Question 1

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

Accepted Answer

They require living host cells to multiply because they lack the necessary metabolic enzymes.

Question 2

A virus is found to have a single-stranded RNA genome and an envelope with spikes. Which of the following is a likely function of the spikes?

Accepted Answer

To facilitate attachment to specific host cell receptors.

Question 3

Which of the following best explains why most viruses have a narrow host range?

Accepted Answer

Viral attachment requires specific interactions with host cell receptors and cellular factors.

Question 4

Which of the following is TRUE regarding the genetic material of viruses?

Accepted Answer

Viral nucleic acid can be either single-stranded or double-stranded, but not both in the same virus.

Question 5

A scientist isolates a virus with an icosahedral capsid and no envelope. Which term best describes this virus's morphology?

Accepted Answer

Polyhedral

Question 6

Which of the following is a correct pairing of viral taxonomy?

Accepted Answer

Genus: simplexvirus

Question 7

During the lytic cycle of a T-even bacteriophage, what is the primary event occurring during the biosynthesis stage?

Accepted Answer

Viral nucleic acid and proteins are synthesized using host machinery.

Question 8

Which of the following is a unique feature of lysogeny in bacteriophage lambda?

Accepted Answer

The phage DNA integrates into the host genome as a prophage.

Question 9

A patient is diagnosed with diphtheria caused by Corynebacterium diphtheriae. The bacterium produces a toxin only when infected by a lysogenic phage. What is this phenomenon called?

Accepted Answer

Phage conversion

Question 10

Which of the following best describes the process of entry for an enveloped animal virus by fusion?

Accepted Answer

The viral envelope fuses with the host plasma membrane, releasing the capsid into the cytoplasm.

Question 11

Which of the following steps is unique to the replication of retroviruses such as HIV?

Accepted Answer

Synthesis of complementary DNA from an RNA template by reverse transcriptase.

Question 12

Which of the following is a key difference between latent and persistent viral infections?

Accepted Answer

Latent infections have periods with no detectable virus, while persistent infections involve continuous or intermittent viral production.

Question 13

Which of the following is TRUE regarding prion diseases?

Accepted Answer

They involve the conversion of normal host protein PrPc into the infectious form PrPsc.

Question 14

A plant pathologist discovers a new infectious agent causing disease in crops. It consists only of a short piece of naked RNA. What is this agent most likely to be?

Accepted Answer

A viroid

Question 15

Which of the following best explains why HIV is difficult to eliminate from the body?

Accepted Answer

HIV integrates its DNA into the host genome as a provirus, where it can remain latent and is protected from the immune system.

Question 16

Which of the following is a consequence of specialized transduction in bacteria?

Accepted Answer

Only genes adjacent to the prophage integration site are transferred to another bacterium.

Question 17

Which of the following is a correct sequence of events for the lytic cycle of a T-even bacteriophage?

Accepted Answer

Attachment → Penetration → Biosynthesis → Maturation → Release

Question 18

Which of the following best describes the process of budding in enveloped animal viruses?

Accepted Answer

The viral capsid acquires its envelope from the host cell plasma membrane during release, often without immediately killing the cell.

Question 19

Which of the following is a real-world example of a virus-induced cancer?

Accepted Answer

Cervical cancer caused by human papillomavirus (HPV)

Question 20

Which of the following equations best represents the process catalyzed by reverse transcriptase in retroviruses?

Accepted Answer

$$RNA \xrightarrow{	ext{reverse transcriptase}} DNA$$

Viruses, Viroids, and Prions: Structure, Classification, and Replication

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