Question 1

Which of the following statements best describes the main structural difference between naked and enveloped viruses?

Accepted Answer

Enveloped viruses have a phospholipid membrane (envelope) surrounding the nucleocapsid, which is obtained from the host cell, while naked viruses lack this envelope.

Question 2

Which of the following is NOT a characteristic of prions?

Accepted Answer

They contain both DNA and RNA.

Question 3

In the Baltimore classification, which enzyme is required for replication of a virus with a dsDNA genome that does NOT use reverse transcriptase?

Accepted Answer

DNA polymerase

Question 4

Refer to the first image. The right panel shows bovine spleen cells after infection with Parapoxvirus. What is the most likely explanation for the observed cellular changes?

Accepted Answer

The cells are exhibiting cytopathic effects caused by viral infection.

Question 5

Which of the following best describes the latent period in viral growth?

Accepted Answer

It is the period when the virus is solely inside the host cell, including the eclipse and maturation phases.

Question 6

Which of the following is a key difference between the lytic and lysogenic cycles of bacteriophages?

Accepted Answer

The lysogenic cycle involves a period of dormancy where the viral genome replicates along with the host genome, while the lytic cycle results in immediate destruction of the host cell.

Question 7

What is the main function of lysozyme during the release stage of T4 bacteriophage replication?

Accepted Answer

Lysozyme breaks down the bacterial cell wall, allowing release of new virions.

Question 8

Which cellular barriers must the T4 bacteriophage breach to release new virions from a bacterial cell?

Accepted Answer

Both the cytoplasmic membrane and the peptidoglycan layer

Question 9

Which of the following best describes lysogenic conversion?

Accepted Answer

It is the alteration of the host phenotype due to bacteriophage genes, such as increased virulence in Vibrio cholera.

Question 10

Which of the following is TRUE regarding viral plaques and plaque forming units (pfu)?

Accepted Answer

Plaque forming units (pfu) are used to quantify the number of viruses capable of forming plaques in a cell culture.

Question 11

Which of the following is NOT a method used for viral detection and diagnosis?

Accepted Answer

Gram staining of viral particles

Question 12

Refer to the second image. Which panel (a or b) most likely shows cells exhibiting cytopathic effects due to viral infection?

Accepted Answer

Panel (b), because the cells show abnormal morphology and detachment.

Question 13

Which of the following is an example of a latent viral infection?

Accepted Answer

Measles or shingles

Question 14

Which of the following is an example of a persistent viral infection?

Accepted Answer

Hepatitis B virus (HBV)

Question 15

What is the genetic material of prions?

Accepted Answer

Protein

Question 16

How do prions cause pathogenesis in the host?

Accepted Answer

By accumulating prion proteins that kill brain cells and form plaques in the CNS

Question 17

Which of the following best describes the host range of a virus?

Accepted Answer

The type of organism(s) that the virus can infect, determined by the host cell surface receptor

Question 18

According to the Baltimore classification diagram (third image), which enzyme is required for replication of a Class VI (+ssRNA) virus?

Accepted Answer

Reverse transcriptase

Question 19

Which of the following is TRUE about viral cell tropism?

Accepted Answer

It is determined by tissue-specific viral receptors on the host cell surface.

Question 20

Which of the following best describes the process of viral genome replication in a Class III (dsRNA) virus according to the Baltimore classification?

Accepted Answer

Replication is carried out by RNA-dependent RNA polymerase (RdRp).

Viruses and Prions: Structure, Replication, and Pathogenesis

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