Which statement best describes radiation-induced mitotic delay?

• A. Usually irreversible
• B. Generally lethal to undifferentiated cells
• C. Usually reversible
• D. Both A and C

Answer: (C)

Radiation-induced mitotic delay occurs when DNA damage activates the G2/M checkpoint, giving cells time to repair before entering mitosis. This arrest is typically temporary; once repair is completed, cells resume the cycle and proceed to mitosis. Because the purpose is to allow repair rather than to permanently block division, the delay is usually reversible. Only when damage is too severe or unrepaired do cells fail to recover, leading to cell death or permanent arrest. So the best description is that the delay is usually reversible. The idea that it is usually irreversible or inherently lethal to undifferentiated cells does not fit the common, transient checkpoint response.