Question 1

Which of the following best describes why viruses are considered obligate intracellular parasites?

Accepted Answer

They require host cell machinery to synthesize progeny viruses.

Question 2

A bacteriophage infects a bacterial cell and causes the cell to lyse, releasing new phages. Which step in the viral life cycle does this represent?

Accepted Answer

Export of progeny viruses

Question 3

Which structural component is found in enveloped viruses but not in nonenveloped (naked) viruses?

Accepted Answer

Lipid membrane derived from the host cell

Question 4

The host range of a virus is primarily determined by:

Accepted Answer

The compatibility between viral and host cell-surface proteins

Question 5

Which of the following viruses is most likely to cause major economic losses in agriculture?

Accepted Answer

Tobacco Mosaic Virus

Question 6

A virus with a segmented (-) strand RNA genome, such as influenza, must bring which protein with it to initiate replication in the host cell?

Accepted Answer

Viral RNA-dependent RNA polymerase

Question 7

Why do new influenza vaccines need to be developed every year?

Accepted Answer

The virus mutates rapidly and undergoes genetic reassortment.

Question 8

Which of the following best explains why SARS-CoV-2 is more transmissible than benign coronaviruses?

Accepted Answer

Its spike protein binds ACE2 with higher affinity, requiring fewer particles to establish infection.

Question 9

Which enzyme is essential for the replication of a (+) strand RNA virus like SARS-CoV-2?

Accepted Answer

RNA-dependent RNA polymerase

Question 10

A patient is treated with Paxlovid, a protease inhibitor, soon after SARS-CoV-2 infection. What is the primary effect of this drug?

Accepted Answer

It inhibits cleavage of viral polyproteins, preventing formation of functional enzymes.

Question 11

Which of the following is a unique feature of retroviruses such as HIV compared to classic RNA viruses?

Accepted Answer

They integrate a DNA copy of their genome into the host genome using reverse transcriptase.

Question 12

Which of the following best describes a latent viral infection?

Accepted Answer

The virus remains dormant in the host and can reactivate later, as seen with varicella-zoster virus.

Question 13

Gene therapy using viruses as vectors can sometimes lead to cancer in patients. What is the most likely explanation for this adverse effect?

Accepted Answer

The viral vector integrates near proto-oncogenes, activating them.

Question 14

Which of the following best explains why viruses are effective tools for gene therapy?

Accepted Answer

They are efficient delivery systems for genetic material into host cells.

Question 15

Which of the following steps is NOT part of the general viral life cycle?

Accepted Answer

Synthesis of host cell wall components

Question 16

A virus with a single-stranded DNA genome must first do which of the following upon entering a host cell?

Accepted Answer

Synthesize a complementary DNA strand to form double-stranded DNA

Question 17

Which of the following best describes the role of the viral capsid?

Accepted Answer

It packages and protects the viral genome.

Question 18

Which of the following is a plausible reason why a virus might carry enzymes inside its capsid?

Accepted Answer

To initiate replication or transcription of its genome immediately upon entry

Question 19

Which of the following best explains why the 1918 H1N1 influenza pandemic was both highly transmissible and highly virulent?

Accepted Answer

It infected both the upper and lower respiratory tracts.

Question 20

Which of the following drugs would be most effective if administered soon after SARS-CoV-2 infection and why?

Accepted Answer

Paxlovid, because it inhibits the viral protease required for polyprotein processing.

Viruses: Structure, Life Cycle, and Medical Relevance

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