DNA synthesis and chromosome transfer inEscherichia coli K 12

Summary Two experiments were designed to test two alternative models of bacterial conjugation. According to the first model (Bouck andAdelberg, Nagata) the donor cell is ready for mating at the moment of completion of the chromosome replication.According to the second model (Jacob andBrenner) a special replication cycle is started during mating and the new chromosome enters the recipient cell at the same moment it was synthesized. In the first experiment synchronization ofHfr cells was used. It was shown that the efficiency of mating is constant during the whole life cycle. In the second experiment a pulse of radioactive phosphate was introduced into the mating medium. The zygotes were frozen in liquid nitrogen and the radioactive suicide of recombinants measured. Only those genetic markers, which were transmitted simultaneously with the radioactive pulse underwent radioactive suicide. Both experiments are in accord with the second model of conjugation.With 3 Figures in the Text