Question 1

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

Accepted Answer

A virus can infect only specific types of cells in one host, determined by specific attachment sites and cellular factors.

Question 2

Which of the following is NOT a characteristic of viruses?

Accepted Answer

They contain both DNA and RNA in the same virion.

Question 3

A scientist is growing bacteriophages in the laboratory. What is the most likely method for quantifying the number of viruses present?

Accepted Answer

Counting the number of plaques formed on a bacterial lawn, expressed as plaque-forming units (PFU).

Question 4

Which of the following best describes the structure of a helical virus?

Accepted Answer

A hollow, cylindrical capsid with the nucleic acid inside, as seen in the rabies and Ebola viruses.

Question 5

Which of the following is a correct match between a virus family and a disease it can cause?

Accepted Answer

Herpesviridae – Burkitt’s lymphoma

Question 6

During the lytic cycle of a T-even bacteriophage, what is the correct sequence of events?

Accepted Answer

Attachment, penetration, biosynthesis, maturation, release

Question 7

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

Accepted Answer

The virus is continuously released over a long period, often leading to fatal outcomes.

Question 8

Which laboratory method is commonly used to cultivate animal viruses for vaccine production?

Accepted Answer

Inoculation of embryonated eggs

Question 9

Which of the following best explains why viruses are not sensitive to antibiotics?

Accepted Answer

Viruses lack the metabolic pathways targeted by antibiotics, such as cell wall synthesis and protein synthesis machinery.

Question 10

A virus with a single-stranded RNA genome that serves directly as mRNA for protein synthesis is classified as:

Accepted Answer

A + (sense) strand RNA virus

Question 11

Which of the following is a unique feature of retroviruses?

Accepted Answer

They use reverse transcriptase to produce DNA from their RNA genome.

Question 12

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

Accepted Answer

A lysogenic phage transfers specific bacterial genes to another bacterium, altering the recipient’s genetic properties.

Question 13

Which of the following is a correct statement about prions?

Accepted Answer

They are infectious proteins that cause diseases such as Creutzfeldt-Jakob disease and mad cow disease.

Question 14

A patient presents with cold sores that recur during periods of stress. Which type of viral infection is this an example of?

Accepted Answer

Latent viral infection

Question 15

Which of the following best explains why plant viruses often require wounds or insect vectors to infect plant cells?

Accepted Answer

Plant cells have an impermeable cell wall that viruses cannot penetrate without assistance.

Question 16

Which of the following is a correct description of the Baltimore classification system for viruses?

Accepted Answer

It is based on the type of nucleic acid and how the virus produces its mRNA.

Question 17

A scientist observes a monolayer of animal cells in culture that shows visible deterioration after viral infection. What is this effect called?

Accepted Answer

Cytopathic effect (CPE)

Question 18

Which of the following is a possible outcome of lysogeny in bacteria?

Accepted Answer

The host cell exhibits new properties, such as toxin production, due to phage conversion.

Question 19

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

Accepted Answer

They are used for attachment to host cells and are composed of carbohydrate and protein.

Question 20

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

Accepted Answer

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

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

Study Guide - Practice Questions