Which checkpoint in the cell cycle ensures that DNA has been replicated correctly?

• A. S checkpoint
• B. G2 checkpoint
• C. G1 checkpoint
• D. M checkpoint

Answer: (B)

Verified step by step guidance

1. Understand the cell cycle: The cell cycle consists of several phases, including G1, S, G2, and M phases. Each phase has specific checkpoints to ensure the cell is ready to proceed to the next stage.
2. Identify the role of each checkpoint: The G1 checkpoint checks for cell size, nutrients, and DNA damage. The S phase is where DNA replication occurs, but it does not have a specific checkpoint. The G2 checkpoint ensures that DNA replication in the S phase has been completed correctly and that the cell is ready to enter mitosis. The M checkpoint ensures that all chromosomes are properly aligned and attached to the spindle before anaphase.
3. Focus on the G2 checkpoint: The G2 checkpoint is crucial for verifying that DNA replication has been completed without errors. It checks for DNA damage and ensures all DNA is replicated before the cell enters mitosis.
4. Consider the options: The S checkpoint is not a standard term used for a specific checkpoint in the cell cycle. The G1 checkpoint occurs before DNA replication, and the M checkpoint occurs after DNA replication, focusing on chromosome alignment.
5. Conclude with the correct checkpoint: Based on the roles of each checkpoint, the G2 checkpoint is responsible for ensuring that DNA has been replicated correctly before the cell proceeds to mitosis.