Question 1

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

Accepted Answer

They require the metabolic machinery of host cells to synthesize viral proteins and replicate their genome.

Question 2

A scientist is studying a virus with a single-stranded RNA genome that serves directly as mRNA upon infection. Which enzyme is essential for this virus to replicate its genome?

Accepted Answer

RNA-dependent RNA polymerase

Question 3

Which of the following best explains the process of 'assembly' (maturation) in the viral life cycle?

Accepted Answer

It is the spontaneous crystallization of capsid proteins and viral genome into mature virions when their concentrations are sufficient.

Question 4

A retrovirus infects a host cell. Which sequence of events correctly describes the synthesis of viral proteins?

Accepted Answer

Viral RNA is reverse transcribed into DNA, which integrates into the host genome; host RNA polymerase then transcribes viral genes into mRNA, which is translated into proteins.

Question 5

Which of the following is a unique property of prions compared to viruses?

Accepted Answer

They are composed solely of misfolded proteins without any nucleic acid.

Question 6

A patient is diagnosed with a disease caused by a prion. Which of the following best describes the pathogenesis of this disease?

Accepted Answer

The prion protein induces misfolding of normal host proteins, leading to neurodegeneration.

Question 7

Which of the following best explains why some plant viruses can be transmitted by insects but not by direct contact between plants?

Accepted Answer

Plant viruses such as viroids are small RNA molecules that require a vector, like insects, to breach the plant cell wall.

Question 8

Which of the following is a function of reverse transcriptase in retroviruses?

Accepted Answer

It synthesizes a complementary DNA strand from an RNA template.

Question 9

A virus with a double-stranded DNA genome infects a host cell. Which of the following steps is LEAST likely to occur during its replication?

Accepted Answer

Viral DNA is reverse transcribed into RNA.

Question 10

Which of the following best describes the role of protease in the HIV life cycle?

Accepted Answer

It cleaves the long polypeptide translated from viral mRNA into functional viral proteins.

Question 11

Which of the following statements about oncogenic viruses is correct?

Accepted Answer

Oncogenic viruses can cause cancer by introducing viral oncogenes or activating host proto-oncogenes.

Question 12

A researcher is studying a virus that cannot uncoat in a plant cell due to high concentrations of coat protein. What is the most likely outcome for the virus?

Accepted Answer

The virus will be unable to proceed with infection and its life cycle will be halted.

Question 13

Which of the following best explains why viroids are distinct from viruses?

Accepted Answer

Viroids are small, circular RNA molecules without a protein coat, infecting plants.

Question 14

Which of the following equations best represents the synthesis of complementary DNA by reverse transcriptase?

Accepted Answer

$$cDNA = RT(RNA)$$

Question 15

A virus with a positive-sense RNA genome (+RNA) infects a cell. Which of the following best describes the initial steps of its replication?

Accepted Answer

The +RNA is directly translated by host ribosomes to produce viral proteins.

Question 16

Which of the following is a plausible reason why protease inhibitors are effective in HIV therapy?

Accepted Answer

They block the cleavage of viral polyproteins, preventing the formation of functional viral proteins.

Question 17

Which of the following best describes the difference between viral assembly and bacterial cell division?

Accepted Answer

Viral assembly involves the spontaneous combination of viral components, while bacterial cell division involves binary fission and growth.

Question 18

A virus is found to have no ribosomes, no metabolic enzymes, and cannot generate ATP. What is the most likely explanation for how it produces proteins?

Accepted Answer

It hijacks the host cell's ribosomes and metabolic machinery to synthesize proteins.

Question 19

Which of the following best explains why some retroviruses are oncogenic?

Accepted Answer

They carry genes that can activate host proto-oncogenes or introduce viral oncogenes, disrupting normal cell regulation.

Viruses: Structure, Physiology, and Unique Infectious Agents ~ Chp 13

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