Role of S -CDK

S-Cdk (S-phase Cyclin-Dependent Kinase) initiates and regulates DNA replication during the S phase of the cell cycle. It activates the pre-replicative complexes (pre-RCs) assembled during G1 phase by phosphorylating key replication proteins. This recruits DNA replication enzymes to replication origins and starts DNA synthesis. S-Cdk also prevents the formation of new pre-RCs after replication begins, ensuring that each DNA segment is replicated only once per cell cycle. Thus, S-Cdk guarantees accurate and complete duplication of the genome before cell division.