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. Author manuscript; available in PMC: 2010 Oct 13.
Published in final edited form as: Annu Rev Genomics Hum Genet. 2008;9:403–433. doi: 10.1146/annurev.genom.9.081307.164258

Figure 3.

Figure 3

Several analyses have indicated that haplotype blocks [where single nucleotide polymorphisms (SNPs) are in strong linkage disequilibrium (LD)] extend over greater genomic distances and are more uniform in non-Africans compared to African populations. Additionally, the size and location of haplotype blocks can vary among African samples owing to the distinct demographic histories of populations from different geographic regions in Africa. The blue bars represent haplotype blocks and the thin orange bars denote regions of recombination. Vertical lines indicate SNPs and vertical arrows indicate haplotype tag SNPs (htSNPs). Because haplotype blocks are more variable in Africans compared to non-Africans, identification of htSNPs in diverse African ethnic groups and more dense tag htSNP coverage are needed to detect an association between marker(s) and disease loci in association studies.