Final answer:
Checkpoints are critical junctures in the cell cycle that ensure favorable conditions for cell division by assessing DNA integrity, chromosome duplication, and kinetochore attachment to spindle fibers.
Step-by-step explanation:
Checkpoints are places in the cell cycle where proteins survey the cell to make sure that conditions for a favorable cell division have been met. There are three major checkpoints in the eukaryotic cell cycle. The first checkpoint occurs near the end of the G1 phase where the integrity of the DNA is assessed. The second checkpoint is at the G2/M transition, ensuring that proper chromosome duplication has occurred. The final, third checkpoint occurs during metaphase, where it is confirmed that each kinetochore is attached to a spindle fiber for accurate chromosome segregation.
Two types of regulatory molecules, cyclins and cyclin-dependent kinases (Cdks), play a key role in advancing the cell cycle through these checkpoints, while tumor suppressor proteins act as negative regulators that can halt the cell cycle if necessary. A failure to properly regulate these checkpoints can lead to uncontrolled cell division and cancer. Hence, these checkpoints are crucial for maintaining the cell's genetic integrity and successful division.