Molecular biology and genetics: chromatin states: 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 and genetics: chromatin states

Sample item

Which pattern characterises transcriptionally silent heterochromatin?

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

The answer and the reasoning

C. Hypoacetylated histones with methylated DNA

Silent chromatin has deacetylated histone tails, methylation of lysine residues such as H3K9, and methylated CpG islands, which compact the fibre. Acetylation neutralises lysine charge and loosens chromatin for transcription. Nucleosome-free promoters belong to active genes.

Option by option

  • A. Nucleosome-free promoter regions

    Open nucleosome-free promoters belong to active genes.

  • B. Hyperacetylated histones with unmethylated DNA

    Hyperacetylation and unmethylated DNA mark active chromatin.

  • C. Hypoacetylated histones with methylated DNA (correct)

    Correct. Deacetylated histones and CpG methylation condense chromatin and silence genes.

  • D. Histone octamers replaced by sigma factor

    Sigma factor is a bacterial transcription initiation protein and does not replace histones.

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 C, Hypoacetylated histones with methylated DNA. Silent chromatin has deacetylated histone tails, methylation of lysine residues such as H3K9, and methylated CpG islands, which compact the fibre.

Why is "Nucleosome-free promoter regions" not the answer?

Open nucleosome-free promoters belong to active genes.

Why is "Hyperacetylated histones with unmethylated DNA" not the answer?

Hyperacetylation and unmethylated DNA mark active chromatin.

Why is "Histone octamers replaced by sigma factor" not the answer?

Sigma factor is a bacterial transcription initiation protein and does not replace histones.

What concept does this question test?

It tests Molecular biology and genetics: chromatin states in Biochemistry. Acetylation neutralises lysine charge and loosens chromatin for transcription. Nucleosome-free promoters belong to active genes.

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 and genetics: chromatin states?

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.