Question 1

A virus consisting of a single strand of RNA, which is reverse transcribed into complementary DNA, is referred to as a ________.

Accepted Answer

A)  protease 
B)  retrovirus 
C)  bacteriophage 
D)  non-enveloped virus 
A)  protease 
B)  retrovirus 
C)  bacteriophage 
D)  non-enveloped virus

Question 2

Use the figures to answer the question.
 
Which of the three types of viruses shown would you expect to include glycoproteins?

Accepted Answer

A)  I only 
B)  II only 
C)  III only 
D)  I and II only 
A)  I only 
B)  II only 
C)  III only 
D)  I and II only

Question 3

Which of the following statements is correct regarding viral infections in plants?

Accepted Answer

A)  They can be controlled with antibiotics. 
B)  They can spread within a plant via plasmodesmata. 
C)  They have little effect on plant growth. 
D)  They are not spread by animals. 
A)  They can be controlled with antibiotics. 
B)  They can spread within a plant via plasmodesmata. 
C)  They have little effect on plant growth. 
D)  They are not spread by animals.

Question 4

Use the following figure and information to answer the question.
 
Cells were infected with approximately 1,000 copies of either virus A or virus B at the 0 time point. At five-minute intervals, a sample of the virus and cell mixture was removed. The intact cells were removed from the sample, and the number of viruses per milliliter of culture was determined.
Using the data in the figure, how long does it take for virus B to go through one lytic cycle?

Accepted Answer

A)  15 minutes 
B)  30 minutes 
C)  45 minutes 
D)  60 minutes 
A)  15 minutes 
B)  30 minutes 
C)  45 minutes 
D)  60 minutes

Question 5

Use the following information to answer the question.
The herpesviruses are important enveloped DNA viruses that cause disease in vertebrates and in some invertebrates such as oysters. Some of the human forms are herpes simplex virus (HSV)types I and II, causing facial and genital lesions, and the varicella zoster virus (VSV), causing chicken pox and shingles. Each of these three actively infects nervous tissue. Primary infections are fairly mild, but the virus is not then cleared from the host; rather, viral genomes are maintained in cells in a latent phase. The virus can later reactivate, replicate again, and infect others.
In electron micrographs of HSV infection, it can be seen that the intact virus initially reacts with cell-surface proteoglycans, then with specific receptors. This is later followed by viral capsids docking with nuclear pores. Afterward, the capsids go from being full to being "empty." Which of the following statements best fits these observations?

Accepted Answer

A)  Viral capsids are needed for the cell to become infected; only the capsids enter the nucleus. 
B)  The viral envelope is not required for infectivity, since the envelope does not enter the nucleus. 
C)  Only the genetic material of the virus is involved in the cell's infectivity, and is injected like the genome of a phage. 
D)  The viral envelope mediates entry into the cell, the capsid mediates entry into the nuclear membrane, and the genome is all that enters the nucleus. 
A)  Viral capsids are needed for the cell to become infected; only the capsids enter the nucleus. 
B)  The viral envelope is not required for infectivity, since the envelope does not enter the nucleus. 
C)  Only the genetic material of the virus is involved in the cell's infectivity, and is injected like the genome of a phage. 
D)  The viral envelope mediates entry into the cell, the capsid mediates entry into the nuclear membrane, and the genome is all that enters the nucleus.

Question 6

Why do scientists consider HIV to be an emerging virus?

Accepted Answer

A)  HIV infected humans long before the 1980s, but it has now mutated to a deadlier form. 
B)  HIV mutates rapidly, making the virus very different from HIV in the early 1980s. 
C)  HIV suddenly became apparent and widespread in the 1980s. 
D)  HIV is now starting to cause diseases other than AIDS, such as rare types of cancers and pneumonias. 
A)  HIV infected humans long before the 1980s, but it has now mutated to a deadlier form. 
B)  HIV mutates rapidly, making the virus very different from HIV in the early 1980s. 
C)  HIV suddenly became apparent and widespread in the 1980s. 
D)  HIV is now starting to cause diseases other than AIDS, such as rare types of cancers and pneumonias.

Question 7

Which of the following statements correctly describes a difference between viruses and prions?

