Virology: hepatitis B virus structure: 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 virus structure

Sample item

Electron microscopy of serum from a hepatitis B carrier shows 22 nm spheres, filamentous forms and 42 nm double-shelled particles. Which particle is the complete, infectious virion that contains DNA and DNA polymerase?

ASoluble HBeAgBThe 22 nm spherical particleCThe 42 nm Dane particleDThe filamentous particle

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

The answer and the reasoning

C. The 42 nm Dane particle

The Dane particle is the intact hepatitis B virion, with an outer envelope of HBsAg surrounding the nucleocapsid with HBcAg, the partly double-stranded DNA genome and DNA polymerase. The 22 nm spheres and filaments are excess surface antigen with no genome. HBeAg is a soluble marker of replication and infectivity, not a particle.

Option by option

A. Soluble HBeAg
HBeAg is a secreted protein that marks high replication, not an infectious particle.
B. The 22 nm spherical particle
The 22 nm sphere is made of HBsAg alone and has no nucleic acid.
C. The 42 nm Dane particle (correct)
Correct. The Dane particle is the complete infectious virion.
D. The filamentous particle
Filamentous forms also consist of surface antigen without a genome.

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 42 nm Dane particle. The Dane particle is the intact hepatitis B virion, with an outer envelope of HBsAg surrounding the nucleocapsid with HBcAg, the partly double-stranded DNA genome and DNA polymerase.

Why is "Soluble HBeAg" not the answer?

HBeAg is a secreted protein that marks high replication, not an infectious particle.

Why is "The 22 nm spherical particle" not the answer?

The 22 nm sphere is made of HBsAg alone and has no nucleic acid.

Why is "The filamentous particle" not the answer?

Filamentous forms also consist of surface antigen without a genome.

What concept does this question test?

It tests Virology: hepatitis B virus structure in Microbiology. The 22 nm spheres and filaments are excess surface antigen with no genome. HBeAg is a soluble marker of replication and infectivity, not a particle.

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 virus structure?

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.