The International HapMap project [1],[2] documented the strong correlations between alleles at polymorphic loci in close physical proximity along human chromosomes. As a consequence it is necessary to genotype only a subset of loci to capture much of the common variation in the genome. Combined with recent technological innovations this observation has made the concept of genome-wide association (GWA) studies a reality [3],[4]. Over the few last years these studies have been very successful in uncovering new disease genes for many different complex diseases [5]. Well over 300 such loci have already been published and many more studies are currently being planned.
