Final answer:
The leading strand is synthesized continuously, whereas the lagging strand is produced in Okazaki fragments due to the directional limitation of DNA polymerase. RNA primers are replaced with DNA, and DNA ligase seals the fragments on the lagging strand.
Step-by-step explanation:
The presence of a leading and lagging strand in DNA replication is due to the unidirectional nature of DNA polymerase, which can only synthesize DNA in the 5' → 3' orientation. The leading strand is synthesized continuously in the direction of the replication fork. In contrast, the lagging strand, which is constructed in the opposite direction, requires multiple RNA primers and is synthesized in short segments known as Okazaki fragments.
Furthermore, the sliding clamp protein maintains DNA polymerase's position during strand extension. Topoisomerase prevents over-winding of the DNA helix ahead of the replication fork. The discontinuous synthesis of the lagging strand and its subsequent joining by DNA ligase ensures that both strands are replicated in concert, despite the antiparallel nature of the double helix.