Question 1

Which of the following statements best describes a key difference between viruses and prokaryotic cells?

Accepted Answer

Viruses lack cellular structure and cannot replicate without a host, whereas prokaryotic cells are living organisms capable of independent replication.

Question 2

A virus is composed of several main components. Which of the following correctly matches a viral component with its function?

Accepted Answer

Spikes: Facilitate attachment to specific host cell receptors.

Question 3

Antigenic shift and antigenic drift are important in the evolution of influenza viruses. Which statement best explains their impact?

Accepted Answer

Antigenic shift involves reassortment of genome segments, potentially causing new viral strains and outbreaks, while antigenic drift involves gradual mutations leading to seasonal epidemics.

Question 4

What is the significance of a virus's host range and tropism?

Accepted Answer

Host range defines which species a virus can infect, and tropism specifies which cells or tissues within the host are targeted.

Question 5

Which feature is characteristic of bacteriophage lytic replication?

Accepted Answer

Destruction of the host cell following the production and assembly of new phage particles.

Question 6

During bacteriophage lysogenic replication, which of the following occurs?

Accepted Answer

The phage genome integrates into the host chromosome and is replicated along with the host DNA.

Question 7

Which scenario best illustrates a lytic infection caused by an animal virus?

Accepted Answer

Influenza virus infecting respiratory cells, rapidly producing new virions and causing cell death.

Question 8

How do viruses contribute to evolution by spreading genes?

Accepted Answer

Viruses can transfer genetic material between organisms, driving evolution through gene innovation and selective pressure.

Question 9

Which process describes how bacteriophages can convert non-pathogenic bacteria into pathogens?

Accepted Answer

Bacteriophages transfer toxin genes to bacteria via transduction, enabling pathogenicity.

Question 10

Which method is commonly used to grow bacteriophages in the laboratory?

Accepted Answer

Infecting a bacterial lawn on an agar plate and observing plaque formation.

Question 11

What does a plaque assay measure in virology?

Accepted Answer

The concentration of viral particles capable of infecting and lysing host cells.

Question 12

Which of the following is an example of an antiviral drug and its mode of action?

Accepted Answer

Acyclovir: Inhibits viral DNA synthesis by acting as a nucleoside analog.

Question 13

A researcher observes that a virus can infect both human and avian cells. What does this suggest about the virus's host range?

Accepted Answer

The virus has a broad host range, capable of infecting multiple species.

Question 14

Which equation best represents the calculation of viral titer in a plaque assay?

Accepted Answer

$Viral\ titer = \frac{Number\ of\ plaques}{Dilution\ factor 	imes Volume\ plated}$

Question 15

Which of the following best explains why antigenic drift in influenza viruses leads to seasonal epidemics?

Accepted Answer

Antigenic drift results in gradual accumulation of mutations in viral surface proteins, allowing the virus to evade host immunity.

Question 16

Which statement accurately describes the difference between acute and latent viral infections?

Accepted Answer

Acute infections result in rapid onset of symptoms and viral replication, while latent infections involve periods of dormancy with possible reactivation.

Question 17

Which of the following is NOT a function of viral spikes?

Accepted Answer

Providing genetic material for viral replication.

Question 18

A scientist is studying a bacteriophage that integrates its genome into the host DNA and remains dormant. Which replication cycle is being observed?

Accepted Answer

Lysogenic cycle

Question 19

Which of the following best describes the role of selective pressure in viral evolution?

Accepted Answer

Selective pressure drives the emergence of viral variants that can evade host immunity.

Question 20

Which of the following is a plausible consequence of antigenic shift in influenza viruses?

Accepted Answer

Emergence of a novel viral strain capable of causing a pandemic.

Study Guide: Viruses and Bacteriophages in Microbiology

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