L41 BIOL 2970 Lecture 34: Heritability and QTLs
28 Nov 2017
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Heritability (h2) is often measured by parent-offspring correlation. Covariance -- measure phenotypes in two individuals, say x and y (parent and offspring). Correlation coefficient -- standardized covariance that varies from -1 to +1 -- biologically, we only consider 0 to +1. Fisher showed: is additive genetic variance, only 1/2 because analyze one parent at a time. Note: corr(parent,offspring) corr(sibs) e. g. systolic blood pressure: corr(p, o) = 0. 237 --> h2 = 0. 474. Tay sach"s disease -- all genetic variance is dominance variance, so disease is genetically transmitted but not heritable. Not heritable -- as long as t is rare (low q) and mating is random, tay-sachs disease is not heritable. When q is very small, almost all mating under random mating in the population are 1 of 3. When q is very small, almost all mating under random mating in the population are 1 of 3 types:
