Which checkpoint ensures the DNA is undamaged after replication?

The G2 checkpoint is crucial in the cell cycle as it primarily ensures that the DNA has been accurately replicated and is free of damage before the cell proceeds to mitosis. This checkpoint occurs after the S phase, where DNA replication takes place, and allows the cell to assess if the DNA is intact and any necessary repairs can be made. If DNA damage is detected, the cell cycle can be halted, and repair mechanisms can be activated. This prevents cells with damaged DNA from dividing, which is vital for maintaining genetic stability and preventing issues such as cancer.

In contrast, the G1 checkpoint assesses cell size and DNA integrity before replication, the M checkpoint ensures proper chromosome alignment during mitosis, and the S checkpoint primarily focuses on the progress of DNA synthesis itself. Therefore, the G2 checkpoint is specifically designed to verify that the DNA is undamaged post-replication, making it the correct choice for this question.