Cell cycle and DNA damage checkpoints act to halt cell cycle progression in the face of endogenous or exogenous genotoxic stress. Many proteins that enforce these checkpoints act during every cell division cycle to ensure fidelity, and also serve as important barriers to cell cycle progression under stress conditions until DNA damage is repaired. In cases of irreparable damage, the cell undergoes apoptosis.
G1 (Restriction) Checkpoint
G2/M (DNA Damage) Checkpoint
Metaphase (Mitotic Spindle) Checkpoint