Events of cell cycle in S-Phase

1. DNA replication starts at origins of replication and cell cycle ensures that replication occurs once per cell cycle.

2. In late mitosis and early G1 complex of proteins known as prereplicative complex (pre-RC) assemble at origin of replication. S-Cdk activity leads to the assembly of pre initiation complex.

3. After initiation pre-RC is dismantled and cannot be reassembled until the following G1. Assembly of pre-RC is stimulated by APC thus ensuring pre-RC assembly only at late mitosis and early G1 when Cdk activity is low and APC activity is high. The events of cell cycle during S-phase has been schematically represented in Figure 4.

Figure 4: Cell cycle control of chromosome duplication.