Final answer:
Primase, working with helicase, synthesizes RNA primers needed for DNA polymerase III to replicate the lagging strand in the form of Okazaki fragments. A separate primer is needed for each Okazaki fragment, and these primers are later replaced with DNA and bonded by DNA ligase.
Step-by-step explanation:
Primase forms a complex with helicase at the replication fork and moves along the template of the lagging strand. The single primer on the leading strand is probably synthesized by the primase-helicase complex on the template of the lagging strand of the other replication fork at the opposite end of the replication bubble.
DNA Replication Process
During DNA replication, helicase unwinds the DNA at the origin of replication forming a replication fork. Topoisomerase relieves the supercoiling that occurs ahead of the replication fork. At this fork, primase synthesizes an RNA primer, allowing DNA polymerase III to synthesize the new daughter strand. The leading strand is synthesized continuously, while the lagging strand is created in short fragments known as Okazaki fragments that are later joined by DNA ligase.
The continuous synthesis of the leading strand uses a single RNA primer. Conversely, each Okazaki fragment on the lagging strand begins with its own primer, requiring repeated priming events. These RNA primers are eventually replaced with DNA, and the gaps between fragments are sealed by DNA ligase to form a continuous strand.