Final answer:
DNA polymerase III moves independently as a molecular motor, dissociating and reassociating at new primer sites to synthesize Okazaki fragments on the lagging strand. The sliding clamp ensures the polymerase stays in place during synthesis, and DNA ligase joins the fragmented strands.
Step-by-step explanation:
The movement of DNA polymerase III during DNA replication is key to understanding how the replication of the lagging strand occurs. DNA polymerase III extends new DNA strands by adding nucleotides in a 5' to 3' direction. Concerning the lagging strand, which is synthesized discontinuously in small fragments known as Okazaki fragments, the DNA polymerase III moves independently like a tiny molecular motor. It does not hitch a ride with another polymerase or require a protein complex called the transportosome to move. Instead, it can dissociate from the DNA after completing an Okazaki fragment and then reassociate at a new primer site closer to the replication fork to start synthesis of the next fragment.
A protein called the sliding clamp plays a crucial role in holding the DNA polymerase in place as it adds nucleotides. Once an Okazaki fragment is completed, the sliding clamp releases the polymerase, which then can move to the next RNA primer to begin synthesis of the next Okazaki fragment. This process allows the lagging strand to be synthesized in segments that are later joined together by the action of DNA ligase, resulting in a complete and continuous DNA strand.