PCR amplification was conducted in a total volume of 10 ml with 10 ng of template DNA, 2 ml of 10 buffer , 0.4 mM dNTPs, 10 mM MgCl2, 0.5 U of Taq DNA polymerase , 0.05 mM forward primer, 1.5 mM reverse primer, and 1.5 mM fluorescently labelled M13 primer.