Fig. 1

Map of M13mp18 and f1PM based heteroduplex substrates. a The map of bacteriophage M13mp18 replicative form (RF) DNA shows restriction enzyme sites relevant to this study with derivatives M13LR1 and M13LR3 containing 22-bp insertions at the unique HindIII restriction site, and phage M13WX1 and M13X22 containing 26-bp and 22-bp insertions at XbaI site respectively. b The map of bacteriophage f1PM RF DNA with its derivative f1PMA with a 27-bp insertion at XbaI. ‘V’, phage viral strand. ‘C’, phage complementary strand. Underlines beneath each viral strand are the original insertion sequences. The C-strand from parental phage RF DNA was paired with viral strand of its insertion derivative to produce gapped duplex DNA, and the gap was sealed with dI or deoxyuridine containing synthetic oligodeoxyribonucleotide. A-I, C-I, G-I, T-I, and G-U are the resulting substrates and DNA sequence shown on each C-strand of the the synthetic linker used. In the presence of dI, the substrates were refractory to the restriction endonuclease scoring. After the repair, DNA products become sensitive to restriction endonuclease cleavage. The recognition sequence of corresponding restriction endonuclease markers for repair products are shown in bold on V-strands