Question 1

Which of the following best describes a virus?

Accepted Answer

A genetic element that can only multiply inside a living cell

Question 2

What is the main function of the capsid in a virus?

Accepted Answer

To surround and protect the viral genome

Question 3

Which of the following statements about viral genomes is correct?

Accepted Answer

Viral genomes can be either DNA or RNA, and may be linear or circular

Question 4

A virus particle (virion) is defined as:

Accepted Answer

The extracellular form of a virus that facilitates transmission between hosts

Question 5

Which symmetry is found in rod-shaped viruses such as tobacco mosaic virus?

Accepted Answer

Helical symmetry

Question 6

Enveloped viruses differ from naked viruses in that enveloped viruses:

Accepted Answer

Have a lipoprotein membrane surrounding the nucleocapsid

Question 7

Which enzyme is commonly found in bacteriophages and is critical for penetration of the host cell wall?

Accepted Answer

Lysozyme

Question 8

What is the role of neuraminidases in viral infection?

Accepted Answer

They cleave glycosidic bonds within connective tissue, allowing liberation of viruses from the cell

Question 9

Which of the following best describes the burst size in a viral replication cycle?

Accepted Answer

The number of virions released per cell

Question 10

During the latent period of a one-step viral growth curve, which events occur?

Accepted Answer

Eclipse and early maturation phases take place

Question 11

Which of the following is a critical requirement for the attachment of a virion to a host cell?

Accepted Answer

Presence of complementary receptors on the host cell surface

Question 12

Which of the following is NOT a typical receptor for bacteriophage attachment on bacterial cells?

Accepted Answer

Mitochondrial membrane

Question 13

What is the main difference between the virulent and temperate modes of bacteriophage life cycles?

Accepted Answer

Temperate mode allows replication of viral genome with host genome without killing the host

Question 14

Which process is used to measure the number of infectious virus particles in a sample?

Accepted Answer

Plaque assay

Question 15

A scientist observes clear zones on a lawn of host cells after adding a virus sample. What do these clear zones represent?

Accepted Answer

Plaques formed by lysis of host cells due to viral infection

Question 16

Which of the following best explains why animal viruses can be cultivated in tissue cultures?

Accepted Answer

Animal viruses replicate only in living cells, which can be provided by tissue cultures

Question 17

Which step in the bacteriophage T4 infection process involves the use of lysozyme?

Accepted Answer

Penetration of the host cell wall

Question 18

What is lysogenic conversion and why is it significant in pathogenic bacteria?

Accepted Answer

It is the acquisition of new properties by the host due to integration of viral genome, which can increase pathogenicity

Question 19

Which of the following statements about animal virus infection is correct?

Accepted Answer

The entire virion enters the animal cell, often by fusion or endocytosis

Question 20

A patient is infected with SARS-CoV-2. Which structural feature of the virus is responsible for binding to host cell receptors?

Accepted Answer

Spike (S) protein

5. Viruses: Structure, Life Cycle, and Infection

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