Quantitative genetics: resemblance among relatives
We now know how to partition genetic variation into additive and dominance components, if we know the genotypic values and allele frequencies. Of course, if we knew those things, we wouldn't have to bother with any of this. So today we come full circle. I'll illustrate how something we can estimate, the phenotypic covariance between half-sibs, is related to something we're interested in, the additive genetic variance, meaning that we can estimate Va without knowing anything about genotypic values or allele frequencies.
We'll do that derivation in detail. I'll merely mention the results for some other degrees of relationship. I will, however, show you another way to estimate heritability, namely a mid-parent offspring regression.