Population genetics

Population genetics studies genetic variation within and between populations and how mutation, selection, migration, and genetic drift change it over time.

Genetic drift: Random changes in allele frequencies caused by chance differences in survival and reproduction. It changes variation without favoring alleles for their effects on fitness.
Allele frequency: The proportion of copies of a gene in a population that carry a particular allele. Changes in this quantity summarize many evolutionary shifts.
Coalescent theory: A mathematical framework that traces sampled gene copies backward to their shared ancestors. It connects present-day genetic samples to past population size and ancestry.
Quantitative genetics: The study of the genetic and environmental contributions to variation in measurable traits. It focuses on trait distributions, while population genetics often tracks variants and their frequencies.
Natural selection: Differences in survival and reproduction that cause heritable traits to become more or less common. It shifts allele frequencies when genetic variants affect reproductive success.
Genotype frequency: The proportion of individuals in a population with a particular combination of alleles at a locus. It links allele frequencies to observable patterns of inheritance and mating.
Effective population size: The size of an idealized population experiencing the same genetic drift or inbreeding as a real population. It helps infer how strongly chance and demographic changes shape variation.
Molecular evolution: The study of evolutionary change in DNA and protein sequences over time. It covers sequence evolution across lineages as well as variation within populations.
Gene flow: The movement of alleles between populations through migration and reproduction. It transfers variation among populations and can reduce their genetic differences.
Locus (genetics): A specific position or region on a chromosome where a genetic sequence is located. Population comparisons track variants at loci across individuals and groups.

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