Question 1

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

Accepted Answer

They require host cell machinery to replicate their nucleic acids and synthesize proteins.

Question 2

A virus with a helical capsid and an envelope is most likely to enter an animal cell by which mechanism?

Accepted Answer

Fusion with the host cell membrane

Question 3

Which of the following statements about viral genomes is correct?

Accepted Answer

Viral genomes can be either DNA or RNA, single or double stranded, linear or circular.

Question 4

During the lysogenic cycle of a bacteriophage, what is the fate of the viral DNA?

Accepted Answer

It is integrated into the host cell's chromosome and replicated along with host DNA.

Question 5

Which of the following best explains why antiviral drugs are often less effective than antibiotics?

Accepted Answer

Viruses lack metabolic pathways targeted by most drugs.

Question 6

A patient is diagnosed with a persistent viral infection. Which of the following best describes this condition?

Accepted Answer

The virus causes disease gradually over a long period, often leading to fatality.

Question 7

Which of the following is a unique property of retroviruses compared to other RNA viruses?

Accepted Answer

They use reverse transcriptase to synthesize DNA from their RNA genome.

Question 8

Which of the following is a consequence of lysogenic conversion in bacteria?

Accepted Answer

The host cell may acquire new properties, such as toxin production.

Question 9

Which laboratory method is commonly used to quantify the number of infectious bacteriophages in a sample?

Accepted Answer

Plaque assay (counting plaque-forming units, PFU)

Question 10

Which of the following best describes a viroid?

Accepted Answer

A naked, circular, single-stranded RNA molecule that infects plants

Question 11

A prion causes disease by which of the following mechanisms?

Accepted Answer

Inducing misfolding of normal host proteins into infectious forms

Question 12

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

Accepted Answer

Attachment → Entry → Synthesis → Assembly → Release

Question 13

Which of the following is a key difference between positive-sense and negative-sense single-stranded RNA viruses?

Accepted Answer

Positive-sense RNA can be directly translated into proteins, while negative-sense RNA must first be transcribed into a complementary strand.

Question 14

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

Accepted Answer

They cannot carry out metabolism or reproduce independently.

Question 15

A scientist is culturing a newly discovered animal virus. Which of the following would NOT be an appropriate method for culturing this virus?

Accepted Answer

Using a nutrient agar plate without host cells

Question 16

Which of the following is a real-world example of a virus causing cancer in humans?

Accepted Answer

HIV causing Kaposi's sarcoma

Question 17

Which of the following best describes specialized transduction?

Accepted Answer

Transfer of specific bacterial genes adjacent to a prophage during lysogenic cycle

Question 18

Which of the following is a plausible reason why some viruses are highly mutable and can evade immune responses?

Accepted Answer

They have a phospholipid envelope with rapidly changing glycoprotein spikes.

Question 19

Which of the following is a correct statement about the host range of viruses?

Accepted Answer

A virus's host range is determined by its ability to attach to specific receptors and utilize host machinery.

Question 20

Which of the following best describes the eclipse period in animal virus replication?

Accepted Answer

The period after entry when the virus is disassembled and no infectious particles are detected.

Characterizing and Classifying Viruses, Viroids, and Prions

Study Guide - Practice Questions