Q: Which of the following equations best represents the calculation for viral titer in a plaque assay, given $$N$$ plaques and a dilution factor $$D$$?

$$\text{Viral Titer} = \frac{N}{\text{Volume} \times D} $$

Question 1

Which of the following best describes why viruses are considered obligate intracellular pathogens?

Accepted Answer

They require living cells to carry out metabolism and replication.

Question 2

A virus with a lipid envelope and glycoprotein spikes is most likely to enter a host cell by which mechanism?

Accepted Answer

Fusion of the viral envelope with the host cell membrane.

Question 3

Which step in the viral replication cycle is unique to animal viruses compared to bacteriophages?

Accepted Answer

Uncoating of the viral genome after entry.

Question 4

A patient is diagnosed with a persistent viral infection that periodically flares up after dormancy. Which type of infection is this?

Accepted Answer

Latent infection

Question 5

Which of the following best explains why RNA viruses evolve more rapidly than DNA viruses?

Accepted Answer

RNA polymerases lack proofreading ability, leading to higher mutation rates.

Question 6

During a pandemic, a new influenza strain emerges due to mixing of genomes from two different viruses infecting the same cell. This process is known as:

Accepted Answer

Antigenic shift

Question 7

Which of the following is NOT a component of a typical virion?

Accepted Answer

Ribosomes for protein synthesis

Question 8

A bacteriophage integrates its genome into the host bacterial DNA and remains dormant. This state is called:

Accepted Answer

Lysogenic cycle

Question 9

Which of the following best describes the Baltimore classification system for viruses?

Accepted Answer

It classifies viruses by genome type and replication method.

Question 10

A virus is classified as 'naked.' What does this mean regarding its structure?

Accepted Answer

It does not have a lipid envelope.

Question 11

Which of the following equations best represents the calculation for viral titer in a plaque assay, given $$N$$ plaques and a dilution factor $$D$$?

Accepted Answer

$$	ext{Viral Titer} = \frac{N}{	ext{Volume} 	imes D} $$

Question 12

Which diagnostic test is most appropriate for detecting viral genetic material in a patient sample?

Accepted Answer

Molecular test (e.g., PCR)

Question 13

A virus that causes cancer by integrating into host DNA and altering cell regulation is known as:

Accepted Answer

Oncogenic virus (oncovirus)

Question 14

Which of the following statements about prions is correct?

Accepted Answer

Prions are infectious proteins that cause neurodegenerative diseases.

Question 15

A virus with a segmented genome undergoes reassortment. What is the most likely outcome?

Accepted Answer

A new viral strain with mixed genetic material from two parent viruses.

Question 16

Which of the following is a plausible reason why antiviral drugs rarely cure viral infections?

Accepted Answer

Viruses have high mutation rates, making drug resistance common.

Question 17

Which viral structure is responsible for host cell recognition and attachment?

Accepted Answer

Spikes (peplomers)

Question 18

A virus is classified as belonging to the order 'Mononegavirales.' Which taxonomic rank is immediately below 'order'?

Accepted Answer

Family

Question 19

Which of the following best describes phage conversion?

Accepted Answer

A prophage provides new traits, such as toxin genes, to the host bacterium.

Question 20

Which equation best represents the relationship between sensitivity, specificity, true positives ($$TP$$), true negatives ($$TN$$), false positives ($$FP$$), and false negatives ($$FN) in a $$diagnostic test?

Accepted Answer

$$	ext{Sensitivity} = \frac{TP}{TP + FN} $$

Viruses and Prions: Structure, Classification, Replication, and Disease

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