Question 1

Which of the following statements best describes a fundamental characteristic shared by all viruses?

Accepted Answer

They are obligate intracellular parasites that require a host cell for replication.

Question 2

Which of the following is NOT one of the six characteristics in which viruses differ?

Accepted Answer

Presence or absence of a cell wall

Question 3

During the lytic replication cycle of bacteriophage T4, what is the correct sequence of events?

Accepted Answer

Attachment, penetration, synthesis, assembly, release

Question 4

A graph of burst size and burst time for a bacteriophage shows a plateau after a certain time. What does this plateau represent?

Accepted Answer

The maximum number of virions released per infected cell.

Question 5

Which of the following best describes lysogenic replication of bacteriophage lambda?

Accepted Answer

The phage DNA integrates into the host genome and is replicated along with it without immediately destroying the host.

Question 6

Which of the following is NOT a mechanism of animal virus entry into host cells?

Accepted Answer

Transduction

Question 7

A single-stranded positive-sense RNA virus ($$ssRNA^+) $$infects a cell. Which process must occur for this virus to replicate?

Accepted Answer

The viral RNA is directly translated by host ribosomes to produce viral proteins.

Question 8

Which of the following best defines a persistent infection?

Accepted Answer

An infection in which the virus remains in the host for long periods, often with ongoing production of virions.

Question 9

How does latency of animal viruses differ from lysogeny in bacteriophages?

Accepted Answer

Latent animal viruses may remain dormant as episomes in the cytoplasm or integrate into the host genome, while lysogenic phages always integrate into the bacterial chromosome.

Question 10

Which of the following terms describes the spread of cancer cells from the original tumor to distant sites in the body?

Accepted Answer

Metastasis

Question 11

According to the oncogene theory of cancer induction, how can viruses contribute to the development of cancer?

Accepted Answer

By introducing oncogenes or activating host proto-oncogenes, leading to uncontrolled cell division.

Question 12

Which of the following is NOT a main method used to culture viruses in the laboratory?

Accepted Answer

Growth on nutrient agar plates

Question 13

Which statement best describes viroids?

Accepted Answer

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

Question 14

Which of the following statements about prions is correct?

Accepted Answer

Prions are infectious proteins that propagate by inducing misfolding of normal host proteins.

Question 15

A patient is diagnosed with a persistent viral infection. Which of the following best explains the likely course of this infection?

Accepted Answer

The virus remains in the host, producing low levels of virions over a long period.

Question 16

Which of the following best describes the replication process of retroviruses?

Accepted Answer

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

Question 17

A scientist is studying a new virus and finds that it has a double-stranded RNA genome. Which of the following statements about its replication is most accurate?

Accepted Answer

The virus must carry its own RNA-dependent RNA polymerase to replicate its genome.

Question 18

Which of the following equations best represents the calculation of burst size in a lytic bacteriophage infection?

Accepted Answer

$$	ext{Burst size} = \frac{	ext{Total number of released virions}}{	ext{Number of infected cells}}$$

Question 19

A researcher observes that a virus can only infect cells with a specific surface protein. Which viral property does this observation illustrate?

Accepted Answer

Host range specificity determined by viral attachment proteins.

Question 20

Which of the following best explains why prion diseases are difficult to treat and control?

Accepted Answer

Prions lack nucleic acids and are resistant to standard sterilization methods.

Microbiology Study Guide: Viruses, Viroids, and Prions

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