The advent of the genome-wide association studies (GWAS) brought increased genomic density and large data sets. GWAS relied on the completion of the International HapMap Project in 2005, in which common SNPs were mapped tightly throughout the genome. Using a case-control design and hundreds of thousands of SNPs spanning the entire genome, GWAS looked for association between SNPs and disease. Although there are more statistical tests of association (1 test per SNP) than there are subjects (typically thousands), the combination of setting a sufficiently low threshold for P value significance and placing a high emphasis on replication of significant results in independent data sets has resulted in discovery of robust associations.
