Question 1

Which of the following best describes the replication strategy of pox viruses?

Accepted Answer

Replication occurs in the cytoplasm and involves viral-encoded enzymes.

Question 2

Adenoviruses avoid the synthesis of a lagging strand during DNA replication. What is the molecular basis for this?

Accepted Answer

They use a protein primer to initiate DNA synthesis at both ends of the linear genome.

Question 3

Polyomavirus SV40 can induce cancer in nonpermissive host cells. What is the key event that leads to tumor formation?

Accepted Answer

Viral DNA integrates into the host genome, altering cellular gene expression.

Question 4

During herpesvirus replication, three classes of mRNA are produced. What is the correct order of their expression?

Accepted Answer

Immediate-early, early, late

Question 5

Which statement correctly describes the replication of positive-strand RNA viruses?

Accepted Answer

Their RNA genome is directly used as mRNA for protein synthesis.

Question 6

Poliovirus produces a single long polyprotein from its RNA genome. What is the fate of this polyprotein?

Accepted Answer

It undergoes self-cleavage to generate multiple functional viral proteins.

Question 7

Which of the following is a similarity between the replication cycles of polioviruses and coronaviruses?

Accepted Answer

Both use RNA replicase to synthesize complementary negative-strand RNA.

Question 8

Negative-strand RNA viruses require which enzyme for replication, and why?

Accepted Answer

RNA replicase, because their genome is complementary to mRNA and cannot be directly translated.

Question 9

Influenza virus can evade the immune system through antigenic drift. What is the molecular basis of antigenic drift?

Accepted Answer

Subtle mutations in the genes encoding hemagglutinin and neuraminidase.

Question 10

Antigenic shift in influenza virus is responsible for major pandemics. What is the key event in antigenic shift?

Accepted Answer

Reassortment of RNA segments from two genetically distinct viruses infecting the same cell.

Question 11

Retroviruses such as HIV use reverse transcriptase during their replication cycle. What is the function of reverse transcriptase?

Accepted Answer

It copies the viral RNA genome into DNA.

Question 12

Prions cause transmissible spongiform encephalopathies. What is the molecular mechanism underlying prion diseases?

Accepted Answer

Prion proteins misfold and aggregate, leading to neuronal damage.

Question 13

Which of the following is NOT a prion disease?

Accepted Answer

Hepatitis A

Question 14

Which virus is known for having a segmented genome and surface proteins that interact with host cell sialic acid?

Accepted Answer

Influenza virus

Question 15

What is the role of hemagglutinin in influenza virus infection?

Accepted Answer

It binds to sialic acid on host cells, facilitating viral entry.

Question 16

Which of the following equations correctly represents the relationship between viral genome type and mRNA synthesis for Class IV viruses?

Accepted Answer

$$\mathrm{genomic\ RNA\ ( + )} \rightarrow \mathrm{mRNA\ ( + )}$$

Question 17

Which virus is an example of a negative-strand RNA virus that requires RNA replicase for mRNA synthesis?

Accepted Answer

Rabies virus

Question 18

Which of the following best explains why prion diseases are resistant to proteases?

Accepted Answer

Prion proteins misfold into a conformation that is resistant to protease digestion.

Question 19

Which of the following viruses replicates through an RNA intermediate despite having a DNA genome?

Accepted Answer

Hepadnavirus

Question 20

A patient presents with rapidly progressive dementia and myoclonus. Which prion disease is most likely?

Accepted Answer

Creutzfeldt-Jakob Disease (CJD)

Viral Genomes, Replication Strategies, and Subviral Agents

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