Final answer:
The S-Cdk helps guarantee that replication occurs only once during each cell cycle by promoting the assembly of a prereplicative complex.
Step-by-step explanation:
The S-Cdk (S-phase cyclin-dependent kinase) helps guarantee that replication occurs only once during each cell cycle by promoting the assembly of a prereplicative complex.
The S-Cdk complex phosphorylates proteins involved in DNA replication, allowing them to initiate the formation of the replication machinery. This ensures that DNA replication starts only once per cell cycle.