A HapMap harvest of insights into the genetics of common disease
J. Clin. Invest. Teri A. Manolio, et al. 118:1590 doi:10.1172/JCI34772 [Go to this article.]

Figure 3
Tag SNPs can define common haplotypes. Variable sites (SNPs) are shown by colored bars in this simplified example (adjacent SNPs are generally separated by longer distances). Complete independence of these 6 SNPs would predict the possibility of 2⁶ or 64 different haplotypes (because n biallelic SNPs could generate 2n haplotypes), but in reality just 4 haplotypes comprise 90% of observed chromosomes, indicating that LD is present. To be specific, SNP1, SNP2, and SNP3 are strongly correlated, and SNP4, SNP5, and SNP6 are strongly correlated, so that any of SNP1–SNP3 (or SNP4–SNP6) could serve as tags for the other 2 SNPs in each group. Specific tags may be chosen for genotyping platforms because of stronger associations with additional SNPs in the region or technical ease of genotyping.