Quantitative trait locus mapping to identify genes for complex traits in Mice

Abstract

Let us say you performed a survey of five inbred mouse strains by following their body weight over time after feeding them a high fat diet. You identify three strains that became obese, whereas two strains did not. How can you identify the genes that are responsible for the different outcomes of these strains? One can apply the method of quantitative trait locus (QTL) mapping to identify the chromosomal region (locus) of a gene, or genes, that have an effect on a trait. This mapping is the first step in the identification of the responsible gene by a method that is referred to as positional cloning. In this chapter, the focus will be on the use of QTL mapping to identify genes for complex traits in mice; although, QTL mapping can be applied to any experimental system in which there is meiotic recombination and different inbred strains are available. A complex trait is a phenotype, such as body weight, that is influenced by several genes and the environment. An inbred strain contains individuals that are genetically homozygous at each locus, and thus all individuals within a strain are genetically identical. Two inbred strains may differ from each other at millions of places throughout their genomes. The goal of QTL mapping is to find the region where those differences have an effect on the phenotype. This chapter will discuss QTL mapping theory and methods, as well as several applications and emerging technology. © 2008 Humana Press.