Advanced Placement (AP) Biology Practice Exam

What is the function of checkpoints in the cell cycle?

1. Facilitate cell division

2. Regulate progression through the cycle

3. Ensure chromosomal crossover

4. Maintain chromatin structure

The correct answer is: Regulate progression through the cycle

The function of checkpoints in the cell cycle is to regulate progression through the cycle. Checkpoints are critical control mechanisms that assess whether the cell is ready to proceed to the next phase of the cell cycle. They evaluate factors such as DNA integrity, cell size, and the replication status of DNA. For example, during the G1 checkpoint, the cell checks for DNA damage and ensures that the environment is favorable for DNA synthesis. If any issues are detected, the cell cycle can be halted to allow for repair or to direct the cell towards apoptosis if the damage is irreparable. Similarly, the G2 checkpoint checks whether DNA has been replicated correctly, and the M checkpoint ensures that chromosomes are properly aligned before separation during mitosis. By regulating these key transitions, checkpoints help maintain genomic stability and prevent the propagation of damaged or unprepared cells, which is vital for the health of the organism.