Figure 1.
(a) Location of genotyped polymorphisms across the cluster of CHRNA5–CHRNA3–CHRNB4 genes. The dark boxes represent exons. The hatched boxes represent 5′- and 3′-UTRs; * represents coding single nucleotide polymorphisms (SNPs). Diagram is not drawn to scale. (b) Pair-wise linkage disequilibrium among polymorphisms in the region of CHRNA5–CHRNA3–CHRNB4 genes in COGA European-American data set. Numbers in boxes represent r2 value between variants.