The cell cycle is regulated by checkpoints.

Interphase contains two growth sub-phases (G1 and G2) separated by a S (DNA synthesis) sub-phase.

The checkpoints at G1, G2, and M (mitosis) ensure that a particular phase is completed before advancing to the next phase.

If a cell does not pass any of these checkpoints, mitosis will not proceed.

Breakdown in checkpoint regulation during the cell cycle may lead to cancer.