the.com/gene pool

All the genes and variations shared within a breeding population, passed on to future generations.

means The total collection of genes and their variations present in an interbreeding population, representing all the hereditary possibilities available to future generations.

from A 20th-century coinage from population genetics, built simply from 'gene' (coined in the early 1900s from Greek 'genos,' meaning birth or race) plus 'pool,' used in its sense of a shared, communal reserve — like a betting pool or car pool. The metaphor imagines all the genetic variants in a breeding population as liquid assets sloshing around together, mixing and recombining with each generation rather than belonging to any one individual.

metaphor
A figure of speech; the genes are not in a pool
size matters
smaller pools breed more recessive disorders
misuse
The phrase has been misused to argue that some people should be excluded, which is not what it means
always refilling
mutation and migration top it up constantly
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