Genotypic single-point association test results and LD over NRG1. In the plot of -log10(P) v. map position, horizontal dashed lines are at P = 0.05, 0.01 and 0.001. Vertical dashed lines are at 20 kb intervals. The region covered by the gene is indicated in the centre of the figure by a horizontal line, with an arrow head indicating the direction of transcription. A crossing vertical line indicates the position of each exon. At the base of the figure, LD between SNP loci is indicated by shading. White: r2 = 0; black: r2 = 1.