Virology: viral genome and 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.

Try it

Microbiology · Virology: viral genome and replication

Sample item

Purified genomic RNA from poliovirus produces progeny virus when introduced into susceptible cells, but purified genomic RNA from rabies virus does not. What explains the difference?

ARabies virus has a DNA genome that needs integrationBPoliovirus has an envelope that fuses with cellsCThe negative-sense rabies genome cannot be translated and needs virion-associated RNA polymeraseDThe rabies genome is segmented and incomplete

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

The answer and the reasoning

C. The negative-sense rabies genome cannot be translated and needs virion-associated RNA polymerase

Poliovirus has a positive-sense RNA genome that acts directly as mRNA, so naked RNA is infectious. Rabies virus has a non-segmented negative-sense genome that must first be transcribed into mRNA by an RNA-dependent RNA polymerase packaged inside the virion. Without the enzyme, the naked genome cannot start replication.

Option by option

A. Rabies virus has a DNA genome that needs integration
Rabies virus has an RNA genome and does not integrate.
B. Poliovirus has an envelope that fuses with cells
Poliovirus is non-enveloped, and its RNA works because it is positive-sense.
C. The negative-sense rabies genome cannot be translated and needs virion-associated RNA polymerase (correct)
Correct. Negative-strand viruses must carry their own transcriptase into the cell.
D. The rabies genome is segmented and incomplete
The rabies genome is non-segmented and complete.

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 negative-sense rabies genome cannot be translated and needs virion-associated RNA polymerase. Poliovirus has a positive-sense RNA genome that acts directly as mRNA, so naked RNA is infectious.

Why is "Rabies virus has a DNA genome that needs integration" not the answer?

Rabies virus has an RNA genome and does not integrate.

Why is "Poliovirus has an envelope that fuses with cells" not the answer?

Poliovirus is non-enveloped, and its RNA works because it is positive-sense.

Why is "The rabies genome is segmented and incomplete" not the answer?

The rabies genome is non-segmented and complete.

What concept does this question test?

It tests Virology: viral genome and replication in Microbiology. Rabies virus has a non-segmented negative-sense genome that must first be transcribed into mRNA by an RNA-dependent RNA polymerase packaged inside the virion. Without the enzyme, the naked genome cannot start replication.

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 Virology: viral genome and 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.