Anthro Lecture 2-28

Anthro Lecture 2-28 - Anthro Lecture 2-28 I. Heritability...

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Anthro Lecture 2-28 I. Heritability (h 2 ) a. Basic Explanation i. Heritability of a trait – The proportion of phenotypic variation that is attributable to genetic variation ii. Varies from 0.00 to 1.00 iii. Vt = total phenotypic variation in a trait iv. Vg = amount of phenotypic variation due to genetic variation v. Ve = amount of phenotypic variation due to environmental variation vi. Vt = Vg + Ve vii.h 2 = Vg/Vt viii. If h 2 = 0, none of the phenotypic variation is due to genetic variation ix. If h 2 = 1, all of the phenotypic variation is due to genetic variation b. Estimating h 2 i. Comparisons between monozygotic (MZ) and dizygotic (DZ) twin pairs 1. To the extent that MZ twins are more similar, heritability is higher ii. Correlations between identical twins reared apart 1. Any similarity above chance levels implicates genetic contribution to variation iii. Comparisons between adoptive and genetic co-reared siblings 1. To the extent that genetic sibs are more similar, heritability is higher c. Use i. Developed originally to use in agriculture (breeding animals and plants) ii. Also useful for assessing the potential for natural selection to operate on a trait (remember that Darwin’s postulates include heritability)
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iii. But it is not the same as “the proportion of the trait that’s attributable to genes” which is immeasurable and meaningless iv. …specifically 1. h 2 tells you about the sources of variation among individuals, not the relative roles of genes and environment in individual development (recipe analogy) 2. h 2 is specific to a particular population at a particular point in time, because changes in either the population’s genetic make-up or its environment will change the value of h 2 . Two genetically identical populations could have different values of h 2 for the same trait v. Take-home message 1. It’s meaningless to speak of THE heritability of trait x, because h2 can
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Anthro Lecture 2-28 - Anthro Lecture 2-28 I. Heritability...

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