Investigating the genetic control of complex traits (original) (raw)

Ultimately, Mendel's work was crucial to the general acceptance of Darwin's theory of evolution by natural selection. Although this was not immediately obvious when Mendel was rediscovered in the early 20 th century (Hill, 1984). Mendel had discovered that traits are inherited in a particulate or discrete manner (Moore, 2001). This upon rediscovery, rather naively offered a disparate view from Darwin's view of blending inheritance of traits (Moore, 2001), in which progeny are seen as intermediate between parents (Darwin, 1859). Trait variation, as observed by Darwin and argued by the biometricians (Hill, 1984), was a continuous progression that blended into each other gradually in an unbroken manner which makes it almost impossible to pinpoint where one becomes the next. This was a clear departure from narrow sense which includes a contribution from only the additive genetic component. Genetically, there are two categories of traits, Mendelian and complex traits, and these two categories have very different genetic architectures which make the approaches to studying and estimating their heritability also different. 1.4.1 The study of Mendelian traits The heritability of Mendelian traits has traditionally been estimated using pedigree-based studies of families with individuals affected by these conditions