Bridging Genotype and Phenotype: Causal Pathways from DNA to Complex Traits

High-throughput molecular profiling technologies such as microarrays have recently been used in the genetic analysis of complex traits. Genetic loci influencing gene expression can be identified using quantitative trait locus (QTL) mapping. These genetic loci may also influence higher-order traits. The coregulation of gene expression traits and higher-order traits indicates that some of the gene expression traits may be involved in the causal pathways connecting the genetic loci and higher-order traits. Strong associations between the modules of gene expression traits, higher-order traits, and the genetic loci regulating them have been found, indicating that genetic loci may influence higher-order traits by affecting gene expression traits. In this chapter, I discuss the recent trend in combining genetic and genomic methods to analyze complex traits, and introduce a computational approach to studying the causal pathways from DNA to complex traits.