Allele frequency plot of a normal sample (NA19206) from the YRI population based on the Affymetrix Human Mapping 100K Set. This figure consists of 23 subfigures. Each subfigure presents an allele frequency plot for one chromosome. The vertical axis is the estimated individual-level allele frequency, and the horizontal axis is physical position (Mb). Each point denotes a SNP, and the gap in each subplot represents the centromeric gap. Individual-level allele frequencies of SNPs on each chromosome were close to the expected values of 0, 0.5 and 1.