All DNA polymerases synthesize new DNA strands in the 5’?3’ direction. In some respects, replication of the antiparallel strands of duplex DNA would be simpler if there were also a second type of polymerase, one that synthesized DNA in the 3’?5’ direction. The two types of polymerase could, in principle, coordinate DNA synthesis without the complicated mechanics required for lagging strand replication; however, no such enzyme has been found. Suggest a possible mechanism for 3’?5’ DNA synthesis (show the electron pushing-you may use abbreviated structures). Pyrophosphate should be one product. If the 3’?5’ polymerase existed, could your mechanism be supported in a cell (why or why not)? [You may suggest the use of DNA precursors not actually present in extant cells.]