Quantitative genetics: Introduction
We switch gears completely today. When we've talked about phenotypes (and we've mostly ignored them), we assumed that they were associated with genotypic differences at a single locus. Today we'll start developing the ideas underlying one approach to understanding the genetic basis of phenotypic evolution. You've probably heard the words "heritability" and "additive genetic variance," but I suspect that even if you know there's a difference between narrow-sense and broad-sense heritability or between additive and dominance genetic variance, that you don't really understand what those differences are. Well, over the course of the next few lectures, you will - and you'll get to see where the breeder's equation (R = h2S) comes from. As a bonus, we'll derive Fisher's Fundamental Theorem of Natural Selection. We'll finish off with some modern approaches to understanding the genetics of quantitative traits that take advantage of the advances in molecular genetics we just finished discussing.