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The Cell Cycle, Checkpoints and Apoptosis Quiz
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Which statement best describes G0 in human tissues?
- A It is a resting state outside the active cell cycle that is reversible in many cells but permanent in others You picked ✓
- B It is a brief interval between G2 and mitosis that cells enter when conditions are poor You picked ✕
- C It is the stage in which most cells duplicate their DNA before committing to division You picked ✕
- D It is a reversible arrest at the G1/S boundary caused by DNA damage checkpoints You picked ✕
- E It begins after anaphase in cells that have not yet completed cytokinesis You picked ✕
Correct!
Incorrect
The answer is A: It is a resting state outside the active cell cycle that is reversible in many cells but permanent in others
Explanation
Why A is correct
See The Cell Cycle Map. Option A is correct because G0 is a resting state, not a stage on the road to division. A proliferating cell moves through G1 (first gap, growth), S (DNA synthesis), G2 (second gap, preparation for mitosis) and M (mitosis and cytokinesis, the division itself). A cell in G0 has stepped out of this loop. Its cyclin-CDK activity (the kinase partnerships that drive each phase) is suppressed and its replication origins are not fired, so it is not preparing to divide. G0 is not a failed G1: many differentiated cells sit there for long periods yet can re-enter G1 when tissue demand returns, as hepatocytes (liver cells) do after substantial loss of liver tissue. Others are fully post-mitotic, meaning they have permanently left the cycle, as most mature neurons have. So the honest answer is that G0 is often reversible but not always. A simple picture is a car park: some cars wait there and drive off again, whereas a few are never moved.
- G0: a resting state outside the division cycle, not a stage leading to division.
- Reversible: many differentiated cells, such as hepatocytes, can re-enter G1 when needed.
- Permanent: some cells, such as most mature neurons, are post-mitotic and never return.
Why the other options are incorrect
- B. It is a brief interval between G2 and mitosis that cells enter when conditions are poor: G0 is a resting state outside the cell cycle, not a brief interval between G2 and mitosis; G2 leads directly into M phase. Your answer
- C. It is the stage in which most cells duplicate their DNA before committing to division: G0 is not where DNA is copied; S phase is the stage in which nuclear DNA is duplicated. Your answer
- D. It is a reversible arrest at the G1/S boundary caused by DNA damage checkpoints: G0 is not a DNA damage checkpoint arrest at the G1/S boundary; checkpoint arrest holds cells in the cycle, while G0 is a resting state outside it. Your answer
- E. It begins after anaphase in cells that have not yet completed cytokinesis: G0 is a resting state outside the cycle and does not begin in the middle of mitosis after anaphase; a cell may enter G0 after division, but the state is defined by withdrawal from the cycle. Your answer
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More questions from this set. Start the quiz to answer them and see each explanation.
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1
What must occur before the spindle assembly checkpoint permits anaphase?
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2
Cyclin B is bound to CDK1, but Wee1 activity remains high and Cdc25 is inactive. What follows?
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