Genome-wide association studies: present status and future directions.

Genome-wide association studies (GWAS) involve the genotyping of large case-control cohorts using array-based genotyping platforms typically including several hundred thousand markers. The application of GWAS to a large number of different phenotypes of interest (often specific diseases) in recent years has resulted in the identification of an enormous number of associated loci, which have dramatically advanced understanding of genetic factors contributing to human disease. In this review, the genetic architecture of human disease is addressed and the technical features of GWAS are described. Next, approaches for defining the biologic basis for GWAS signals are described. The future challenges of developing improved phenotypic definitions for complex traits are also discussed.