Radiobiology: oxygen effect: 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: oxygen effect

Sample item

Hypoxic tumour cells are more resistant to low-LET radiation than well-oxygenated cells because of which mechanism?

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

The answer and the reasoning

D. Oxygen fixes free-radical DNA damage, making it permanent

Oxygen reacts with radiation-induced free radicals on DNA to fix the damage, the oxygen effect. The oxygen enhancement ratio is about 2.5 to 3 for X-rays. High-LET radiation shows a lower OER.

Option by option

  • A. Oxygen absorbs the photons

    Oxygen does not absorb the photon energy in a relevant manner.

  • B. Hypoxia increases the cell division rate

    Hypoxia generally slows cell cycling.

  • C. Oxygen repairs DNA breaks

    Oxygen does not repair damage.

  • D. Oxygen fixes free-radical DNA damage, making it permanent (correct)

    Correct. Oxygen fixes radical damage and enhances killing.

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 D, Oxygen fixes free-radical DNA damage, making it permanent. Oxygen reacts with radiation-induced free radicals on DNA to fix the damage, the oxygen effect.

Why is "Oxygen absorbs the photons" not the answer?

Oxygen does not absorb the photon energy in a relevant manner.

Why is "Hypoxia increases the cell division rate" not the answer?

Hypoxia generally slows cell cycling.

Why is "Oxygen repairs DNA breaks" not the answer?

Oxygen does not repair damage.

What concept does this question test?

It tests Radiobiology: oxygen effect in Radiology. The oxygen enhancement ratio is about 2.5 to 3 for X-rays. High-LET radiation shows a lower OER.

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: oxygen effect?

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.