Virology: hepatitis B replication: practice question

A Microbiology 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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Microbiology · Virology: hepatitis B replication

Sample item

Hepatitis B virus has a DNA genome, yet lamivudine, a nucleoside reverse transcriptase inhibitor, suppresses its replication. What is the explanation?

AThe virus integrates as a provirus that is essential for each replication cycleBThe virus carries an RNA-dependent RNA polymerase in the virionCThe virus copies pregenomic RNA into DNA using its own reverse transcriptaseDThe virus uses a host RNA polymerase to copy DNA into DNA

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

The answer and the reasoning

C. The virus copies pregenomic RNA into DNA using its own reverse transcriptase

Hepadnaviruses replicate through an RNA intermediate. Host RNA polymerase II transcribes the covalently closed circular DNA to pregenomic RNA, which is reverse transcribed by the viral polymerase inside the nucleocapsid. Nucleoside analogues such as lamivudine, entecavir and tenofovir inhibit this reverse transcriptase step.

Option by option

A. The virus integrates as a provirus that is essential for each replication cycle
Integration occurs and contributes to hepatocellular carcinoma but is not required for replication.
B. The virus carries an RNA-dependent RNA polymerase in the virion
An RNA-dependent RNA polymerase would be inhibited by agents such as sofosbuvir and is not a feature of HBV.
C. The virus copies pregenomic RNA into DNA using its own reverse transcriptase (correct)
Reverse transcription of the pregenomic RNA is the step blocked by these drugs.
D. The virus uses a host RNA polymerase to copy DNA into DNA
Host RNA polymerase transcribes DNA into RNA, and DNA is not copied into DNA by it.

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.

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is C, The virus copies pregenomic RNA into DNA using its own reverse transcriptase. Hepadnaviruses replicate through an RNA intermediate.

Why is "The virus integrates as a provirus that is essential for each replica…" not the answer?

Integration occurs and contributes to hepatocellular carcinoma but is not required for replication.

Why is "The virus carries an RNA-dependent RNA polymerase in the virion" not the answer?

An RNA-dependent RNA polymerase would be inhibited by agents such as sofosbuvir and is not a feature of HBV.

Why is "The virus uses a host RNA polymerase to copy DNA into DNA" not the answer?

Host RNA polymerase transcribes DNA into RNA, and DNA is not copied into DNA by it.

What concept does this question test?

It tests Virology: hepatitis B replication in Microbiology. Host RNA polymerase II transcribes the covalently closed circular DNA to pregenomic RNA, which is reverse transcribed by the viral polymerase inside the nucleocapsid. Nucleoside analogues such as lamivudine, entecavir and tenofovir inhibit this reverse transcriptase step.

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 Virology: hepatitis B replication?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology 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.