Question 1

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

Accepted Answer

Bacteria possess metabolic enzymes and can reproduce independently, while viruses lack metabolic enzymes and require a host cell for replication.

Question 2

Which viral morphology is correctly matched with its example?

Accepted Answer

Helical – Tobacco mosaic virus

Question 3

A scientist is attempting to cultivate a newly discovered virus. Which method would be most appropriate if the virus only infects humans and cannot be grown in standard cell culture?

Accepted Answer

Inoculation into embryonated eggs

Question 4

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

Accepted Answer

The phage attaches, injects its DNA, replicates, assembles new phages, and lyses the host cell to release progeny.

Question 5

Which of the following is a cytopathic effect commonly observed in cells infected by certain viruses?

Accepted Answer

Formation of inclusion bodies such as Negri bodies in rabies infection

Question 6

A patient’s serum is tested for antibodies against a specific virus using a neutralization test. What is the principle behind this test?

Accepted Answer

Antibodies block the virus, preventing it from infecting cells, indicating prior exposure.

Question 7

Which of the following best explains why antiviral drugs that inhibit viral multiplication are often toxic to host cells?

Accepted Answer

Viruses rely on host cell machinery for replication, so drugs targeting viral processes also affect host cells.

Question 8

Which of the following is a unique feature of prions compared to viruses?

Accepted Answer

Prions are proteinaceous infectious particles with no nucleic acid.

Question 9

A virus is described as having an icosahedral capsid and no envelope. Which term best describes its morphology?

Accepted Answer

Polyhedral

Question 10

Which of the following is a real-world example of lysogenic conversion, where a prophage confers new properties to a bacterial host?

Accepted Answer

E. coli O157:H7 producing Shiga toxin

Question 11

Which step in animal virus replication is NOT present in bacteriophage replication?

Accepted Answer

Entry by pinocytosis or membrane fusion

Question 12

A patient develops shingles years after recovering from chickenpox. This is an example of which type of viral infection?

Accepted Answer

Latent infection

Question 13

Which of the following best describes the role of spikes on the surface of enveloped viruses?

Accepted Answer

They facilitate attachment to host cell receptors and may contribute to virulence.

Question 14

Which laboratory method is most commonly used for the identification of viruses in clinical samples?

Accepted Answer

Serological tests such as ELISA

Question 15

Which of the following equations best represents the exponential increase in the number of virions during the lytic cycle?

Accepted Answer

$$N = N_0$ e$$^{kt}$$

Question 16

Which of the following is a reason why prion diseases are particularly concerning in medical settings?

Accepted Answer

Prions can be transmitted by contaminated surgical instruments and are resistant to standard sterilization.

Question 17

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

Accepted Answer

They require host cell machinery for replication and cannot carry out metabolic processes independently.

Question 18

Which of the following is a potential outcome of lysogeny in bacteria?

Accepted Answer

Acquisition of new genetic traits, such as toxin production

Question 19

Which of the following best describes the process of viral budding?

Accepted Answer

The virus acquires its envelope from the host cell membrane as it exits the cell.

Question 20

Which of the following is a real-world example of a prion disease in humans?

Accepted Answer

Variant Creutzfeldt-Jakob disease

Ch 13 Viruses, Viroids, and Prions: Structure, Multiplication, and Pathogenicity

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