GG) tags a large region previously associated with both alcohol and risk behaviors (Villafuerte, Strumba, Stoltenberg, Zucker, & Burmeister, 2013), which was genotyped by TaqMan (Villafuerte et al., 2012). Genotyping of the DRD4 48 bp variable number of tandem repeat (VNTR) in exon 3 was performed by PCR and resolved on agarose gel following reommended methods (Lichter et al., 1993). DRD4 genotypes were classified in two groups consistent with previous work: repeats 2 to 6 (short allele; 63.9% [311]) and repeats 7 or more (long allele; 36.1% [176]). The promoter polymorphism (5-HTTLPR) of SLC6A4 was genotyped by PCR following recommended methods (Sen et al., 2004). The S allele (SS 15.6% [76], LS 51.1% [249]) corresponds to a product of 14-repeat, and the long allele (LL; 33.3% [162]) reflects the 16-repeat. No deviation from Hardy-Weinberg Equilibrium was detected and no discrepancies in duplications were observed. See Table 1 for additional information on genetic variants of interest for the current study.
