Dictionary of Human Evolution and Biology

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Twin Study

Any of a series of research projects carried out since the nineteenth century work of Francis Galton that attempt to estimate the heritability of a complex phenotypic trait. Such studies operate under the assumption that all twin pairs are of only two modalities (monozygotic twins, MZT, or dizygotic twins, DZT), that twin zygosity can always be correctly ascertained, and that the average proportion of genes shared by MZT twins is 100% whereas for DZT twins it is 50%.

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