Finding genes that underlie complex traits

Phenotypic variation among organisms is central to evolutionary adaptations under-lying natural and artificial selection, and also determines individual susceptibility to common diseases. These types of complex traits pose special challenges for genetic analysis because of gene-gene and gene-environment interactions, genetic heteroge-neity, low penetrance, and limited statistical power. Emerging genome resources and technologies are enabling systematic identification of genes underlying these complex traits. We propose standards for proof of gene discovery in complex traits and evaluate the nature of the genes identified to date. These proof-of-concept studies demonstrate the insights that can be expected from the accelerating pace of gene discovery in this field. A ll organisms vary in subtle and pro-found ways that involve every aspectof biological systems, including mor-phology, behavior, physiology, development, and susceptibility to common diseases. Many of these phenotypes are controlled by multi-ple genes and are therefore called multigeni