Checkpoints are surveillance mechanisms that monitor and regulate the progression of the cell cycle. The three main checkpoints are the G1/S checkpoint, the G2/M checkpoint, and the metaphase (spindle assembly) checkpoint. These checkpoints ensure that the cell is ready to proceed to the next phase, preventing errors such as DNA damage or incomplete replication from being passed on to daughter cells. For example, the G1/S checkpoint assesses DNA integrity before replication, while the G2/M checkpoint ensures all DNA is replicated and undamaged before mitosis.
