Lecture 1 Introduction to Population and Quantitative Genetics

As background for the rest of the lectures in this course, our goal is to introduce some basic concepts from Mendelian genetics (the rules of gene transmission), population genetics (the rules of how genes behave in population), and quantitative genetics (the rules of transmission of complex traits, those with both a genetic and environmental basis). We start with what (at first) may seem somewhat of a digression, namely an overview of two of the most important papers in biology, those of Darwin and Mendel, which roughly appeared at the same time. Both revolutionized biology, but Mendel’s work took much longer to be accepted. Further, Darwin was concerned with traits that adapt an organism to its environment. These are usually continuous and (as we now know) result from the interaction of a number of genes coupled with the environment. In contrast, Mendelian genetics (in its initial form) was concerned with single genes that have very obvious effects on traits. The modern theory of evolution required R. A. Fisher’s classic 1918 paper showing how Mendelian genetics underpins the genetics of complex traits. Fisher’s work also introduced several important concepts in modern statistics, and it is not surprising that the analysis of complex traits (quantitative genetics) is a field rich in statistics.