Final answer:
The ultimate function of checkpoints in the cell cycle is to halt the cell cycle when errors are detected, ensuring the cell is ready and error-free before advancing to the next phase.
Step-by-step explanation:
The ultimate function of checkpoints in the cell cycle is to ensure that the cell is ready to proceed before it moves on to the next phase of the cycle. Checkpoints serve as internal control mechanisms that halt the cell cycle when errors are detected, thus preserving the integrity of the cell's genetic material. This is crucial because mistakes in the duplication or distribution of the chromosomes can lead to mutations. Specifically, the G1 checkpoint ensures the cell is ready for DNA synthesis, the G2 checkpoint ensures all chromosomes have been replicated and that the replicated DNA is not damaged before mitosis, and the metaphase checkpoint, or spindle checkpoint, ensures that all sister chromatids are correctly attached to the spindle microtubules before proceeding to anaphase.