Question 1

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

Accepted Answer

They require living host cells to multiply because they lack ribosomes and an ATP-generating mechanism.

Question 2

A scientist is studying a virus that infects only a specific type of animal cell. What determines this virus's host range?

Accepted Answer

The specific host attachment sites and cellular factors present on the host cell.

Question 3

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

Accepted Answer

A virion is a complete, fully developed viral particle consisting of nucleic acid and a protein coat, and sometimes an envelope.

Question 4

Which of the following viruses is an example of a helical virus?

Accepted Answer

Rabies virus

Question 5

A virus is found to have a genome that is single-stranded RNA, segmented, and enveloped. According to the Baltimore classification, which group does this virus most likely belong to?

Accepted Answer

Group V: Negative-sense single-stranded RNA viruses

Question 6

Which laboratory method is most appropriate for quantifying the number of infectious bacteriophages in a sample?

Accepted Answer

Counting plaque-forming units (PFU) on a lawn of bacteria

Question 7

A researcher is developing a vaccine and needs to grow large quantities of an animal virus. Which method is commonly used for this purpose and why?

Accepted Answer

Injection into embryonated eggs, because viral growth is signaled by changes or death of the embryo.

Question 8

Which of the following best describes the cytopathic effect (CPE) in cell cultures?

Accepted Answer

Visible changes or deterioration of monolayer cells due to viral infection.

Question 9

Which of the following is a key difference between the multiplication of bacteriophages and animal viruses?

Accepted Answer

Animal viruses enter host cells by endocytosis or fusion, while bacteriophages inject their DNA into the host cell.

Question 10

A patient develops cervical cancer years after a viral infection. Which of the following best explains the mechanism by which the virus caused cancer?

Accepted Answer

The viral genome integrated into the host DNA, transforming proto-oncogenes into oncogenes.

Question 11

Which of the following viruses is associated with the development of Burkitt’s lymphoma?

Accepted Answer

Epstein-Barr virus (Herpesviridae)

Question 12

A patient presents with cold sores that recur during periods of stress. Which type of infection is this, and which virus is responsible?

Accepted Answer

Latent infection; Herpes simplex virus (HHV-1)

Question 13

Which of the following best describes prions?

Accepted Answer

Proteinaceous infectious particles that cause spongiform encephalopathies by converting normal host proteins into misfolded forms.

Question 14

Which of the following laboratory techniques is most useful for identifying a virus based on its genetic material?

Accepted Answer

Polymerase chain reaction (PCR)

Question 15

A virus is found to be sensitive to interferon but not to antibiotics. Which of the following is the most likely explanation?

Accepted Answer

Viruses lack ribosomes and are not affected by antibiotics, but interferon can inhibit viral replication.

Question 16

Which of the following best explains why retroviruses are unique among RNA viruses?

Accepted Answer

They use reverse transcriptase to synthesize DNA from their RNA genome, which can integrate into the host genome.

Question 17

A laboratory technician observes a monolayer of cells in culture that begins to show irregular shapes and loss of contact inhibition after viral infection. What is the most likely explanation?

Accepted Answer

The cells have been transformed by an oncogenic virus, leading to cancerous properties.

Question 18

Which of the following is a characteristic of a persistent viral infection?

Accepted Answer

The virus is continuously released from the host cell over a long period, often leading to fatal outcomes.

Question 19

A patient is diagnosed with subacute sclerosing panencephalitis (SSPE) years after recovering from measles. What type of infection does this represent?

Accepted Answer

Persistent viral infection

Viruses, Viroids, and Prions: Structure, Classification, and Pathogenicity

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