Effect of SNP position on SFP identification. The positions of the SNP in 25mers are shown on the x-axis as distance from the edge in nucleotides (1 - 13 nucleotides). Multiple SNP category is provided separately by a single column. The y-axis indicates total number of probes identified for each SNP position. Each bar is divided into the SFP categories - mxSFP, nonSFP and gpSFP (see Table 2), and shows that more accurate SFP identification is made for SNPs that reside at internal sites. The number of 25mers in each category is shown within the bars.