Genetic association studies.

With the completion of the HapMap project1 and the development of technology that allows the examination of 1 million genetic polymorphisms at once, genetic association studies are becoming more comprehensive. This article first provides a brief overview of the rationale for genetic association studies; it then discusses the primary features differentiating genetic from standard association studies and emphasizes these differences with an example. Finally, this article reviews methods for addressing 2 of the main pitfalls of genetic association studies: population stratification and multiple testing. The principal focus of this primer is population-based association studies using unrelated individuals. A future article will address family-based linkage and association studies.