Accepted Answer

A)  Viruses infect many types of cells, whereas prions infect only prokaryotic cells. 
B)  Viruses have capsids composed of protein, whereas prions are made only of nucleic acid. 
C)  Viruses have genomes composed of RNA, whereas prions have genomes composed of DNA. 
D)  Viruses generally cause disease symptoms quickly, whereas prions generally take many years to cause disease symptoms. 
A)  Viruses infect many types of cells, whereas prions infect only prokaryotic cells. 
B)  Viruses have capsids composed of protein, whereas prions are made only of nucleic acid. 
C)  Viruses have genomes composed of RNA, whereas prions have genomes composed of DNA. 
D)  Viruses generally cause disease symptoms quickly, whereas prions generally take many years to cause disease symptoms.

Question 8

A researcher lyses a cell that contains nucleic acid molecules and capsomeres of tobacco mosaic virus (TMV). The cell contents are left in a covered test tube overnight. The next day this mixture is sprayed on tobacco plants. What would you expect to happen to the plants that were sprayed with the mixture?

Accepted Answer

A)  The plants would develop some but not all of the symptoms of the TMV infection. 
B)  The plants would develop the typical symptoms of TMV infection. 
C)  The plants would not show any disease symptoms. 
D)  The plants would become infected, but extracts from these plants would be unable to infect other plants. 
A)  The plants would develop some but not all of the symptoms of the TMV infection. 
B)  The plants would develop the typical symptoms of TMV infection. 
C)  The plants would not show any disease symptoms. 
D)  The plants would become infected, but extracts from these plants would be unable to infect other plants.

Question 9

Which of the following processes within viral replication is the greatest source of genetic variation in RNA virus populations?

Accepted Answer

A)  High mutation rate due to lack of proofreading of RNA genome replication errors. 
B)  Transcription from the host cell RNA polymerase introduces numerous mutations. 
C)  Capsid proteins from the host cell can replace the viral capsid. 
D)  Viral RNA is translated by host cell ribosomes. 
A)  High mutation rate due to lack of proofreading of RNA genome replication errors. 
B)  Transcription from the host cell RNA polymerase introduces numerous mutations. 
C)  Capsid proteins from the host cell can replace the viral capsid. 
D)  Viral RNA is translated by host cell ribosomes.

Question 10

The virus genome and viral proteins are assembled into virus particles during which of the following parts of the reproductive cycle?

Accepted Answer

A)  the lytic cycle and the lysogenic cycle in all known host organisms 
B)  the lysogenic cycle only 
C)  the lytic cycle only 
D)  the lytic cycle in all host organisms but the lysogenic cycle only in bacteria 
A)  the lytic cycle and the lysogenic cycle in all known host organisms 
B)  the lysogenic cycle only 
C)  the lytic cycle only 
D)  the lytic cycle in all host organisms but the lysogenic cycle only in bacteria

Question 11

What is the function of reverse transcriptase in retroviruses?

Accepted Answer

A)  It uses viral RNA as a template for DNA synthesis. 
B)  It converts host cell RNA into viral DNA. 
C)  It translates viral RNA into proteins. 
D)  It uses viral RNA as a template for making complementary RNA strands. 
A)  It uses viral RNA as a template for DNA synthesis. 
B)  It converts host cell RNA into viral DNA. 
C)  It translates viral RNA into proteins. 
D)  It uses viral RNA as a template for making complementary RNA strands.

Question 12

The first class of antiviral drugs developed to treat HIV infection, such as AZT, were known as reverse transcriptase inhibitors. How did these drugs carry out their functions?

Accepted Answer

A)  The drugs targeted and destroyed the viral genome before it could be reverse transcribed into DNA. 
B)  The drug molecules bonded to the dsDNA genome of the virus in such a way that it could not separate for replication to occur. 
C)  The drug molecules bonded to the viral reverse transcriptase enzyme, thus preventing the virus from making a DNA copy of its RNA genome. 
D)  The drugs prevented host cells from producing the enzymes used by the virus to replicate its genome. 
A)  The drugs targeted and destroyed the viral genome before it could be reverse transcribed into DNA. 
B)  The drug molecules bonded to the dsDNA genome of the virus in such a way that it could not separate for replication to occur. 
C)  The drug molecules bonded to the viral reverse transcriptase enzyme, thus preventing the virus from making a DNA copy of its RNA genome. 
D)  The drugs prevented host cells from producing the enzymes used by the virus to replicate its genome.

