Fig. 1

Diagram of locations of all tag-SNPs and other SNPs in the four genes chosen for study. The AHR gene, having 11 exons, is located on chromosome 7p15, and the transcribed region spans 47.53 kb; 16 tag-SNPs inside or near the gene were selected. CYP1A1 (spanning 6.07 kb) and CYP1A2 (7.36 kb) on chromosome 15q24.1 each have seven exons and are arranged in tandem, head-to-head, with a 23.3-kb bidirectional promoter between them; four tag-SNPs inside and near each gene were chosen. Human CYP1B1 on Chr 2p22.2 has three exons and spans 8.68 kb; 12 tag-SNPs inside and near the gene were selected. Note that three SNPs (#2, 3 and 4) are located in CYP1B1 exon 3, within four nucleotides of one another. Closed rectangles of the exons denote the translated region and open rectangles the 5′- and 3′-untranslated regions. Whereas translation of AHR is initiated at the 3′ end of exon 1, all three CYP1 genes have noncoding first exons. Note that CYP1A1 and CYP1B1 are on reverse strand of gDNA, meaning that the chromosomal location of each SNP for these two genes in the Genome Assembly is numbered from the 3′- to 5′-end, whereas AHR and CYP1A2 are on the positive strand and therefore each SNP for these two genes is numbered from the 5′- to 3′-end.