Question 1

Which of the following best explains why viruses are classified as nonliving microbes?

Accepted Answer

They are acellular, lack metabolic processes, and cannot replicate independently.

Question 2

A scientist observes a virus with a helical capsid, a lipid envelope, and glycoprotein spikes. Which function do the spikes primarily serve?

Accepted Answer

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

Question 3

Which statement correctly describes the genomic variations among viruses?

Accepted Answer

Viral genomes can be DNA or RNA, single- or double-stranded, linear, circular, or segmented.

Question 4

A single-stranded antisense RNA virus must produce mRNA before protein synthesis. Which enzyme is required for this process?

Accepted Answer

RNA-dependent RNA polymerase

Question 5

Why do RNA viruses evolve faster than DNA viruses?

Accepted Answer

RNA polymerases lack proofreading capabilities, resulting in higher mutation rates.

Question 6

Which of the following best describes antigenic shift in influenza viruses?

Accepted Answer

Major genetic changes due to reassortment of segmented genomes, producing new viral strains.

Question 7

A virus is classified as belonging to the family Herpesviridae. According to ICTV conventions, which is the correct format for the family name?

Accepted Answer

Herpesviridae (italicized)

Question 8

Host range and tropism are important concepts in virology. Which scenario best illustrates viral tropism?

Accepted Answer

A virus infects only liver cells within humans due to specific receptor binding.

Question 9

During the lytic replication cycle of a bacteriophage, which step directly results in the destruction of the host cell?

Accepted Answer

Release

Question 10

Which of the following is a key difference between enveloped and naked animal viruses during the release step?

Accepted Answer

Enveloped viruses are released by budding, acquiring a lipid envelope; naked viruses are released by lysing the host cell.

Question 11

A patient is diagnosed with a persistent viral infection that periodically reactivates, causing symptoms. Which type of infection is this?

Accepted Answer

Latent persistent infection

Question 12

Which virus is classified as oncogenic and is associated with cervical cancer?

Accepted Answer

Human papilloma virus (HPV)

Question 13

A researcher uses a plaque assay to quantify bacteriophages. If 50 plaques are counted on a plate inoculated with 0.1 mL of a $$10^{-6}$$ dilution, what is the viral titer in PFU/mL?

Accepted Answer

$$5 	imes 10$$^{7}$$ PFU/mL

Question 14

Which laboratory method is most suitable for detecting viral genetic material in early infection?

Accepted Answer

PCR or RT-PCR

Question 15

Which antiviral drug mechanism is correctly matched with its target?

Accepted Answer

Acyclovir: inhibits viral genome synthesis as a nucleoside analog

Question 16

Which statement about prions is correct?

Accepted Answer

Prions are infectious proteins that lack genetic material and cause spongiform encephalopathies.

Question 17

A virus with a segmented RNA genome undergoes reassortment with another strain in the same host. What is the most likely outcome?

Accepted Answer

Antigenic shift producing a new viral strain with altered spike proteins.

Question 18

Which step in animal virus replication is unique compared to bacteriophage replication?

Accepted Answer

Uncoating of the viral genome by host enzymes.

Question 19

A patient receives a positive ELISA result for a viral antigen. What is a limitation of this test?

Accepted Answer

It cannot detect viral genetic material.

Question 20

Which of the following best describes the process by which a retrovirus produces mRNA for protein synthesis?

Accepted Answer

Reverse transcriptase converts RNA into double-stranded DNA, which integrates into the host genome and is transcribed into mRNA.

Viruses and Prions: Structure, Replication, Evolution, and Clinical Aspects

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