heritability

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heritability The measure of the degree to which a phenotype is genetically influenced and can be modified by selection. It is represented by the symbol h2: this equals Va/Vp where Va is the variance due to genes with additive effects (known as the additive genetic variance) and Vp is the phenotypic variance. The variance V may also be written as s2. Parent-offspring correlations, as used in studies of the heritability of human IQ, are estimates of familiality and not of heritability: they cannot account for environmental correlations between relatives. This definition of heritability is a narrow one: heritability in the broad sense (represented by H2) is the fraction of total phenotypic variance that remains after exclusion of the variance due to environmental effects.

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