Gel showing the genotypes for NAD(P)H:quinone oxidoreductase gene (NQO1), C609T(Pro187Ser) polymorphism by primers with different melting temperatures. Lane M contains a 100-bp DNA ladder, lanes 1 to 3 for C allele primers (F1 and R1), lanes 4 to 6 for four primers (F1, R1, F2, and R2), and lanes 7 to 9 for T allele primers (F2 and R2). PCR was conducted for template DNA from three individuals with C/C, C/T, or T/T genotype, from left to right. The annealing temperatures were 59°C (a), 61°C (b), 62°C (c), and 64°C (d).