Genome-wide association studies (GWAS) have pushed human genetics into a new era. Advances in technology and affordability are rapidly allowing GWAS to identify genetic variants that affect risk for human disease (http://genome.gov/26525384). GWAS have used microarrays that allow parallel assessment of hundreds of thousands of single nucleotide polymorphisms (SNPs), and now also copy number variant (CNVs). The technology of Affymetrix (http://affymetrix.com), Illumina (http://illumina.com) and Perlegen (http://perlegen.com) have been most often used for these studies. While these microarrays have been designed to efficiently explore genetic variation across the entire human genome, they each provide better coverage in some genomic regions than in others [1], [2].
