Lecture 16

While the machinery of quantitative genetics can blissfully function in complete ignorance of any of the underlying genetic details, we are certainly interested (at least one some level) in the genetic basis of trait variation. At the most practical level, if a gene of major effect is segregating in our population of interest, we would certainly like to be aware of this, as well as being able fine map it for future exploration/exploitation. Often no single locus contributes more than a fraction of the total genetic variation in a trait. In such cases, we often use the term polygene for one of these loci of small effect. The (still evolving) more modern use is to call these genes quantitative trait loci, or simply QTL or QTLs for short. Lecture 16 deals with statistical approaches for QTL mapping, while we focus here first on the genetic basis of quantitative trait variation, and then on methods for first detecting and then fine mapping genes of large effect. Included as a special case of the later are so-called candidate genes, loci for which we have biological information to suggest that they may contribution variation to the trait of interest.