For all participants DNA was obtained from buccal samples [32] and DNA was extracted using standard procedures. PCR was carried out using the following conditions: initial 5-min denaturing step at 95.0 C, followed by 35 cycles at 94.0 C for 1 min, 53.8 C for 1 min and 72.0 C for 1 min 30 s, and a final extension phase at 72.0 C for 10 min. Primer sequences were those described by Sabol et al. (1998): MAO-F (5′-ACAGCCTGACCGTGGAGAAG-3′) and MAO-R (5′-GAACGGACGCTCCATTCGGA-3′). Reactions were performed in 25 µl total volume with 50 ng genomic DNA, 1.5 mM MgCl2, 10 pmoles of each primer, 0.33 mM dNTPs, and 1.5 U of native Taq (Promega, Madison, WI). PCR products were assayed on a 3% agarose gel. The primers used yielded 290, 320, 335, 350 and 380 bp fragments corresponding to the 2-, 3-, 3.5-, 4-and 5-repeat alleles, respectively [12].
