Question 1

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

Accepted Answer

Viruses require living host cells to multiply, whereas bacteria can reproduce independently.

Question 2

A scientist is studying a virus with a polyhedral capsid, no envelope, and spikes on its surface. Which of the following best describes this virus?

Accepted Answer

It is a non-enveloped, polyhedral virus with glycoprotein spikes.

Question 3

Which of the following is the correct order of events in the lytic cycle of a bacteriophage?

Accepted Answer

Attachment, penetration, synthesis, maturation, release

Question 4

A patient is diagnosed with a persistent viral infection that remains dormant for years before reactivating. Which type of infection is this, and which virus is a classic example?

Accepted Answer

Latent infection; Herpes Simplex Virus

Question 5

Which of the following best explains how a protein can be infectious, as seen in prion diseases?

Accepted Answer

The protein acts as a template, causing normal proteins to misfold into the infectious form.

Question 6

Which of the following is a key difference between antigenic shift and antigenic drift in influenza viruses?

Accepted Answer

Antigenic shift involves major genetic reassortment, while antigenic drift involves minor mutations.

Question 7

A researcher is using the plaque method to quantify bacteriophages. What does each plaque represent?

Accepted Answer

A single virus that has lysed a bacterial cell and its descendants

Question 8

Which of the following best describes the role of a provirus in animal cells?

Accepted Answer

A provirus is viral DNA integrated into the host genome, remaining latent and potentially reactivating.

Question 9

Which of the following is a correct match between a virus family, genus, and common name?

Accepted Answer

Family: Herpesviridae; Genus: Simplexvirus; Common name: Herpes Simplex Virus

Question 10

A bacterium produces a toxin only when infected by a specific bacteriophage. What is the genetic mechanism responsible for this phenomenon?

Accepted Answer

Lysogenic conversion, where prophage DNA encodes new properties in the host

Question 11

Which of the following best describes the structure of an enveloped virus?

Accepted Answer

A nucleic acid core surrounded by a protein capsid and an outer lipid membrane derived from the host cell

Question 12

Which of the following laboratory techniques is NOT commonly used to identify viruses?

Accepted Answer

Gram staining

Question 13

A patient is infected with Hepatitis B virus, which replicates its DNA from an RNA intermediary. Which enzyme is essential for this process?

Accepted Answer

Reverse transcriptase

Question 14

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

Accepted Answer

They require host cell machinery for replication and lack their own ribosomes and ATP-generating mechanisms.

Question 15

Which of the following is a correct distinction between viroids, virusoids, and prions?

Accepted Answer

Viroids are naked RNA molecules infecting plants; virusoids are RNA molecules enclosed in a protein coat requiring co-infection; prions are infectious proteins.

Question 16

A virus with a segmented, negative-sense, single-stranded RNA genome undergoes genetic reassortment with another strain, resulting in a new subtype. Which process is responsible for this?

Accepted Answer

Antigenic shift

Question 17

Which of the following best describes the process of viral budding in enveloped animal viruses?

Accepted Answer

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

Question 18

Which of the following best explains how an RNA virus can cause cancer if it does not have DNA to insert into the host genome?

Accepted Answer

The RNA virus uses reverse transcriptase to synthesize DNA from its RNA genome, which then integrates into the host genome.

Question 19

Which of the following is a real-world example of a disease caused by a prion?

Accepted Answer

Creutzfeldt-Jakob disease

Viruses, Viroids, and Prions: Structure, Classification, and Life Cycles

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