Final answer:
There are three checkpoints in cellular division: one near the end of G1, one at the G2-M transition, and one during metaphase. These checkpoints ensure the cell's readiness and the integrity of its genetic material before proceeding to the next phase.
Step-by-step explanation:
In cellular division, there are three checkpoints that ensure the cell is ready to proceed to the next phase of the cycle. These checkpoints are critical control mechanisms that help maintain the integrity of the cell's genetic material during division. The three main cell-cycle checkpoints are:
- The first checkpoint occurs near the end of the G1 phase, where the cell evaluates whether it has the necessary resources and is in a favorable environment to embark on the path of cell division.
- The second checkpoint is at the G2-M transition, which ensures that all DNA has been replicated correctly and that the cell is prepared for mitosis.
- The third checkpoint happens during metaphase, known as the M checkpoint, where the cell checks to make sure all the chromosomes are properly attached to the spindle apparatus before anaphase begins.
If any of the checkpoints are not successfully passed, the cell cycle is halted to prevent the proliferation of cells with damaged DNA or other cellular abnormalities.