Final answer:
The synthesis of ΦX174 RF DNA is a model for understanding lagging strand synthesis in DNA replication, involving the assembly of primosome at the pas, hairpin formation, and the action of helicase, primase, and DNA polymerases to create Okazaki fragments that are eventually joined by DNA ligase.
Step-by-step explanation:
Synthesis of double-stranded ΦX174 RF DNA is studied as a model for lagging strand synthesis, which is important in understanding the process of DNA replication.
In this process, the primosome assembles at the priming site, commonly referred to as the "primer initiation site" (pas). The pas forms a hairpin which is recognized by replication proteins.
Specific proteins such as DnaA, bind to the pas and DnaC is displaced by the PriA protein, which is responsible for primosome assembly. Then, the DnaB protein, a helicase, is recruited by PriA to propel the primosome.
Primase (DnaG) is then recruited by the helicase to synthesize short RNA primers that initiate the synthesis of DNA on the lagging strand.
During replication, single-strand binding proteins stabilize the unwound DNA, and topoisomerase prevents supercoiling ahead of the replication fork.
DNA polymerases, notably DNA polymerase III, elongate the DNA strand from the RNA primer. On the lagging strand, synthesis occurs in short stretches known as Okazaki fragments, which are later joined together to form a continuous strand.
The RNA primers are eventually replaced by DNA, with the help of DNA polymerase I, and the nicks left behind are sealed by DNA ligase to complete the replication process.