Question 1

Which of the following best differentiates a virus from a bacterium?

Accepted Answer

Viruses lack both ribosomes and metabolic machinery, while bacteria possess both.

Question 2

Which structural feature is unique to enveloped viruses compared to nonenveloped viruses?

Accepted Answer

A lipid bilayer derived from the host cell membrane.

Question 3

A viral species is best defined as:

Accepted Answer

A group of viruses sharing the same genetic information and ecological niche.

Question 4

Which of the following correctly matches a virus family, genus, and common name?

Accepted Answer

Family: Herpesviridae; Genus: Simplexvirus; Common name: Herpes simplex virus

Question 5

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

Accepted Answer

The double-layer agar (plaque) method

Question 6

Which of the following is NOT a typical method for culturing animal viruses?

Accepted Answer

Growing on nutrient agar plates

Question 7

Which of the following is NOT a technique used to identify viruses?

Accepted Answer

Gram staining

Question 8

During the lytic cycle of T-even bacteriophages, which step immediately follows penetration?

Accepted Answer

Biosynthesis of viral components

Question 9

In the lysogenic cycle of bacteriophage Lambda, what is the fate of the phage DNA after entry into the host cell?

Accepted Answer

It integrates into the host genome as a prophage.

Question 10

Which of the following best describes a key difference between the multiplication cycles of DNA- and RNA-containing animal viruses?

Accepted Answer

RNA viruses often replicate their genomes in the cytoplasm, while DNA viruses typically replicate in the nucleus.

Question 11

Which of the following best defines an oncogene?

Accepted Answer

A gene that can cause a normal cell to become cancerous when activated.

Question 12

How can both DNA- and RNA-containing viruses contribute to the development of cancer in humans?

Accepted Answer

By integrating their genetic material into host DNA and disrupting normal cell cycle regulation.

Question 13

Which of the following is an example of a latent viral infection?

Accepted Answer

Herpes simplex virus remaining dormant in nerve cells

Question 14

Which statement best differentiates between latent and persistent viral infections?

Accepted Answer

Latent infections involve periods of dormancy with no virus production, while persistent infections involve continuous low-level virus production.

Question 15

Which of the following correctly differentiates a virus, a viroid, and a prion?

Accepted Answer

A virus contains nucleic acid and a protein coat; a viroid is a naked RNA molecule; a prion is an infectious protein.

Question 16

Which step is unique to the lytic cycle of a plant virus compared to animal viruses?

Accepted Answer

Entry often requires mechanical damage to the plant cell wall.

Question 17

How can a protein, such as a prion, be infectious without containing nucleic acids?

Accepted Answer

By inducing misfolding of normal host proteins into the abnormal prion form.

Question 18

A researcher is studying a virus that can remain dormant in host cells for years and then suddenly reactivate, causing symptoms. Which type of infection is this, and which virus is a classic example?

Accepted Answer

Latent infection; Herpes simplex virus

Question 19

A patient is diagnosed with a cancer linked to a viral infection. Which of the following mechanisms most likely contributed to the cancer development?

Accepted Answer

Viral integration disrupted a tumor suppressor gene in the host DNA.

Question 20

Which of the following equations best represents the burst size ($$B) in a $$lytic bacteriophage infection, where $$N_{final} is $$the number of phage particles released and $$N_{infected} is $$the number of infected bacterial cells?

Accepted Answer

$$B = \frac{N_{final}}{N_{infected}}$$

Microbiology: Viruses, Viral Structure, and Viral Life Cycles – Guided Study

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