The GWAS approach was made possible by completion of large international genomic projects beginning with the Human Genome Project (draft sequence, 2001), the HapMap Project (2003) and the 1000s genomes project (2006) which have provided an enormous amount of information on genomic variation within and between populations as well as providing the foundation for GWAS. For example, the HapMap project provided information on nearly all of the common genetic variation in humans. Approximately 1.3 million single nucleotide polymorphisms (SNPs) were genotyped in Phase I of the project, and published in 2005 (The International HapMap Consortium (2005). Phase II HapMap, characterized over 3.1 million SNPs that were genotyped in 270 individuals from four geographically diverse populations (Frazer et al., 2007). These studies enabled the use of high-throughput genotyping arrays to index millions of common SNPs across the entire genome that are then tested for association with any phenotypic trait or disease. The GWAS approach is theoretically capable of identifying all of the common genetic variants, represented by SNPs, associated with a disease or trait. This is known as the common-disease, common-variant
