Evolutionary Genetics Glossary

A heritable trait that increases an organism's fitness in its environment, or the process by which such traits evolve.

One of two or more alternative forms of a gene at a particular locus on a chromosome.

Speciation that occurs when populations are geographically separated, preventing gene flow.

Selection that maintains multiple alleles in a population, such as through heterozygote advantage or frequency-dependent selection.

A drastic reduction in population size that reduces genetic variation and alters allele frequencies.

A mathematical framework tracing alleles backward in time to their most recent common ancestor in a population.

Natural selection that favors one extreme phenotype, shifting the population mean over time.

The size of an idealized population that experiences genetic drift at the same rate as the actual population.

A gene interaction in which the phenotypic effect of one gene depends on one or more other genes.

The relative reproductive success of a genotype compared to others in a given environment.

A form of genetic drift occurring when a small group establishes a new population with reduced genetic variation.

The movement of alleles between populations through migration and interbreeding.

Random changes in allele frequencies across generations due to chance, most significant in small populations.

The reduction in average fitness of a population due to the presence of suboptimal genotypes.

A principle stating that allele frequencies remain constant in the absence of evolutionary forces.

A situation in which heterozygous individuals have higher fitness than either homozygous class.

The transfer of genes between organisms by means other than vertical inheritance, common in prokaryotes.

The non-random association of alleles at different loci on a chromosome.

A method for estimating evolutionary divergence times based on the assumption that mutations accumulate at a roughly constant rate.

Differential survival and reproduction of organisms due to differences in heritable traits.

Kimura's theory that most molecular-level evolutionary change is due to drift of neutral mutations, not selection.

A branching diagram depicting the evolutionary relationships among species or other taxa.

The exchange of genetic material between homologous chromosomes during meiosis, producing new allele combinations.

A reduction of genetic variation in the genomic region surrounding a recently fixed beneficial allele.

The evolutionary process by which new biological species arise through reproductive isolation.