Molecular biology and genetics: Lynch syndrome: 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.

Try it

Biochemistry · Molecular biology and genetics: Lynch syndrome

Sample item

A 38-year-old has colon cancer. His mother had endometrial cancer and his uncle had colon cancer at 45. The tumour shows microsatellite instability. Which DNA repair pathway is defective?

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

The answer and the reasoning

D. Mismatch repair

Lynch syndrome is caused by germline defects in mismatch repair genes such as MLH1 and MSH2, so replication errors in repeat sequences go uncorrected and microsatellite instability results. Colorectal and endometrial cancers cluster in families. Excision repair defects cause xeroderma pigmentosum instead.

Option by option

  • A. Nucleotide excision repair

    Nucleotide excision repair defects cause xeroderma pigmentosum.

  • B. Base excision repair

    Base excision repair defects cause MUTYH-associated polyposis, a recessive polyposis.

  • C. Homologous recombination

    Homologous recombination defects are linked to BRCA-related breast and ovarian cancer.

  • D. Mismatch repair (correct)

    Correct. Mismatch repair failure produces microsatellite instability in this family cancer syndrome.

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, Mismatch repair. Lynch syndrome is caused by germline defects in mismatch repair genes such as MLH1 and MSH2, so replication errors in repeat sequences go uncorrected and microsatellite instability results.

Why is "Nucleotide excision repair" not the answer?

Nucleotide excision repair defects cause xeroderma pigmentosum.

Why is "Base excision repair" not the answer?

Base excision repair defects cause MUTYH-associated polyposis, a recessive polyposis.

Why is "Homologous recombination" not the answer?

Homologous recombination defects are linked to BRCA-related breast and ovarian cancer.

What concept does this question test?

It tests Molecular biology and genetics: Lynch syndrome in Biochemistry. Colorectal and endometrial cancers cluster in families. Excision repair defects cause xeroderma pigmentosum instead.

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 Molecular biology and genetics: Lynch syndrome?

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.