A total of 5lL of PCR products were mixed with an equal volume of loading buffer (98% formamide, 0.05% bromophenol blue, 0.05% xylene cyanol, and 10 mM NaOH), denatured at 95C for 5 min, and then immediately chilled
on ice. Denatured PCR products were resolved on 6% denaturing polyacrylamide gel for 1–1.5 h. Bands were visualised using silver staining, and their sizes were estimated using a 25 bp DNA ladder standard (Promega, Madison, WI).