Final answer:
Simultaneous replication of the leading and lagging strands during DNA replication is made possible by the coordinated work of enzymes including primase, DNA polymerase, topoisomerase, and DNA ligase, as well as proteins like the sliding clamp that ensure efficient synthesis of new DNA strands.
Step-by-step explanation:
What allows the simultaneous replication of both the leading and lagging strands is the coordinated action of several enzymes and proteins during DNA replication. The leading strand can be synthesized continuously in the direction of the replication fork using a single RNA primer. In contrast, the lagging strand is synthesized discontinuously in the form of Okazaki fragments, each requiring a new RNA primer. The enzyme primase synthesizes these RNA primers on the lagging strand. DNA polymerase then extends these primers, adding nucleotides in the 5' to 3' direction. Topoisomerase prevents the over-winding of the DNA ahead of the replication fork. Once the fragments are synthesized, the RNA primers are replaced with DNA, and DNA ligase seals the fragments together, completing the replication process. Importantly, the sliding clamp helps to hold the DNA polymerase in place as it synthesizes new strands of DNA.