Question 1

Which of the following best describes the structure labeled as 'capsid' in the first image, and what is its primary function in a virus?

Accepted Answer

A protein shell that encases the viral nucleic acid, providing protection and facilitating attachment to host cells.

Question 2

Based on the images and your knowledge, which viral shape is represented by the structure in the sixth image (leftmost virus), and what is a key feature of this shape?

Accepted Answer

Helical; capsomeres are arranged in a spiral around the nucleic acid.

Question 3

Referencing the lytic replication cycle diagram, which step is directly responsible for the sudden increase in the number of infective virions in the medium, as shown in the burst size graph?

Accepted Answer

Release

Question 4

A virus with a segmented, negative-sense single-stranded RNA genome enters a host cell. Which enzyme must it carry or encode to ensure successful replication?

Accepted Answer

RNA-dependent RNA transcriptase

Question 5

Which of the following best explains why enveloped viruses are generally more sensitive to environmental conditions than naked viruses?

Accepted Answer

Their phospholipid envelope is susceptible to desiccation, detergents, and solvents.

Question 6

During lysogenic replication, what is the term for the viral DNA integrated into the bacterial chromosome, and what is a possible consequence of this integration?

Accepted Answer

Prophage; lysogenic conversion can result in new pathogenic traits for the bacterium.

Question 7

Which of the following is a unique feature of retroviruses, such as HIV, during their replication cycle?

Accepted Answer

They synthesize a DNA intermediate from their RNA genome using reverse transcriptase.

Question 8

Which laboratory method is most appropriate for estimating the number of bacteriophages in a sample, as shown in the image with clear zones on a bacterial lawn?

Accepted Answer

Plaque assay

Question 9

A patient is diagnosed with a prion disease. Which of the following statements about prions is correct?

Accepted Answer

Prions are infectious proteins that induce misfolding of normal cellular proteins.

Question 10

Which of the following best describes the process of viral budding, as depicted in the relevant image?

Accepted Answer

The virus acquires its envelope from the host cell membrane as it exits, allowing for persistent infection.

Question 11

Which of the following is a distinguishing feature of viroids compared to viruses?

Accepted Answer

Viroids are small, circular pieces of ssRNA that lack a capsid and do not code for proteins.

Question 12

A scientist is culturing a virus that requires a host cell for replication. Which of the following methods would NOT be suitable for culturing this virus?

Accepted Answer

Growing the virus in nutrient broth without any host cells

Question 13

Which of the following best explains why some viruses are considered to be on the 'threshold of life'?

Accepted Answer

They are inert outside cells but direct synthesis and assembly inside host cells.

Question 14

Which of the following is a correct pairing of a virus family and a disease it causes?

Accepted Answer

Flaviviridae – Yellow fever

Question 15

Which of the following statements about the oncogene theory and viral involvement in cancer is correct?

Accepted Answer

Multiple 'hits' or mutations, including those caused by viruses, are required to activate oncogenes and cause cancer.

Question 16

Which of the following best describes the replication strategy of a double-stranded RNA (dsRNA) virus in a host cell?

Accepted Answer

The positive strand acts as mRNA, while each strand serves as a template for synthesis of its complement.

Question 17

Which of the following is a plausible reason why prion diseases are difficult to treat and control?

Accepted Answer

Prions lack nucleic acids and are resistant to most sterilization methods.

Question 18

Which of the following best explains the difference between a latent animal virus and a lysogenic bacteriophage?

Accepted Answer

Lysogenic phages can be induced to enter the lytic cycle, while latent animal viruses may remain permanently in the host genome.

Characterizing and Classifying Viruses, Viroids, and Prions

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