Illustration of the SLC6A1 LD structure and recombination hotspots in the 5 populations. Upper graphs illustrate elevations from the background recombination rates across the SLC6A1 gene. Y axis represent recombination rate and X axis represents physical distance between the markers [19, 20]. In Figure A, recombination rates for HapMap CEPH Western Europeans (CEU) and European-Americans of the present study are presented. In Figure B, recombination rates for HapMap Yoruban (YRI) and African-Americans of the present study are presented. In Figure C, recombination rates for HapMap combined Han Chinese and Japanese populations (HCB+JPT) and the Thais of the present study are presented. In Figures D and E, recombination rates for the Finns and Hmongs of the present study are presented. In the middle, the exon-intron structure of SLC6A1 and location of the markers is presented. LD (D') between the SNPs in SLC6A1 is illustrated in the lower triangular graphs.