and cataloging of variants, in particular single nucleotide polymorphisms (SNPs), across the genome [see the International Hapmap Project (Barrett et al., 2005) and the 1000 Genomes Project (http://www.1000genomes.org/) for details]. A SNP represents a single base pair change in the DNA sequence, which may result in a change in a gene’s protein product or expression. Most SNPs, however, have no apparent effect and reflect genetic diversity that has arisen over human history. The frequency and breadth of coverage of SNPs has enabled researchers to go beyond the candidate gene study design and has revolutionized genetic analyses.
