Radiobiology: cell cycle: practice question

A Radiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Radiology · Radiobiology: cell cycle

Sample item

In which phase of the cell cycle are cells most sensitive and least sensitive to radiation, respectively?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. G2/M most, late S least

Cells are most sensitive in G2 and M, and most resistant in late S phase when repair mechanisms by homologous recombination are active. This difference underlies the rationale for fractionation, which redistributes cells into sensitive phases. G1 shows intermediate sensitivity.

Option by option

  • A. G2/M most, late S least (correct)

    Correct. G2/M is most sensitive and late S is most resistant.

  • B. Late S most, G2/M least

    This reverses the relationship.

  • C. G1 most, M least

    M is among the most sensitive phases, not the least.

  • D. M most, G2 least

    G2 is highly sensitive, not resistant.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Radiology question

What is the answer to this Radiology question?

The best answer is A, G2/M most, late S least. Cells are most sensitive in G2 and M, and most resistant in late S phase when repair mechanisms by homologous recombination are active.

Why is "Late S most, G2/M least" not the answer?

This reverses the relationship.

Why is "G1 most, M least" not the answer?

M is among the most sensitive phases, not the least.

Why is "M most, G2 least" not the answer?

G2 is highly sensitive, not resistant.

What concept does this question test?

It tests Radiobiology: cell cycle in Radiology. This difference underlies the rationale for fractionation, which redistributes cells into sensitive phases. G1 shows intermediate sensitivity.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Radiobiology: cell cycle?

Learn signs with the image, and the disease they point to. Then use the flashcards and the other Radiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.