Question 1

Discuss at least six characteristics that are unique to viruses compared to other microorganisms.

Accepted Answer

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Question 2

Viral replication can involve the copying of RNA in an RNA virus.

Accepted Answer

RNA viruses replicate their RNA genome using viral RNA polymerase enzymes. The RNA acts as a template for the synthesis of complementary RNA strands and for the synthesis of viral proteins.

Question 3

Which type of virus is most likely to cause the immediate damage and destruction of an infected animal cell when it is released?
A) enveloped virus
B) RNA virus
C) nonenveloped virus
D) DNA virus

Accepted Answer

Nonenveloped viruses, also known as naked viruses, have a more resistant protein coat and are less susceptible to environmental changes than enveloped viruses. Therefore, they can cause immediate damage and destruction to the host cell upon release. In contrast, enveloped viruses have a lipid envelope that is easily disrupted by environmental factors, and RNA viruses tend to be less stable than DNA viruses.

Question 4

Discuss theories regarding the origins of viruses and make a case for whether viruses originated before cellular life-forms or after cellular life-forms.

Accepted Answer

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Question 5

Select the FALSE statement about viruses.
A) Cellular life-forms most likely preceded the origin of viruses since viruses need host cells in which to develop and reproduce.
B) Viruses are the most numerous microbes on Earth.
C) Viruses have impacted the evolution of all other cellular life-forms including bacteria, achaeans, and eukaryotes.
D) When viruses are treated in a way that prevents them from entering host cells and reproducing, they are said to be dead.

Accepted Answer

Viruses are not considered alive or dead as they do not have the ability to carry out metabolic processes on their own. They are simply considered inactive or active.

Question 6

Which of the following viral types enter animal cells via fusion with the animal cell membrane?
A) enveloped viruses
B) non enveloped viruses
C) naked viruses
D) All of these choices are correct.

Accepted Answer

Enveloped viruses have a phospholipid envelope that fuses with the host cell membrane during entry. Non-enveloped and naked viruses do not have such an envelope and rely on other mechanisms, such as receptor-mediated endocytosis, to enter the host cell.

Question 7

Compare and contrast viruses, prions, and viroids.

Accepted Answer

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Question 8

Compare and contrast the steps of viral multiplication cycles in bacteriophages and animal viruses.

Accepted Answer

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Question 9

A common method for cultivating viruses in the lab is to use in vitro systems called _____ cultures.

Accepted Answer

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Question 10

Noneveloped viruses enter their animal host cell via an active process that requires the participation of the animal cell.

Accepted Answer

Nonenveloped viruses do not have an outer membrane, so they require active participation from the host cell to enter. This is typically achieved through receptor-mediated endocytosis or membrane fusion. In contrast, enveloped viruses have a lipid membrane that can interact directly with the host cell membrane, allowing them to enter the cell without as much active participation from the host cell.

Question 11

Explain what is meant by host range, what governs host range, and what is meant by tissue tropism.

Accepted Answer

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Question 12

While of the following techniques or tools has provided information regarding the nature of viruses, which one had to be developed before the genetics, biochemistry, and life cycles of viruses could be thoroughly studied?
A) scanning electron microscopy
B) viral cultivation techniques
C) transmission electron microscopy
D) serological techniques

Accepted Answer

Before the genetics, biochemistry, and life cycles of viruses could be thoroughly studied, viral cultivation techniques had to be developed to grow and study viruses in the laboratory. This was essential for studying the nature of viruses, as it allowed for the isolation and manipulation of specific viral strains. Scanning and transmission electron microscopy and serological techniques provided additional information about the structure, composition, and behavior of viruses, but these techniques were dependent on first being able to grow and study viruses in the laboratory.

Question 13

Discuss why it is difficult to trace the origins of viruses and why they are important.

Accepted Answer

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Question 14

Discuss the criteria used for classifying viruses into families and genera.

Accepted Answer

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Question 15

During lysogeny, an inactive prophage state occurs when the viral DNA is inserted into the _________.

Accepted Answer

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Question 16

The descriptive groupings of virus into categories such as icosahedral and helical are based on
A) the type of nucleic acid.
B) the shape of the nucleocapsid.
C) the presence or absence of an envelope.
D) the mechanism of entry into host cells.

Accepted Answer

The descriptive groupings of virus into categories such as icosahedral and helical are based on the shape of the nucleocapsid. The nucleocapsid is the protein shell that encloses the viral genome, and it determines the overall shape of the virus. Therefore, the shape of the nucleocapsid is the basis for these descriptive categories.

Question 17

What tool or technique used by Ivanowski and Beijerinck while studying diseased tobacco plants enabled them to determine that the disease was caused by an agent significantly smaller than bacteria?
A) scanning electron microscopy that enabled them to view the virus the tobacco mosaic virus
B) transmission electron microscopy that allowed them to view the tobacco mosaic virus
C) porcelain filters that trapped bacteria but allowed passage of the virus
D) cell culture that enabled cultivation of the virus

Accepted Answer

Ivanowski and Beijerinck used porcelain filters that could trap bacteria but still allowed the disease-causing agent to pass through. This led them to conclude that the agent was significantly smaller than bacteria, suggesting that it was a virus.

Question 18

The three basic groups of viruses based on morphology include
A) enveloped viruses, non enveloped viruses, and complex viruses.
B) enveloped viruses, DNA viruses, and non enveloped viruses.
C) helical viruses, round viruses, and enveloped viruses.
D) non enveloped viruses, RNA viruses, and bacteriophages.

Accepted Answer

The three basic groups of viruses based on morphology are enveloped viruses, non enveloped viruses, and complex viruses. These groups are based on the presence or absence of an envelope and the complexity of their structure. DNA or RNA is not a distinguishing factor for the basic groups. Helical or round viruses are subtypes of non-enveloped or enveloped viruses, respectively, and are not basic groups. Bacteriophages are a type of virus that infects bacteria, but they are not a basic group based on morphology.

Quiz 6: An Introduction to Viruses

Discuss at least six characteristics that are unique to viruses compared to other microorganisms.

Viral replication can involve the copying of RNA in an RNA virus.

Which type of virus is most likely to cause the immediate damage and destruction of an infected animal cell when it is released?

Discuss theories regarding the origins of viruses and make a case for whether viruses originated before cellular life-forms or after cellular life-forms.

Select the FALSE statement about viruses.

Which of the following viral types enter animal cells via fusion with the animal cell membrane?

Compare and contrast viruses, prions, and viroids.

Compare and contrast the steps of viral multiplication cycles in bacteriophages and animal viruses.

A common method for cultivating viruses in the lab is to use in vitro systems called _____ cultures.

Noneveloped viruses enter their animal host cell via an active process that requires the participation of the animal cell.

Explain what is meant by host range, what governs host range, and what is meant by tissue tropism.

While of the following techniques or tools has provided information regarding the nature of viruses, which one had to be developed before the genetics, biochemistry, and life cycles of viruses could be thoroughly studied?

Discuss why it is difficult to trace the origins of viruses and why they are important.

Discuss the criteria used for classifying viruses into families and genera.

During lysogeny, an inactive prophage state occurs when the viral DNA is inserted into the _________.

The descriptive groupings of virus into categories such as icosahedral and helical are based on

What tool or technique used by Ivanowski and Beijerinck while studying diseased tobacco plants enabled them to determine that the disease was caused by an agent significantly smaller than bacteria?

The three basic groups of viruses based on morphology include