G2 to M Phase Progression

At the end of S phase, cyclin A is associated with Cdk1 and Cdk2. During G2 phase, cyclin A is degraded, while cyclin B is synthesized and cyclin B-Cdk1 complexes form. Not only are cyclin B-Cdk1 complexes important for the transition into M phase, but these CDKCs play a role in the following regulatory and structural processes

1. Chromosomal condensation
2. Fragmentation of Golgi network
3. Breakdown of nuclear lamina

  Inactivation of the cyclin B-Cdk1 complex through the degradation of cyclin B is necessary for exit out of the M phase of the cell cycle.