Radiation safety and radiobiology: ATM and radiosensitivity: 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 · Radiation safety and radiobiology: ATM and radiosensitivity

Sample item

A child with cerebellar ataxia and conjunctival telangiectasia develops severe toxicity after a standard dose of radiotherapy. What is the cellular defect?

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

The answer and the reasoning

B. Impaired detection and repair of DNA double-strand breaks (ATM)

Ataxia-telangiectasia is caused by mutation of the ATM gene, which signals DNA double-strand breaks. Cells cannot repair radiation damage properly, so patients are markedly radiosensitive and unnecessary diagnostic radiation is avoided.

Option by option

  • A. Absent nucleotide excision repair

    Failure of nucleotide excision repair underlies xeroderma pigmentosum and sensitivity to ultraviolet light.

  • B. Impaired detection and repair of DNA double-strand breaks (ATM) (correct)

    Correct. ATM is needed to respond to and repair double-strand breaks.

  • C. Defective mismatch repair

    Defective mismatch repair underlies Lynch syndrome and is not linked to radiosensitivity.

  • D. Excess of intracellular glutathione

    Excess glutathione scavenges free radicals and would make cells more 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 B, Impaired detection and repair of DNA double-strand breaks (ATM). Ataxia-telangiectasia is caused by mutation of the ATM gene, which signals DNA double-strand breaks.

Why is "Absent nucleotide excision repair" not the answer?

Failure of nucleotide excision repair underlies xeroderma pigmentosum and sensitivity to ultraviolet light.

Why is "Defective mismatch repair" not the answer?

Defective mismatch repair underlies Lynch syndrome and is not linked to radiosensitivity.

Why is "Excess of intracellular glutathione" not the answer?

Excess glutathione scavenges free radicals and would make cells more resistant.

What concept does this question test?

It tests Radiation safety and radiobiology: ATM and radiosensitivity in Radiology. Cells cannot repair radiation damage properly, so patients are markedly radiosensitive and unnecessary diagnostic radiation is avoided.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Radiation safety and radiobiology: ATM and radiosensitivity?

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.