High School Biology : Cell Biology

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #3 : Understanding Cell Cycle Regulation

There are several checkpoints during the cell cycle to ensure proper growth and division. Which checkpoint of the cell cycle is considered the "point of no return?"

Possible Answers:

G2 checkpoint

G1 checkpoint

There is no point of no return. The cell can always go back and resume normal cell function. 

Metaphase checkpoint

Telophase checkpoint

Correct answer:

G1 checkpoint

Explanation:

Once the cell passes the G1 checkpoint, the cell becomes committed to the cell cycle and enters the S phase where DNA is replicated. The checkpoint is to ensure the cell has grown enough and has enough resources to begin DNA replication. The next checkpoint is the G2 checkpoint, where the cell checks and makes sure the DNA replicated correctly before beginning mitosis. If the cell does not pass this checkpoint, it commences apoptosis and dies. 

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