Rs921451

per OMIM, Ma et al. (2005) found two different DDC haplotypes associated with nicotine dependence in African Americans and European Americans (with measures of smoking quantity [SQ], heaviness of smoking index [HSI], and the Fagerstrom test for ND [FTND])
 * in African Americans, rs921451(T), rs3735273(G), rs1451371(T), rs2060762(G), all three measures sig. associated after correction for multiple testing
 * in European Americans, rs921451(T), rs3735273(G), rs1451371(T), rs3757472(G), which showed a sig. assoc. w/ the SQ and FTND score