Haplotype pattern for three SNPs in the YRI population. The vertical dark line indicates the location of the SNP (SNPid is shown). The average length of each haplotype is represented by a horizontal line. The different haplotype backgrounds carrying the derived allele are denoted by different tones of green. Each tone of gray indicates a different haplotype background carrying the ancestral allele. All haplotypes carrying the derived allele lie on the white background, whereas haplotypes carrying the ancestral allele lie on the green background.