$$20 \mathrm{\ nm} \leq \text{virus size} \leq 400 \mathrm{\ nm}$$

Question 1

Which of the following best describes why viruses are considered nonliving microbes?

Accepted Answer

They are acellular and obligate intracellular pathogens.

Question 2

A scientist discovers a new virus that infects only one species of bird. Which term best describes this virus’s host range?

Accepted Answer

Narrow tropism

Question 3

Which structural feature is found in all viruses and is responsible for protecting the viral genome?

Accepted Answer

Capsid

Question 4

What is the main difference between enveloped and naked viruses regarding their method of exiting the host cell?

Accepted Answer

Enveloped viruses bud off the host cell, while naked viruses lyse the host cell.

Question 5

Which of the following statements about bacteriophages is correct?

Accepted Answer

They always have a complex capsid structure.

Question 6

Influenza viruses frequently mutate and experience small changes in their spike proteins. What is the term for this phenomenon?

Accepted Answer

Antigenic drift

Question 7

Which viral spike proteins are critical for influenza A virus entry and immune recognition?

Accepted Answer

Hemagglutinin (HA) and Neuraminidase (NA)

Question 8

A virus with a helical capsid structure would most likely appear as:

Accepted Answer

A hollow tube

Question 9

Which property is used by the International Committee on Taxonomy of Viruses to classify viruses?

Accepted Answer

Type of nucleic acid (DNA or RNA)

Question 10

Why do RNA viruses tend to evolve faster than DNA viruses?

Accepted Answer

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

Question 11

Which of the following equations correctly represents the size range of most viruses?

Accepted Answer

$$20 \mathrm{\ nm} \leq 	ext{virus size} \leq 400 \mathrm{\ nm}$$

Question 12

A patient is infected with a virus that has a single-stranded negative-sense RNA genome. Which enzyme must this virus encode to replicate its genome?

Accepted Answer

RNA-dependent RNA polymerase

Question 13

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

Accepted Answer

It results in major genetic changes, potentially causing pandemics.

Question 14

Which of the following is NOT a convention used in viral taxonomy?

Accepted Answer

Domain

Question 15

A virus is described as having an icosahedral capsid. What does this mean?

Accepted Answer

Its capsid is a three-dimensional polygon with 20 faces.

Question 16

Which of the following statements about viral genomes is correct?

Accepted Answer

Viral genomes can be DNA or RNA, single- or double-stranded.

Question 17

A researcher is studying a virus that buds off the host cell, taking a portion of the cell membrane with it. What type of virus is this?

Accepted Answer

Enveloped virus

Question 18

Which of the following is a real-world consequence of antigenic shift in influenza viruses?

Accepted Answer

Expanded host range and potential for pandemics

Question 19

Which of the following best describes the role of capsomeres in viral structure?

Accepted Answer

They are protein subunits that make up the capsid.

Question 20

A virus is found to infect both humans and pigs. What does this indicate about its host range?

Accepted Answer

It has a broad tropism.

Viruses and Prions: Structure, Classification, and Key Features CHAPTER 6A

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