Molecular biology: practice question

A Biochemistry 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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Biochemistry · Molecular biology

Sample item

Xeroderma pigmentosum is due to a defect in which DNA repair pathway?

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

The answer and the reasoning

D. Nucleotide excision repair

Nucleotide excision repair removes bulky lesions such as UV-induced thymine dimers. Defects cause extreme UV sensitivity and a very high risk of skin cancers. Mismatch repair defects cause Lynch syndrome and breast cancer genes act in homologous recombination.

Option by option

  • A. Base excision repair

    Base excision repair fixes small base damage such as deamination.

  • B. Homologous recombination

    Homologous recombination repairs double-strand breaks; BRCA genes act here.

  • C. Mismatch repair

    Mismatch repair defects cause hereditary non-polyposis colorectal cancer.

  • D. Nucleotide excision repair (correct)

    Correct. Without it, UV dimers persist and drive skin cancer.

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.

More Biochemistry questions

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is D, Nucleotide excision repair. Nucleotide excision repair removes bulky lesions such as UV-induced thymine dimers.

Why is "Base excision repair" not the answer?

Base excision repair fixes small base damage such as deamination.

Why is "Homologous recombination" not the answer?

Homologous recombination repairs double-strand breaks; BRCA genes act here.

Why is "Mismatch repair" not the answer?

Mismatch repair defects cause hereditary non-polyposis colorectal cancer.

What concept does this question test?

It tests Molecular biology in Biochemistry. Defects cause extreme UV sensitivity and a very high risk of skin cancers. Mismatch repair defects cause Lynch syndrome and breast cancer genes act in homologous recombination.

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 Molecular biology?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry 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.