Question 1

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

Accepted Answer

They can only replicate by hijacking the host cell's genetic and protein-synthesizing machinery.

Question 2

A scientist is studying a newly discovered infectious agent. It consists solely of a short, circular piece of single-stranded RNA with no protein coat. Which type of acellular pathogen is this most likely to be?

Accepted Answer

Viroid

Question 3

Which of the following statements about viral genomes is correct?

Accepted Answer

A virus can have either DNA or RNA as its genome, but never both at the same time.

Question 4

What is the main function of spike proteins found on the surface of many viruses?

Accepted Answer

They mediate attachment to specific host cell receptors, determining host range and tropism.

Question 5

Which of the following best describes the difference between antigenic drift and antigenic shift in influenza viruses?

Accepted Answer

Antigenic drift involves point mutations in spike proteins, while antigenic shift involves gene reassortment between different viral strains.

Question 6

A patient is diagnosed with a neurodegenerative disease caused by an infectious agent that contains no nucleic acid. Which of the following is the most likely cause?

Accepted Answer

Prion

Question 7

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

Accepted Answer

Adsorption → Penetration → Replication/Synthesis → Assembly → Maturation → Lysis & Release

Question 8

Which of the following is a key difference between the replication of most DNA viruses and most RNA viruses in animal cells?

Accepted Answer

Most DNA viruses replicate in the nucleus, while most RNA viruses replicate in the cytoplasm.

Question 9

A retrovirus infects a host cell. Which enzyme must it bring with it to ensure successful replication, and what is the function of this enzyme?

Accepted Answer

Reverse transcriptase, which synthesizes DNA from an RNA template: $$	ext{RNA} \xrightarrow{	ext{RT}} 	ext{DNA}$$

Question 10

Which of the following best describes a complex virus?

Accepted Answer

A virus with a polyhedral nucleocapsid and additional structures such as a helical tail and attachment fibers, e.g., bacteriophage.

Question 11

Which of the following is NOT a function of the viral capsid or envelope?

Accepted Answer

Synthesizing viral proteins inside the host cell.

Question 12

A virus is described as having a continuous helix of capsomers forming a cylindrical structure tightly associated with its nucleic acid. Which type of capsid does this virus have?

Accepted Answer

Helical capsid

Question 13

Which of the following best explains why classification of viruses is constantly changing and difficult?

Accepted Answer

Viruses mutate rapidly, leading to frequent changes in their genetic makeup and properties.

Question 14

Which of the following is a correct statement about viroids?

Accepted Answer

Viroids are short, circular pieces of ssRNA that do not code for any proteins and cause diseases in plants.

Question 15

A patient is infected with a virus that periodically reactivates after long periods of dormancy, causing symptoms to reappear. This type of infection is best described as:

Accepted Answer

Chronic latent infection

Question 16

Which of the following is an example of a virus causing cancer in humans?

Accepted Answer

Human papillomavirus (HPV) causing cervical cancer

Question 17

Which of the following best describes the process of lysogenic conversion?

Accepted Answer

A bacteriophage integrates its genome into the host chromosome, causing the host to express new traits such as toxin production.

Question 18

Which of the following best explains why prions are extremely difficult to destroy using standard sterilization techniques?

Accepted Answer

Prions are abnormally folded proteins that are highly resistant to heat, chemicals, and radiation.

Question 19

A laboratory is attempting to cultivate a newly discovered animal virus. Which of the following methods would be most appropriate for this purpose?

Accepted Answer

Inoculation of tissue (cell) cultures to observe cytopathic effects.

Question 20

Which of the following best describes the genome of a positive-sense single-stranded RNA (+ssRNA) virus?

Accepted Answer

The viral RNA can serve directly as mRNA for protein synthesis: $$	ext{+ssRNA} ightarrow 	ext{mRNA} ightarrow 	ext{Protein}$$

Chapter 6: Viruses and Acellular Pathogens – Structure, Classification, and History

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