Question 13

What are prions?

Accepted Answer

A)  mobile segments of DNA 
B)  tiny circular molecules of RNA that can infect plants 
C)  viral DNA that attaches itself to the host genome and causes disease 
D)  misfolded versions of normal proteins that can cause disease 
A)  mobile segments of DNA 
B)  tiny circular molecules of RNA that can infect plants 
C)  viral DNA that attaches itself to the host genome and causes disease 
D)  misfolded versions of normal proteins that can cause disease

Question 14

The difference between vertical and horizontal transmission of plant viruses is that vertical transmission is ________.

Accepted Answer

A)  transmission of a virus from a parent plant to its progeny, and horizontal transmission is one plant spreading the virus to another plant 
B)  the spread of viruses from upper leaves to lower leaves of the plant, and horizontal transmission is the spread of a virus among leaves at the same general level 
C)  the spread of viruses from trees and tall plants to bushes and other smaller plants, and horizontal transmission is the spread of viruses among plants of similar size 
D)  the transfer of DNA from a plant of one species to a plant of a different species, and horizontal transmission is the spread of viruses among plants of the same species 
A)  transmission of a virus from a parent plant to its progeny, and horizontal transmission is one plant spreading the virus to another plant 
B)  the spread of viruses from upper leaves to lower leaves of the plant, and horizontal transmission is the spread of a virus among leaves at the same general level 
C)  the spread of viruses from trees and tall plants to bushes and other smaller plants, and horizontal transmission is the spread of viruses among plants of similar size 
D)  the transfer of DNA from a plant of one species to a plant of a different species, and horizontal transmission is the spread of viruses among plants of the same species

Exam 19: Viruses

A virus consisting of a single strand of RNA, which is reverse transcribed into complementary DNA, is referred to as a ________.

Use the figures to answer the question. Which of the three types of viruses shown would you expect to include glycoproteins?

Which of the following statements is correct regarding viral infections in plants?

Why do scientists consider HIV to be an emerging virus?

Which of the following statements correctly describes a difference between viruses and prions?

Which of the following processes within viral replication is the greatest source of genetic variation in RNA virus populations?

The virus genome and viral proteins are assembled into virus particles during which of the following parts of the reproductive cycle?

What is the function of reverse transcriptase in retroviruses?

The first class of antiviral drugs developed to treat HIV infection, such as AZT, were known as reverse transcriptase inhibitors. How did these drugs carry out their functions?

What are prions?

The difference between vertical and horizontal transmission of plant viruses is that vertical transmission is ________.

Evolution, the Themes of Biology, and Scientific Inquiry

The Chemical Context of Life

Water and Life

Carbon and the Molecular Diversity of Life

The Structure and Function of Large Biological Molecules

A Tour of the Cell

Membrane Structure and Function

An Introduction to Metabolism

Cellular Respiration and Fermentation

Photosynthesis

Cell Communication

The Cell Cycle

Meiosis and Sexual Life Cycles

Mendel and the Gene Idea

The Chromosomal Basis of Inheritance

The Molecular Basis of Inheritance

Gene Expression: From Gene to Protein

Regulation of Gene Expression

DNA Tools and Biotechnology

Genomes and Their Evolution

Descent with Modification: A Darwinian View of Life

The Evolution of Populations

The Origin of Species

The History of Life on Earth

Phylogeny and the Tree of Life

Bacteria and Archaea

Protists

Plant Diversity I: How Plants Colonized Land

Plant Diversity II: The Evolution of Seed Plants

Fungi

An Overview of Animal Diversity

An Introduction to Invertebrates

The Origin and Evolution of Vertebrates

Vascular Plant Structure, Growth, and Development

Resource Acquisition and Transport in Vascular Plants

Soil and Plant Nutrition

Angiosperm Reproduction and Biotechnology

Plant Responses to Internal and External Signals

Basic Principles of Animal Form and Function

Animal Nutrition

Circulation and Gas Exchange

The Immune System

Osmoregulation and Excretion

Hormones and the Endocrine System

Animal Reproduction

Animal Development

Neurons, Synapses, and Signaling

Nervous Systems

Sensory and Motor Mechanisms

Animal Behavior

An Introduction to Ecology and the Biosphere

Population Ecology

Community Ecology

Ecosystems and Restoration Ecology

Conservation Biology and Global Change

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