Allele frequencies for the 17 SNPs are presented in Table 2. Low frequency SNPs (minor allele frequency <10%), including rs11569715 (marker 7), rs11569720 (marker 8), rs3218737 (marker 9) and rs5031015 (marker 11)m were excluded from family-based analyses in both AAs and EAs and rs739368 (marker 5) was excluded only from the EA family-based analysis. The LD structure of the COMT gene reconstructed by family-based SNP data set using HAPLOVIEW program (Barrett et al., 2005) is presented in Figure 2. According to the criteria of Gabriel et al. (2002), there were three and two small blocks of LD (less than or equal to 1 kb) observed in AA and EA family populations, respectively. The first block is found only in AAs, and it spans rs5993883 (marker 4) and rs739368 (marker 5). The second LD block spans rs4680 (marker 12) and rs4646316 (marker 13) in AAs, but rs2239393 (marker 10) and rs4680 (marker 12) in EAs. The third LD block, observed in both populations, spans rs9332377 (marker 16) and 165599 (marker 17).
