Individual genes underlying quantitative traits: molecular and analytical methods.

Because of innovations in quantitative and molecular genetics, it is becoming possible to study the individual loci affecting quantitative traits, quantitative trait loci (QTL). We review a number of recently developed molecular and analytical techniques that allow the identification and localization of QTL and the quantification of their effects, and present an example. We suggest that this area of investigation, already in widespread use in the agricultural and medical sciences, will become increasingly important in evolutionary biology as techniques continue to improve.