Which of the following statements about the GO (G zero phase) phase of the cell cycle is most accurate?
Show answer & explanation
Correct answer: C
Explanation
Answer: It is a temporary quiescent stage where cells exit the cell cycle.
Explanation:
The G_0 phase is often referred to as the quiescent (inactive) stage. When a cell does not need to divide immediately, it 'exits' the active cell cycle after the G_1 phase and enters G_0.
Metabolic Activity: Even though the cell is not dividing, it remains metabolically active. It performs its specific functions (e.g., a nerve cell sending signals) but does not replicate its DNA.
Reversibility: For many cells, this is a temporary state. If the body needs more cells (due to injury or growth signals), cells can be 'called back' from G_0 to re-enter the G_1 phase and start dividing again.
Additional Key Points:
Permanent G_0: Some cells, like neurons (nerve cells) and heart muscle cells, enter G_0 permanently and rarely, if ever, divide again in an adult.
Checkpoints: The decision to enter G_0 usually happens at the G_1 checkpoint (Restriction Point).
Contrast with Cancer: Cancerous cells usually bypass the $G_0$ phase or ignore the signals to stay in it, leading to uncontrolled, rapid division.
Potential Q&A:
Q: Does DNA replication occur in the G_0 phase?
A: No. DNA replication occurs only in the S phase (Synthesis phase) of the cell cycle.
Q: Are cells in G_0 dead?
A: No. They are fully functional and metabolically active; they are simply not preparing for division.