Genetics: anticipation: 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 · Genetics: anticipation

Sample item

What genetic mechanism underlies anticipation in Huntington disease?

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

The answer and the reasoning

D. Expansion of CAG trinucleotide repeats

Huntington disease results from CAG repeat expansion in the HTT gene, and repeat length can increase across generations, causing earlier and more severe disease. Paternal transmission often shows greater expansion.

Option by option

  • A. Robertsonian translocation

    Robertsonian translocations involve acrocentric chromosomes.

  • B. Loss of an entire chromosome

    Whole-chromosome loss causes aneuploidy, not repeat anticipation.

  • C. Mitochondrial heteroplasmy only

    Mitochondrial heteroplasmy causes variable maternal inheritance.

  • D. Expansion of CAG trinucleotide repeats (correct)

    Correct. CAG expansion explains anticipation in Huntington disease.

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 Biochemistry question

What is the answer to this Biochemistry question?

The best answer is D, Expansion of CAG trinucleotide repeats. Huntington disease results from CAG repeat expansion in the HTT gene, and repeat length can increase across generations, causing earlier and more severe disease.

Why is "Robertsonian translocation" not the answer?

Robertsonian translocations involve acrocentric chromosomes.

Why is "Loss of an entire chromosome" not the answer?

Whole-chromosome loss causes aneuploidy, not repeat anticipation.

Why is "Mitochondrial heteroplasmy only" not the answer?

Mitochondrial heteroplasmy causes variable maternal inheritance.

What concept does this question test?

It tests Genetics: anticipation in Biochemistry. Paternal transmission often shows greater expansion.

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 Genetics: anticipation?

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.