Manhattan plot of P -value for quantitative trait GWAS using best race distance as phenotype. The y-axis plots -log10(P-values) and the x-axis plots the physical position of the SNPs sorted by chromosome and chromosome position. A peak of association on chromosome 18 (chr18:65809482-67545806) encompassed a ~1.7 Mb region (shown in Figure 3). Seven of the chromosome 18 SNPs remained significant following correction for multiple testing. The most significant SNP was BIEC2-417495 (PBonf. = 6.58 × 10-5).