Question 1

Which of the following best distinguishes a virus from a bacterium?

Accepted Answer

Viruses require a host cell for reproduction, while bacteria can reproduce independently.

Question 2

A scientist is studying a virus with a lipid envelope and spike proteins. Which of the following statements about this virus is correct?

Accepted Answer

The envelope is derived in part from the host cell membrane during viral budding.

Question 3

Which method is most appropriate for quantifying bacteriophages in a laboratory setting?

Accepted Answer

Counting plaques formed on a bacterial lawn (plaque-forming units).

Question 4

A researcher wants to culture an animal virus for vaccine production. Which of the following is NOT a standard method for culturing animal viruses?

Accepted Answer

Growing the virus on nutrient agar plates without host cells.

Question 5

Which of the following laboratory techniques is LEAST likely to be used for identifying a virus in a clinical sample?

Accepted Answer

Gram staining and light microscopy.

Question 6

During the lytic cycle of a T-even bacteriophage, what is the correct sequence of events after the phage attaches to the bacterial cell?

Accepted Answer

Penetration, biosynthesis, maturation, release

Question 7

Which of the following is a possible outcome of lysogeny in bacteria infected by a temperate phage?

Accepted Answer

The bacterium becomes immune to reinfection by the same phage.

Question 8

A patient is infected with a positive-sense RNA virus. Which of the following best describes the biosynthesis of this virus?

Accepted Answer

The viral RNA is directly translated as mRNA in the cytoplasm.

Question 9

Which of the following best explains why retroviruses are associated with certain cancers?

Accepted Answer

Retroviruses use reverse transcriptase to integrate their DNA into the host genome, potentially activating oncogenes.

Question 10

A cell line derived from human tissue is able to divide for about 100 generations before stopping. This cell line is best described as:

Accepted Answer

A diploid cell line

Question 11

Which of the following statements about latent and persistent viral infections is correct?

Accepted Answer

Latent infections can reactivate when host immunity changes.

Question 12

Which of the following is a correct definition of a viroid?

Accepted Answer

A short piece of naked RNA with no protein coat.

Question 13

A patient develops subacute sclerosing panencephalitis years after a measles infection. This is an example of:

Accepted Answer

A persistent viral infection

Question 14

Which of the following best describes how a prion can be infectious?

Accepted Answer

A prion is a misfolded protein that induces normal proteins to misfold, leading to disease.

Question 15

Which of the following is a real-world example of a latent viral infection?

Accepted Answer

Varicellovirus causing chickenpox and later reactivating as shingles

Question 16

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

Accepted Answer

Phage conversion

Question 17

Which of the following equations correctly represents the calculation of plaque-forming units (PFU) per mL in a bacteriophage assay?

Accepted Answer

$$\mathrm{PFU\ per\ mL} = \frac{	ext{Number of plaques}}{	ext{Dilution factor} 	imes 	ext{Volume plated (mL)}}$$

Question 18

A scientist is studying a negative-sense RNA virus. Which enzyme must be present for the virus to replicate in the host cell?

Accepted Answer

RNA-dependent RNA polymerase

Question 19

Which of the following best describes the process of specialized transduction?

Accepted Answer

A phage transfers specific bacterial genes adjacent to the prophage during excision from the host genome.

Question 20

Which of the following statements about the biosynthesis of DNA viruses in animal cells is correct?

Accepted Answer

Capsid proteins are synthesized in the cytoplasm and then move into the nucleus for assembly.

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