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

$$ PFU\ per\ mL = \frac{\text{Number of plaques}}{\text{Dilution factor} \times \text{Volume plated (mL)}} $$

Question 1

Which of the following best describes the function of a viral capsid?

Accepted Answer

It protects the viral genome and aids in attachment to host cells.

Question 2

A virus with a broad host range is most likely to:

Accepted Answer

Infect multiple species across different kingdoms.

Question 3

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

Accepted Answer

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

Question 4

Which of the following statements about prions is correct?

Accepted Answer

Prions are infectious proteins that lack nucleic acids.

Question 5

A patient is diagnosed with Creutzfeldt-Jakob disease. Which of the following best explains the pathogenesis of this disease?

Accepted Answer

Accumulation of misfolded PrPsc proteins causes clumping in nervous tissue, leading to neurodegeneration.

Question 6

Which of the following best describes the difference between a lytic and a lysogenic viral cycle?

Accepted Answer

The lytic cycle results in immediate destruction of the host cell, while the lysogenic cycle integrates viral DNA into the host genome for a latent period.

Question 7

Which of the following is a correct description of a viral envelope?

Accepted Answer

A lipid bilayer derived from the host cell membrane that surrounds some viruses.

Question 8

During the 1918-1919 Spanish flu pandemic, which of the following factors contributed most to the high mortality rate?

Accepted Answer

The influenza A virus caused severe secondary bacterial infections and had a novel antigenic profile.

Question 9

Which of the following best explains why HIV is able to evade the immune system and establish persistent infections?

Accepted Answer

HIV integrates its genome into host DNA as a provirus, allowing it to remain latent and avoid immune detection.

Question 10

Which of the following is a hallmark of the lytic cycle in bacteriophages?

Accepted Answer

Rapid production of new virions followed by lysis of the host cell.

Question 11

A scientist observes that a virus can only infect liver cells in humans. This specificity is best described as:

Accepted Answer

Tissue tropism

Question 12

Which of the following best describes a viroid?

Accepted Answer

A small, circular RNA molecule that infects plants and lacks a protein coat.

Question 13

Which of the following is NOT a typical capsid structure found in viruses?

Accepted Answer

Cuboidal

Question 14

Which of the following best explains the role of spike proteins on enveloped viruses?

Accepted Answer

They mediate attachment and entry into host cells by binding to specific receptors.

Question 15

A temperate bacteriophage infects a bacterial cell and integrates its DNA into the host genome. What is the integrated viral DNA called?

Accepted Answer

Prophage

Question 16

Which of the following steps is unique to the lysogenic cycle and not found in the lytic cycle?

Accepted Answer

Integration of viral DNA into the host genome

Question 17

Which of the following best describes the process of viral uncoating?

Accepted Answer

The removal of the capsid to release the viral genome into the host cell.

Question 18

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

Accepted Answer

HIV infection, where the virus remains in the host as a provirus for years.

Question 19

Which of the following best explains why bacteriophage plaques appear as clear zones on a bacterial lawn?

Accepted Answer

They represent areas where bacterial cells have been lysed by viral infection.

Question 20

Which of the following is a correct sequence of the four basic steps that all viral replication cycles must achieve?

Accepted Answer

Attachment, entry, synthesis, release

Viruses, Viroids, and Prions: Microbiology Study Notes

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