Regional association plot highlighting the genomic region of the locus selected from discovery GWAS for replication. Recombination rate and linkage disequilibrium with SMAD6 rs12438941 (red diamond) shown for chromosome 15 using SNP Annotation and Proxy Search. Case-parent trio GWAS results were used to derive the P values used to create the figure. Each square represents a specific SNP in the genomic region, and the color of the filled squares depicts the r² between that SNP and the most strongly associated SNP in our study population; the more highly correlated a SNP is with our locus of interest, the redder the box coloration. The blue lines indicate the recombination rate of this genomic region in the 1000 Genomes CEU (Northern Europeans from Utah) population.