Question 1

Which of the following statements best distinguishes viruses from typical bacteria?

Accepted Answer

Viruses lack ATP-generating mechanisms and ribosomes.

Question 2

A scientist is studying a pathogen that passes through bacteriological filters, lacks a plasma membrane, and does not perform binary fission. Which of the following is the most likely identity of this pathogen?

Accepted Answer

Virus

Question 3

Which of the following best explains why most viruses infect only specific types of cells in one host?

Accepted Answer

Viruses require specific host attachment sites and compatible cellular factors.

Question 4

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

Accepted Answer

Poxviridae – smallpox

Question 5

A patient presents with cold sores that recur during periods of stress. Which type of viral infection does this represent, and what is the likely virus involved?

Accepted Answer

Latent infection; Herpes Simplex Virus (HSV)

Question 6

Which of the following best describes the lytic cycle of a bacteriophage?

Accepted Answer

The phage causes lysis and death of the host cell after producing new phages.

Question 7

Which of the following steps is unique to the multiplication of animal viruses compared to bacteriophages?

Accepted Answer

Entry by receptor-mediated endocytosis or fusion

Question 8

A virologist is culturing animal viruses in the laboratory. Which of the following methods would NOT be appropriate for this purpose?

Accepted Answer

Culturing viruses in bacterial agar plates

Question 9

Which of the following is a characteristic of viroids that distinguishes them from viruses?

Accepted Answer

Viroids are composed solely of a short strand of circular, single-stranded RNA.

Question 10

Which of the following best describes the role of reverse transcriptase in the replication of certain viruses?

Accepted Answer

It produces DNA from an RNA template.

Question 11

A patient is diagnosed with a persistent viral infection that gradually worsens over years and is ultimately fatal. Which of the following is the most likely example of such an infection?

Accepted Answer

Subacute sclerosing panencephalitis caused by measles virus

Question 12

Which of the following best describes a prion?

Accepted Answer

A proteinaceous infectious particle that lacks nucleic acids

Question 13

Which of the following is a correct sequence of events in the lytic cycle of a T-even bacteriophage?

Accepted Answer

Attachment → Penetration → Biosynthesis → Maturation → Release

Question 14

Which of the following is a function of the viral envelope?

Accepted Answer

It helps the virus attach to host cells via embedded spikes.

Question 15

Which of the following best explains why antibiotics are ineffective against viruses?

Accepted Answer

Viruses lack the metabolic pathways targeted by antibiotics.

Question 16

A laboratory is using PCR (polymerase chain reaction) to identify a viral infection. What is the principle behind this technique?

Accepted Answer

Amplification of specific viral nucleic acid sequences

Question 17

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

Accepted Answer

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

Question 18

Which of the following is a correct match between a viral genus and its family?

Accepted Answer

Simplexvirus – Herpesviridae

Question 19

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

Accepted Answer

Transfer of specific bacterial genes adjacent to the prophage during lysogenic cycle

Question 20

Which of the following is a key difference between latent and persistent viral infections?

Accepted Answer

Latent infections remain dormant and can reactivate, while persistent infections involve continuous viral production.

Viruses, Viroids, and Prions: Structure, Classification, and Comparison with Bacteria

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