Question 1

Which of the following statements best explains why viruses are considered acellular and not alive according to most biologists?

Accepted Answer

Viruses lack the ability to metabolize, grow, reproduce independently, or respond to their environment.

Question 2

A scientist is studying a virus with a genome described as $dsRNA$. Which of the following statements about its replication is correct?

Accepted Answer

The $+RNA$ strand of $dsRNA$ functions in translation, and both strands serve as templates for RNA replication.

Question 3

Which of the following best describes the process of lysogenic conversion in bacteria?

Accepted Answer

A bacterium acquires new traits due to the integration of a prophage into its chromosome.

Question 4

During the lytic replication cycle of bacteriophage T4, what is the primary function of lysozyme?

Accepted Answer

Lysozyme weakens the bacterial cell wall to facilitate entry and later release of viral particles.

Question 5

A virus infects animal cells and is released via budding. Which of the following is a consequence of this release mechanism?

Accepted Answer

The virus acquires an envelope from the host cell membrane, allowing persistent infection.

Question 6

Which of the following viruses requires reverse transcriptase for replication, and what is the role of this enzyme?

Accepted Answer

Hepatitis B virus; reverse transcriptase synthesizes DNA from an RNA intermediate.

Question 7

Which of the following best describes the structure of a viroid?

Accepted Answer

A small, circular piece of RNA with no capsid that infects plants.

Question 8

A patient is diagnosed with variant Creutzfeldt-Jakob disease. Which of the following statements about the causative agent is correct?

Accepted Answer

The disease is caused by a prion, which is an infectious protein that lacks nucleic acids.

Question 9

Which of the following is a major difference between enveloped and nonenveloped (naked) viruses?

Accepted Answer

Enveloped viruses are more fragile due to their membrane, while naked viruses are more easily recognized by the host immune system.

Question 10

Which of the following best describes the replication strategy of a $+ssRNA$ animal virus?

Accepted Answer

The $+ssRNA$ genome is directly translated by host ribosomes, and $-ssRNA$ is synthesized as a template for more $+ssRNA$.

Question 11

A scientist is using a plaque assay to estimate the number of bacteriophages in a sample. What does each plaque represent?

Accepted Answer

A zone where bacteria have been lysed by phages.

Question 12

Which of the following is a correct statement about prion diseases?

Accepted Answer

Prion diseases are caused by misfolded proteins that induce normal proteins to misfold, leading to neuronal death.

Question 13

Which of the following is a key step in the replication cycle of a temperate bacteriophage (such as lambda phage) that distinguishes it from a lytic phage?

Accepted Answer

Integration of the viral genome into the host chromosome as a prophage.

Question 14

Which of the following methods is commonly used to culture animal viruses for vaccine production and is advantageous due to its size and lack of contamination?

Accepted Answer

Embryonated chicken eggs.

Question 15

A virus infects a host cell and its genome is integrated into the host DNA, remaining dormant for years. Which term best describes this viral state?

Accepted Answer

Latency (provirus).

Question 16

Which of the following is a plausible mechanism by which viruses can contribute to cancer development?

Accepted Answer

Viruses activate protooncogenes or inhibit oncogene repressors, leading to uncontrolled cell division.

Question 17

Which of the following best describes the function of capsomeres in viral structure?

Accepted Answer

Capsomeres are protein subunits that form the capsid, protecting the viral genome and aiding in host cell attachment.

Question 18

Which of the following is a correct statement about the culturing of viruses in cell (tissue) culture?

Accepted Answer

Continuous cell cultures are derived from tumor cells and can divide indefinitely.

Question 19

Which of the following is a characteristic of fungal viruses that distinguishes them from most other viruses?

Accepted Answer

Fungal viruses are spread by fusion of infected and uninfected cells and may lack an extracellular stage.

Characterizing and Classifying Viruses, Viroids, and Prions

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