Question 1

Which of the following best describes the mechanism by which an enveloped animal virus typically exits its host cell?

Accepted Answer

By budding, acquiring a portion of the host cell membrane as its envelope.

Question 2

A scientist is culturing a virus that requires a DNA intermediate for replication, even though its genome is RNA. Which enzyme is essential for this virus's replication?

Accepted Answer

Reverse transcriptase

Question 3

Which of the following is a key difference between bacteriophage and animal virus replication?

Accepted Answer

Animal viruses may enter host cells by membrane fusion, while bacteriophages inject their genome.

Question 4

Which of the following statements about prions is correct?

Accepted Answer

Prions are infectious proteins that cause normal cellular proteins to misfold into a disease-causing form.

Question 5

A patient is diagnosed with a spongiform encephalopathy. Which of the following is the most likely cause?

Accepted Answer

Accumulation of prion proteins with β-pleated sheets in the brain.

Question 6

Which of the following best explains why viruses cannot be cultured in standard microbiological media?

Accepted Answer

Viruses require living host cells for replication.

Question 7

Which of the following is a characteristic of viroids?

Accepted Answer

They are small, circular pieces of single-stranded RNA that infect plants.

Question 8

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

Accepted Answer

A zone where bacterial cells have been lysed by a single phage particle.

Question 9

Which of the following is a real-world example of a cancer caused by a virus?

Accepted Answer

Cervical cancer caused by human papillomavirus (HPV).

Question 10

Which of the following best describes the process of latency in animal viruses?

Accepted Answer

The viral genome remains dormant in the host cell, sometimes integrating into host DNA.

Question 11

Which of the following is NOT a method by which animal viruses can enter host cells?

Accepted Answer

Binary fission

Question 12

Which of the following statements about the sterilization of prions is correct?

Accepted Answer

Prions are destroyed by incineration or autoclaving in concentrated sodium hydroxide.

Question 13

Which of the following best explains why embryonated chicken eggs are commonly used for culturing certain viruses?

Accepted Answer

They are inexpensive, free of contaminating microbes, and provide a nourishing environment.

Question 14

Which of the following is a plausible reason why some viruses are associated with cancer development?

Accepted Answer

They can carry oncogenes or disrupt tumor suppressor genes in host DNA.

Question 15

Which of the following is true regarding the replication site of most DNA and RNA animal viruses?

Accepted Answer

Most DNA viruses replicate in the nucleus, while most RNA viruses replicate in the cytoplasm.

Question 16

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

Accepted Answer

A small, circular, single-stranded RNA molecule lacking a capsid.

Question 17

A virus is found to cause cancer by integrating its genome into the host DNA and disrupting a gene for a tumor repressor protein. According to the oncogene theory, what is the likely result?

Accepted Answer

Uncontrolled cell division leading to cancer.

Question 18

Which of the following is a distinguishing feature of prion diseases compared to viral diseases?

Accepted Answer

Prion diseases involve misfolded proteins without nucleic acids, while viral diseases involve nucleic acids.

Question 19

Which of the following best explains why viroid RNA causes disease in plants?

Accepted Answer

Viroid RNA binds to complementary plant RNA, leading to degradation by plant enzymes.

Characterizing and Classifying Viruses, Viroids, and Prions

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