Complex trait approaches to the analysis of behaviour in the mouse

Mouse, human and other mammalian genetics has had most of its successes in identifying genes for traits with Mendelian inheritance. These are generally rare polymorphisms, often with drastic phenotypes, which are easily followed, but most biological functions are the product of multiple genes whose products interact in a variety of ways, and much of the medically interesting phenotypic variation is likewise determined by multiple loci known as quantitative trait loci (QTL). Identifying the responsible genes for these complex (also called quantitative) traits remains extremely difficult, but methods and resources are changing quickly. There is no simple way to determine the function of the majority of genes, and complex trait genetics offers one major set of tools.