Q: Which of the following equations correctly represents the calculation of viral titer in a plaque assay?

$$\text{Viral\ titer\ (PFU/ml)} = \frac{\text{Number\ of\ plaques}}{\text{Dilution\ factor} \times \text{Volume\ plated\ (ml)}}$$

Question 1

Which of the following best describes why RNA viruses mutate more rapidly than DNA viruses?

Accepted Answer

RNA polymerases lack proofreading capabilities, leading to higher mutation rates.

Question 2

A virus with a helical capsid, an envelope, and a segmented negative-sense RNA genome is most likely classified in which viral family?

Accepted Answer

Orthomyxoviridae

Question 3

Which step in the animal virus replication cycle is unique compared to bacteriophage replication?

Accepted Answer

Uncoating

Question 4

A patient is diagnosed with a persistent viral infection that periodically flares up with symptoms, followed by long periods of dormancy. Which virus is most likely responsible?

Accepted Answer

Herpes simplex virus (HSV)

Question 5

Which of the following best explains the process of antigenic shift in influenza viruses?

Accepted Answer

Reassortment of genome segments when two different strains coinfect a host cell

Question 6

Which laboratory method is most appropriate for quantifying the number of infectious bacteriophages in a sample?

Accepted Answer

Plaque assay

Question 7

A nucleoside analog antiviral drug is most likely to inhibit which step of the viral replication cycle?

Accepted Answer

Genome replication

Question 8

Which of the following is a distinguishing feature of prions compared to viruses?

Accepted Answer

Prions lack genetic material and are composed only of protein.

Question 9

Which of the following equations correctly represents the calculation of viral titer in a plaque assay?

Accepted Answer

$$	ext{Viral\ titer\ (PFU/ml)} = \frac{	ext{Number\ of\ plaques}}{	ext{Dilution\ factor} 	imes 	ext{Volume\ plated\ (ml)}}$$

Question 10

Which of the following best describes the role of viral spikes (peplomers)?

Accepted Answer

They mediate attachment to specific host cell receptors.

Question 11

A virus is described as having a single-stranded, positive-sense RNA genome. What is the first step after entry into the host cell?

Accepted Answer

Direct translation of the viral genome by host ribosomes

Question 12

Which of the following viruses is known to be oncogenic and associated with cervical cancer?

Accepted Answer

Human papillomavirus (HPV)

Question 13

Which of the following statements about the lysogenic cycle is correct?

Accepted Answer

The viral genome integrates into the host genome and is replicated along with it.

Question 14

Which diagnostic method is most sensitive for detecting low levels of viral genetic material in a clinical sample?

Accepted Answer

Polymerase chain reaction (PCR)

Question 15

Which of the following best explains why vaccines are effective in preventing viral infections?

Accepted Answer

They train the immune system to recognize and respond to viral antigens.

Question 16

A patient receives a postexposure prophylaxis injection after a potential rabies exposure. What is the mechanism of action for this treatment?

Accepted Answer

It provides laboratory-prepared antibodies that block viral attachment and entry.

Question 17

Which of the following is a medically important DNA virus family that can cause oral and genital herpes?

Accepted Answer

Herpesviridae

Question 18

Which of the following best describes the difference between enveloped and naked viruses in their release from host cells?

Accepted Answer

Enveloped viruses are released by budding, while naked viruses are released by cell lysis.

Question 19

Which of the following is NOT a way that Creutzfeldt-Jakob disease (CJD) can be transmitted?

Accepted Answer

Through mosquito bites

Viruses and Prions: Structure, Classification, Replication, and Clinical Aspects

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