Question 1

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

Accepted Answer

They require living host cells to multiply.

Question 2

A scientist is attempting to culture a newly discovered bacteriophage. Which method would be most appropriate for quantifying the number of infectious phage particles?

Accepted Answer

Counting plaques on a bacterial lawn and expressing results as plaque-forming units (PFU).

Question 3

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

Accepted Answer

Enveloped viruses have a lipid, protein, and carbohydrate coating surrounding the capsid.

Question 4

A virus with a single-stranded, negative-sense RNA genome must first perform which step before synthesizing viral proteins?

Accepted Answer

Transcribe a complementary positive-sense RNA strand to serve as mRNA.

Question 5

Which of the following best explains why antibiotics are ineffective against viruses?

Accepted Answer

Viruses lack a cell wall and metabolic pathways targeted by antibiotics.

Question 6

During the lysogenic cycle of bacteriophage lambda, what is the term for phage DNA that has integrated into the host chromosome?

Accepted Answer

Prophage

Question 7

Which of the following is a correct taxonomic designation for a viral family?

Accepted Answer

Herpesviridae

Question 8

A patient develops cold sores years after the initial infection. This is an example of which type of viral infection?

Accepted Answer

Latent infection

Question 9

Which of the following best describes the role of reverse transcriptase in the replication of Retroviridae viruses such as HIV?

Accepted Answer

It copies viral RNA to produce double-stranded DNA.

Question 10

Which of the following statements about prions is correct?

Accepted Answer

Prions are infectious proteins that can induce abnormal folding of normal cellular proteins.

Question 11

A virus is found to have a polyhedral capsid and no envelope. Which of the following is most likely true about this virus?

Accepted Answer

It is heat-resistant and lacks a lipid membrane.

Question 12

Which of the following best explains why a virus such as Hepatitis B is classified in the family Hepadnaviridae?

Accepted Answer

It contains double-stranded DNA, is enveloped, and uses reverse transcriptase.

Question 13

Which of the following laboratory techniques is most useful for identifying a virus based on its genetic material?

Accepted Answer

Polymerase chain reaction (PCR)

Question 14

A patient is diagnosed with a persistent viral infection. Which of the following best describes this type of infection?

Accepted Answer

The infection occurs gradually over a long period and is generally fatal.

Question 15

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

Accepted Answer

Attachment → Penetration → Biosynthesis → Maturation → Release

Question 16

Which of the following best describes the process of specialized transduction?

Accepted Answer

A lysogenic phage transfers specific bacterial genes adjacent to the prophage to another bacterium.

Question 17

Which of the following is a characteristic of viroids?

Accepted Answer

They are composed solely of a short strand of circular, single-stranded RNA with no protein coat.

Question 18

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

Accepted Answer

They are used for attachment to specific host cell receptors.

Question 19

A transformed cell resulting from viral oncogenesis is most likely to exhibit which of the following features?

Accepted Answer

A tumor-specific transplant antigen (TSTA) on the surface and a T antigen in the nucleus.

Question 20

Which of the following best describes the host range of a virus?

Accepted Answer

The spectrum of host cells a virus can infect, determined by specific attachment sites and cellular factors.

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

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