As it turns out, normal 5 3 polymerases are responsible for the synthesis of these Okazaki fragments.
Isolation of the fragments and digestion with 3 exonuclease revealed that the label was added at the 3 end
of the fragments, as would be expected if the DNA fragments were synthesized by poly-III or another
polymerase adding bases at the free 3 –OH end. Finally, the fragments were joined into DNA strands by a
DNA ligase enzyme, and mutants that were ligase-negative (lack a functional ligase) failed to show the
pulse-chase assembled into larger fragments