Radiobiology — NDEB AFK MCQ

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ModerateBiomedical SciencesRadiobiologyNDEB AFK

Which phase of the cell cycle is most sensitive to ionizing radiation?

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Correct answer: B — M phase (mitosis)

Cells in M phase (mitosis) are most radiosensitive because chromosomes are condensed and maximally vulnerable to DNA damage. G2 is the second most sensitive phase. Cells in late S phase are most radioresistant due to DNA repair mechanisms being active during replication. This principle underlies radiation therapy fractionation schedules.

Reference: White & Pharoah – Oral Radiology: Principles and Interpretation, 8th ed., 2019