Question 1

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

Accepted Answer

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

Question 2

A scientist observes a virus with a helical capsid structure under a transmission electron microscope. Which virus is most likely being observed?

Accepted Answer

Rabies virus

Question 3

Which of the following best describes the eclipse period in the one-step growth curve of viral replication?

Accepted Answer

The period after viral entry but before new virions are released from the host cell.

Question 4

Which of the following is a unique feature of viruses that distinguishes them from both typical bacteria and rickettsias/chlamydias?

Accepted Answer

Lack of both ribosomes and ATP-generating metabolism

Question 5

During the lytic cycle of a T-even bacteriophage, what is the primary function of the enzyme lysozyme?

Accepted Answer

To break down the bacterial cell wall for DNA injection and later for cell lysis

Question 6

A patient is diagnosed with a persistent viral infection that gradually worsens over years and is ultimately fatal. Which of the following viruses is most likely responsible?

Accepted Answer

Measles virus (causing subacute sclerosing panencephalitis)

Question 7

Which of the following best explains why animal viruses are often grown in embryonated eggs for vaccine production?

Accepted Answer

Embryonated eggs provide a living environment that supports viral replication and allows for easy detection of viral growth.

Question 8

Which of the following is a correct statement about the genetic material of viruses?

Accepted Answer

A virus contains either DNA or RNA, but never both.

Question 9

A bacterium acquires the ability to produce a toxin after infection by a bacteriophage. This phenomenon is best described as:

Accepted Answer

Phage conversion

Question 10

Which of the following best describes the role of reverse transcriptase in the replication of retroviruses?

Accepted Answer

It synthesizes DNA from an RNA template, allowing integration into the host genome.

Question 11

Which of the following is a characteristic of latent viral infections?

Accepted Answer

The virus remains dormant in the host cell and may reactivate later.

Question 12

Which of the following is true regarding prions?

Accepted Answer

They are infectious proteins that can be transmitted by ingestion, transplant, or surgical instruments.

Question 13

A plant exhibits symptoms of disease after being exposed to a short piece of naked RNA. Which infectious agent is most likely responsible?

Accepted Answer

Viroid

Question 14

Which of the following best explains why viruses are not sensitive to antibiotics but are sensitive to interferon?

Accepted Answer

Viruses lack the metabolic pathways targeted by antibiotics but can be inhibited by host immune responses such as interferon.

Question 15

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

Accepted Answer

Attachment → Penetration → Biosynthesis → Maturation → Release

Question 16

A virus is found to have a polyhedral capsid and is nonenveloped. Which of the following viruses fits this description?

Accepted Answer

Adenovirus

Question 17

Which of the following best describes specialized transduction?

Accepted Answer

A process in which specific bacterial genes are transferred to another bacterium via a lysogenic phage.

Question 18

Which of the following is a likely outcome of lysogeny in a bacterial population?

Accepted Answer

The bacterial cells become immune to reinfection by the same phage.

Question 19

Which of the following best explains why plant viruses often require wounds or insect vectors to infect plant cells?

Accepted Answer

Plant cells have an impermeable cell wall that prevents viral entry unless it is breached.

Question 20

A patient is diagnosed with adult T cell leukemia. Which of the following viruses is most likely responsible for this disease?

Accepted Answer

HTLV-1 (Human T-cell Leukemia Virus type 1)

Viruses: Structure, Multiplication, and Comparison with Bacteria

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