gene pool

Think of every allele carried by every member of a population, all pooled together in one imaginary reservoir. That reservoir is the gene pool: the complete set of genetic variants available to a population at a given moment. Each new generation is, in effect, a draw of gametes from this pool.

Formally, a gene pool is the total collection of alleles, across all loci, present in all the individuals of an interbreeding population at a particular time. Its makeup is summarized by the allele frequencies at each locus, and its richness by how much variation it contains.

Population genetics can be read as the study of how a gene pool changes. Mutation adds new alleles to the pool, gene flow exchanges alleles with other pools, drift randomly reshuffles their proportions, and selection skews which ones are passed on. Evolution is the pool's composition shifting over time.

A deep, varied gene pool gives a population options—raw material for adapting to new diseases, climates, or competitors. A shallow one, depleted by bottlenecks or inbreeding, leaves a population more fragile, which is why conserving genetic diversity is a central goal in protecting endangered species.