Q: Which of the following equations correctly represents the calculation of plaque-forming units (PFU) in a viral plaque assay?

$$\text{PFU} = \frac{\text{Number of plaques}}{\text{Volume plated (mL)}}$$

Question 1

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

Accepted Answer

They require living host cells to multiply because they lack ribosomes and an ATP-generating mechanism.

Question 2

A scientist is attempting to culture a virus that infects humans. Which method would be LEAST effective for growing this virus?

Accepted Answer

Cultivation on nutrient agar without any living cells.

Question 3

Which feature distinguishes enveloped viruses from naked capsid viruses in terms of their release from host cells?

Accepted Answer

Enveloped viruses are released by budding, while naked capsid viruses are released by cell rupture.

Question 4

A virus has a genome consisting of single-stranded RNA, and it uses reverse transcriptase to produce DNA from its RNA genome. According to the Baltimore classification, which group does this virus belong to?

Accepted Answer

Group VI: ssRNA viruses that produce DNA

Question 5

During the lytic cycle of a T-even bacteriophage, which step involves the contraction of the tail sheath and injection of viral DNA into the host cell?

Accepted Answer

Penetration

Question 6

Which of the following is a consequence of lysogeny in bacteria infected by lambdavirus?

Accepted Answer

The host cell becomes immune to reinfection by the same phage.

Question 7

A patient is suspected of having influenza. Which laboratory technique would be most appropriate for identifying the virus?

Accepted Answer

ELISA to detect viral antigens.

Question 8

Which of the following viruses is associated with the development of cervical cancer in humans?

Accepted Answer

Alphapapillomavirus (HPV)

Question 9

What is the primary difference between latent and persistent viral infections?

Accepted Answer

Latent infections remain asymptomatic for long periods, while persistent infections involve gradual, continuous release of viruses.

Question 10

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

Accepted Answer

They are projections from the outer surface used for attachment to host cells.

Question 11

A virus is found to have a hollow, cylindrical capsid that is helical in shape. Which virus morphology does this describe?

Accepted Answer

Helical

Question 12

Which of the following equations correctly represents the calculation of plaque-forming units (PFU) in a viral plaque assay?

Accepted Answer

$$	ext{PFU} = \frac{	ext{Number of plaques}}{	ext{Volume plated (mL)}}$$

Question 13

Which viral family includes viruses that use reverse transcriptase to produce DNA from RNA and are associated with AIDS?

Accepted Answer

Retroviridae

Question 14

Which of the following is a proteinaceous infectious particle that can cause spongiform encephalopathies?

Accepted Answer

Prion

Question 15

A virus with a double-stranded DNA genome, an envelope, and the ability to cause skin lesions is most likely a member of which viral family?

Accepted Answer

Poxviridae

Question 16

Which step in the multiplication of animal viruses involves separating the viral nucleic acid from its capsid?

Accepted Answer

Uncoating

Question 17

Which of the following viruses is capable of latency and may reactivate to cause shingles?

Accepted Answer

Varicellovirus (Herpesvirus)

Question 18

Which of the following best explains how an RNA virus can cause cancer if it does not have DNA to insert into the host genome?

Accepted Answer

It uses reverse transcriptase to produce DNA from its RNA genome, which then integrates into the host DNA.

Question 19

Which of the following is NOT a typical outcome of lysogeny in bacteria?

Accepted Answer

Immediate lysis of the host cell.

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

Study Guide - Practice Questions

Study Guide - Flashcards