Fig. (3) Native polyacrylamide gel electrophoresis of DNA fragments containing an IS10 target site. DNA fragments obtained by PCR amplification were electrophoresed on native 5% polyacrylamide gel at 4°C. Lane 1, a 257-bp fragment spanning positions 1661 to 1917 of pUC19; lane 2, a 257-bp fragment spanning postions1621 to 1877 of pUC19; lanes 3, a 257-bp fragment spanning positions 1541 to 1797 of pUC19; lanes M, 100-bp DNA ladder size markers. Because the difference in the electrophoretic mobility was subtle, DNA samples were applied to the gel in duplicate. The respective DNA primer pairs used for the PCR were: 1661-CTACACGACGGGGAGTCAGGCAA CTAT (forward) and 1917-AAGAAGATCCTTTGATCTTTTCTACGG (reverse); 1621- CACTGGGGCCAGATGGTAAGCCCTCCC (forward) and 1877- GTGGAACGAAAACTCACGTTAAGGGAT (reverse); and 1541- GCGCTCGGCCCTTCCGGCTGGCTGGTT (forward) and 1797- AATGAAGTTTTAAATCAATCTAAAGTA (reverse). The IS10 target site is 1771-TACTTTAGA-1779 of pUC19.