Question 1

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

Accepted Answer

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

Question 2

A scientist passes sap from a diseased tobacco plant through a Chamberland filter and finds that the filtrate still causes disease in healthy plants. What is the most likely explanation for this observation?

Accepted Answer

The infectious agent is smaller than bacteria and can pass through the filter, indicating it is a virus.

Question 3

Which of the following best describes the structure of a naked (non-enveloped) virus?

Accepted Answer

A nucleic acid surrounded only by a protein capsid.

Question 4

Which viral structure is responsible for the attachment of the influenza virus to host cells?

Accepted Answer

Hemagglutinin spikes

Question 5

A virus with a helical capsid and an envelope is most likely to be classified as which of the following?

Accepted Answer

Enveloped helical virus

Question 6

Which of the following is a correct statement about viral genomes?

Accepted Answer

Viral genomes may be single-stranded or double-stranded, and can be either DNA or RNA.

Question 7

Which of the following best explains why antigenic drift in RNA viruses can lead to recurring epidemics?

Accepted Answer

Accumulation of mutations in viral genes leads to genetic variation, allowing the virus to evade immune responses.

Question 8

Which of the following is a distinguishing feature of complex viruses such as bacteriophages?

Accepted Answer

They possess additional structures such as tail fibers, baseplates, and pins attached to the capsid.

Question 9

A virus is found to have a segmented, double-stranded RNA genome. Which of the following viruses fits this description?

Accepted Answer

Rotavirus

Question 10

Which of the following steps is unique to the replication of enveloped animal viruses compared to non-enveloped viruses?

Accepted Answer

Release by budding from the host cell membrane

Question 11

Which of the following equations best represents the exponential increase in the number of virions produced during a lytic infection, where $$N is $$the number of virions, $$n is $$the number of replication cycles, and $$B is $$the burst size per cycle?

Accepted Answer

$$N = B^n$$

Question 12

Which of the following best describes a zoonosis?

Accepted Answer

A disease that can be transmitted from animals to humans.

Question 13

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

Accepted Answer

Antigenic shift results in the formation of a new virus subtype through reassortment of RNA segments from different viruses.

Question 14

Which of the following is true about prions?

Accepted Answer

They are proteinaceous infectious particles that can be inherited or transmitted by ingestion.

Question 15

A patient develops a persistent viral infection that gradually worsens over years and is ultimately fatal. Which of the following best describes this type of infection?

Accepted Answer

Persistent (chronic) viral infection

Question 16

Which of the following is a mechanism by which oncogenic viruses can induce cancer?

Accepted Answer

By integrating their genetic material into host DNA and transforming proto-oncogenes into oncogenes.

Question 17

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

Accepted Answer

They facilitate attachment and entry into host cells.

Question 18

Which of the following is a correct sequence of steps in the replication of a DNA-containing animal virus?

Accepted Answer

Attachment, entry, uncoating, biosynthesis, maturation, release

Question 19

Which of the following best explains why viruses are not classified as living organisms?

Accepted Answer

They lack cellular structure, cannot generate ATP, and do not carry out metabolism independently.

Question 20

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

Accepted Answer

Kuru

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

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