Question 1

Which of the following best explains why viruses are generally considered non-living entities?

Accepted Answer

They lack metabolic activity and cannot reproduce independently outside of a host cell.

Question 2

A scientist observes a virus with a lipid envelope and spike proteins. Which of the following is most likely true about this virus?

Accepted Answer

It acquired its envelope from the host cell membrane during release and uses spike proteins for host recognition.

Question 3

Which of the following statements correctly distinguishes between the lytic and lysogenic cycles of bacteriophage infection?

Accepted Answer

The lytic cycle results in the immediate destruction of the host cell, while the lysogenic cycle allows the viral genome to persist within the host without killing it.

Question 4

A viral genome is found to be single-stranded RNA. Which of the following is true regarding the genetic material of viruses?

Accepted Answer

Viruses can have either DNA or RNA, which may be single- or double-stranded.

Question 5

During the lytic cycle, which enzyme is most critical for degrading the bacterial cell wall to allow release of new virions?

Accepted Answer

Lysozyme

Question 6

A bacteriophage infects a gram-positive bacterium. Compared to a gram-negative infection, what is a likely adaptation of the phage's lysozyme?

Accepted Answer

It is more active to penetrate the thick peptidoglycan layers of gram-positive bacteria.

Question 7

Which of the following best describes the function of viral spike proteins?

Accepted Answer

They allow the virus to evade the immune system and recognize specific host cell receptors.

Question 8

A researcher observes a viral infection in which the host cell survives and continues to divide, passing the viral genome to its progeny. Which viral life cycle is most likely occurring?

Accepted Answer

Lysogenic cycle

Question 9

Which of the following is a key reason why viruses with large capsids tend to infect larger host cells?

Accepted Answer

Larger host cells provide more resources and space to assemble and replicate large viral particles.

Question 10

Which of the following best defines a virion?

Accepted Answer

A mature viral particle found outside of a host cell.

Question 11

A patient is diagnosed with a viral infection. The doctor does not prescribe antibiotics. Which of the following best explains this decision?

Accepted Answer

Antibiotics target bacterial structures and processes, not viral replication.

Question 12

Which of the following is a plausible reason for a virus to maintain its genome as a plasmid during the lysogenic cycle rather than integrating into the host chromosome?

Accepted Answer

It allows the virus to avoid the need for specialized enzymes to excise itself from the host genome.

Question 13

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

Accepted Answer

The spectrum of host species and cell types a virus can infect, determined by its surface proteins.

Question 14

A virus is observed to have a genome that is segmented and composed of double-stranded RNA. Which of the following statements is correct?

Accepted Answer

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

Question 15

Which of the following best explains why enveloped viruses are often more susceptible to environmental conditions such as drying and detergents than non-enveloped viruses?

Accepted Answer

Their lipid envelope, derived from the host cell membrane, is easily disrupted by environmental factors.

Question 16

Which of the following is a correct sequence of events in the lytic cycle of a bacteriophage?

Accepted Answer

Attachment → Injection of genome → Host DNA degradation → Synthesis of viral components → Assembly → Lysis

Question 17

A virus infects a cell and expresses a DNA methyltransferase that modifies cytosine bases in its genome. What is the most likely purpose of this modification?

Accepted Answer

To evade host restriction enzymes that target unmethylated cytosine sequences.

Question 18

Which of the following best describes a retrovirus?

Accepted Answer

A virus that uses reverse transcriptase to convert its RNA genome into DNA, which is then integrated into the host genome.

Question 19

A viral plaque assay shows clear plaques and cloudy plaques on a bacterial lawn. What is the most likely explanation for the cloudy plaques?

Accepted Answer

They are areas where bacteria have entered the lysogenic cycle and survived, carrying the viral genome.

Question 20

Which of the following is a real-world implication of the lysogenic cycle for human health or agriculture?

Accepted Answer

It enables viruses to persist in host populations, potentially leading to latent infections or sudden outbreaks when conditions change.

Viruses, Prions, and Viroids: Structure, Classification, and Life Cycles

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