The study of twins / Peter Mittler.

  • Mittler, Peter J.
Date:
[1971]
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: The study of twins / Peter Mittler. Source: Wellcome Collection.

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    169 Heritability estimates Table 31 Partitioning of Components of Variance between and within Pairs of Twins where Vg = additive genetic variance. Fee = variance between pairs due to common environment between pairs. Few = variance due to environmental differences between pairs. Source: Falconer (1960) The derivation of a heritability formula follows from this argument. Since the difference between ^dz stitutes half the genetic variance, the total genetic variance is given by the formula = 2(rj^2 ~ ^Dz)* Three other formulae have also been proposed recently by Jensen (1967), Nichols (1965) and Vandenberg (1965). Jen¬ sen's formula is virtually identical to Falconer's, but is notable for the addition of some important refinements such as an estimate of the proportion of the total variance due to systematic (between families) environmental differences (E^), and also due to unsystematic (within families) environ¬ mental variance (e^). His formula is essentially L2 _ ^MZ ~ ^DZ 1 ♦ 1 ''sg where = the genetic correlation between siblings. Since rgg is normally 0-50, the formula becomes identical to Falconer's