Population Genetics Glossary

The proportion of a specific allele among all allele copies at a given locus in a population.

Non-random mating in which individuals preferentially mate with others that are similar (positive) or dissimilar (negative) to themselves for a given trait.

Natural selection that maintains genetic polymorphism through mechanisms such as heterozygote advantage, frequency-dependent selection, or varying selection across environments.

A sharp reduction in population size that reduces genetic diversity and increases the influence of genetic drift.

The merging of two lineages into a single ancestral lineage when traced backward in time, forming the basis of coalescent theory.

Selection that consistently favors one extreme phenotype, shifting the population mean in one direction over time.

The size of an ideal Wright-Fisher population that would experience the same amount of genetic drift as the observed population.

The interaction between genes at different loci where the effect of one gene depends on the presence of other genes, complicating the prediction of phenotype from genotype.

The relative reproductive success of a genotype, measured as its contribution of offspring to the next generation relative to other genotypes.

The state in which one allele has reached a frequency of 100% in a population, eliminating all other alleles at that locus.

A form of genetic drift that occurs when a small group of individuals establishes a new population with reduced genetic diversity relative to the source population.

A form of selection in which the fitness of a phenotype depends on its frequency in the population, often favoring rare phenotypes (negative frequency dependence).

The movement of alleles between populations through migration, which tends to homogenize allele frequencies and counteract differentiation.

Random fluctuations in allele frequencies across generations due to finite population size, independent of the alleles' effects on fitness.

The proportion of individuals in a population that carry a particular genotype at a given locus.

A state in which allele and genotype frequencies remain constant across generations, serving as the null model of population genetics.

The proportion of heterozygous individuals in a population at a given locus, used as a measure of genetic diversity.

Mating between related individuals, which increases homozygosity and the probability of offspring inheriting identical alleles by descent.

The reduction in fitness of a population due to increased homozygosity from inbreeding, which exposes deleterious recessive alleles.

The non-random statistical association of alleles at two or more loci, often due to physical proximity on a chromosome, selection, or recent admixture.

The movement of individuals between populations, resulting in gene flow that alters allele frequencies in both source and recipient populations.

The frequency at which new mutations occur at a locus or across the genome per generation, providing the raw input for genetic variation.

Kimura's theory that most molecular evolutionary changes are caused by random drift of selectively neutral mutations rather than by natural selection.

The reduction of genetic diversity surrounding a locus that has undergone recent strong positive selection, as linked neutral variants hitchhike to fixation.

An idealized mathematical model of a finite population with discrete non-overlapping generations, random mating, and constant population size, used to study genetic drift.