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.