Question 1

Which of the following best explains why viruses are considered obligate intracellular pathogens?

Accepted Answer

They require host cell machinery to replicate their genome and produce new virions.

Question 2

A scientist discovers a new virus with a helical capsid, an envelope, and a segmented RNA genome. Which of the following statements about this virus is most likely true?

Accepted Answer

It can undergo antigenic shift if it co-infects a host cell with another related virus.

Question 3

Which of the following best describes the function of viral spikes?

Accepted Answer

They are glycoprotein extensions that help viruses attach and gain entry to host cells.

Question 4

Which of the following is a key difference between the lytic and lysogenic replication cycles of bacteriophages?

Accepted Answer

In the lysogenic cycle, the phage genome integrates into the host genome and can remain dormant.

Question 5

A patient receives an influenza vaccine, but months later contracts the flu. Which process most likely explains the vaccine's failure?

Accepted Answer

Antigenic drift, which causes minor changes in viral spike proteins due to frequent mutations.

Question 6

Which of the following best describes a persistent viral infection?

Accepted Answer

The virus is not cleared from the host and remains in the body, sometimes with periods of dormancy or continuous low-level replication.

Question 7

Which of the following is an example of a latent viral infection?

Accepted Answer

Varicella-zoster virus (chickenpox and shingles)

Question 8

Which of the following is a correct sequence of steps in the generalized animal virus replication cycle?

Accepted Answer

Attachment → Penetration → Uncoating → Replication → Assembly → Release

Question 9

Which of the following best explains why RNA viruses tend to mutate more rapidly than DNA viruses?

Accepted Answer

RNA polymerases lack proofreading capabilities, leading to more errors during replication.

Question 10

A virus is classified as oncogenic if it:

Accepted Answer

Stimulates uncontrolled host cell division and/or decreases host cell responsiveness to death signals.

Question 11

Which of the following is a real-world example of phage conversion, where a bacteriophage confers new pathogenic properties to a bacterium?

Accepted Answer

Corynebacterium diphtheriae acquiring the ability to produce diphtheria toxin.

Question 12

Which of the following is NOT a typical target for antiviral drugs?

Accepted Answer

Bacterial cell wall synthesis

Question 13

Which of the following statements about prions is correct?

Accepted Answer

They are infectious proteins that cause transmissible spongiform encephalopathies.

Question 14

Which of the following best explains why developing antiviral drugs is more challenging than developing antibacterial drugs?

Accepted Answer

Viruses use host cell machinery for replication, so there are fewer unique viral targets for drugs.

Question 15

Which of the following equations best represents the exponential increase in the number of virions produced during a lytic infection, assuming each infected cell releases $n$ new virions and $k$ cycles occur?

Accepted Answer

$N = n^k$

Question 16

A patient is diagnosed with a chronic viral infection. Which of the following best describes the likely course of this infection?

Accepted Answer

The virus replicates at low levels for a long period, and symptoms may persist or progress slowly.

Question 17

Which of the following best describes antigenic shift in influenza viruses?

Accepted Answer

A major genetic reassortment that can result in new viral strains with increased infectivity or expanded host range.

Question 18

Which of the following is a key structural difference between enveloped and naked animal viruses?

Accepted Answer

Enveloped viruses have a lipid-based envelope derived from the host cell membrane, while naked viruses do not.

Question 19

Which of the following is a disease caused by prions in humans?

Accepted Answer

Creutzfeldt-Jakob disease

Question 20

Which of the following best explains why vaccination is an effective means to limit viral infection?

Accepted Answer

Vaccines train the immune system to recognize viral antigens, enabling a faster and stronger response upon exposure.

Viruses and Prions: Structure, Replication, and Pathogenicity

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