Population structure (genetics)

{{Short description|Stratification of a genetic population based on allele frequencies}}

{{Short description|Stratification of a genetic population based on allele frequencies}}

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'''Population structure''' (also called '''genetic structure''' and '''population stratification''') is the presence of a systematic difference in [[allele]] [[Allele frequency|frequencies]] between [[population|subpopulation]]s. In a [[panmixia|randomly mating]] (or ''panmictic'') population, allele frequencies are expected to be roughly similar between groups. However, mating tends to be non-random to some degree, causing structure to arise. For example, a barrier like a river can separate two groups of the same species and make it difficult for potential mates to cross; if a [[mutation]] occurs, over many generations it can spread and become common in one subpopulation while being completely absent in the other.

'''Population structure''' (also called '''genetic structure''' and '''population stratification''') is the presence of a systematic difference in [[allele]] [[Allele frequency|frequencies]] between [[Population (biology)|subpopulation]]s. In a [[panmixia|randomly mating]] (or ''panmictic'') population, allele frequencies are expected to be roughly similar between groups. However, mating tends to be non-random to some degree, causing structure to arise. For example, a barrier like a river can separate two groups of the same species and make it difficult for potential mates to cross; if a [[mutation]] occurs, over many generations it can spread and become common in one subpopulation while being completely absent in the other.

Genetic variants do not necessarily cause observable changes in organisms, but can be correlated by coincidence because of population structure—a variant that is common in a population that has a high rate of disease may erroneously be thought to cause the disease. For this reason, population structure is a common [[confounding variable]] in [[medical genetics]] studies, and accounting for and controlling its effect is important in [[genome-wide association study|genome wide association studies]] (GWAS). By tracing the origins of structure, it is also possible to study the [[genetic ancestry]] of groups and individuals.

Genetic variants do not necessarily cause observable changes in organisms, but can be correlated by coincidence because of population structure—a variant that is common in a population that has a high rate of disease may erroneously be thought to cause the disease. For this reason, population structure is a common [[confounding variable]] in [[medical genetics]] studies, and accounting for and controlling its effect is important in [[genome-wide association study|genome wide association studies]] (GWAS). By tracing the origins of structure, it is also possible to study the [[genetic ancestry]] of groups and individuals.