
Genetic Drift
Genetic drift is a mechanism of evolution that causes random changes in allele frequencies. It occurs in all populations but is most pronounced in small populations. Genetic drift can lead to the loss of genetic variation within populations and the fixation of alleles.
Gene Flow
Gene flow is the transfer of genetic variation from one population to another. If the rate of gene flow is high enough, then two populations can effectively become one large population.
Natural Selection
Natural selection is the process by which certain traits become more or less common in a population due to the effects of those traits on the survival and reproduction of their bearers. It is a key mechanism of evolution and a central concept in population genetics.
Mutation
Mutation is a change in the genetic material of an organism. It is the ultimate source of all genetic variation. In population genetics, the mutation rate is a critical parameter that determines the rate at which new genetic variation is introduced into a population.
Genetic Linkage
Genetic linkage is the tendency of alleles that are close together on a chromosome to be inherited together. Genetic linkage is an important concept in population genetics because it can lead to the maintenance of genetic variation and the evolution of complex traits.
Population Structure
Population structure refers to the organization of genetic diversity within and between populations. Understanding population structure is critical for studying the genetic basis of complex traits and for managing genetic resources in conservation biology.