Question 1

Which of the following is a reason why viruses are considered non- living?

Accepted Answer

A)  They contain different nucleotides in their DNA and RNA. 
B)  They do not have ribosomes or tRNAs. 
C)  They are surrounded by polysaccharides. 
D)  They do not contain a nuclear membrane. 
A)  They contain different nucleotides in their DNA and RNA. 
B)  They do not have ribosomes or tRNAs. 
C)  They are surrounded by polysaccharides. 
D)  They do not contain a nuclear membrane. B

Question 2

Use the following information when answering the corresponding questions).
It has been shown that there are two distinct variants of the HIV virus Bleul et al. 1997. The HIV coreceptors CXCR4 and CCR differentially regulated on human T- lymphocytes. Proceedings of the National Academy of Science 94:1925- 30). One virus preferentially infects macrophages and is called M- tropic. The other preferentially infects T cells and is called T- tropic. The M- tropic viruses use CCR5 and CD4 as coreceptors, and the T- tropic viruses use CXCR4 and CD4 as coreceptors. The
M- tropic viruses are found early in HIV infections; the T- tropic viruses are found late in infections, when AIDS symptoms are prevalent. T- tropic viruses are associated with a drastic decrease in T cells. Macrophages go to the site of wounds, where they are used to fight infections. T cells circulate in the body and fight infections at many sites.
-Which receptors for HIV would you expect to find on macrophages and T cells?

Accepted Answer

A)  CXCR4 and CD4 on macrophages; CCR5 and CD4 on T cells 
B)  CD4 and CXCR4 on macrophages; CXCR4 and CD4 on T cells 
C)  CCR5 and CD4 on macrophages; CXCR4 and CD4 on T cells 
D)  CCR5 and CXCR4 on macrophages; CD4 and CXCR4 on T cells 
A)  CXCR4 and CD4 on macrophages; CCR5 and CD4 on T cells 
B)  CD4 and CXCR4 on macrophages; CXCR4 and CD4 on T cells 
C)  CCR5 and CD4 on macrophages; CXCR4 and CD4 on T cells 
D)  CCR5 and CXCR4 on macrophages; CD4 and CXCR4 on T cells C

Question 3

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. We expect that the plants would

Accepted Answer

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

Question 4

You have isolated a newly discovered virus and are attempting to characterize it. You begin with its genome. You first isolate the virion- producing mRNA from culture cells infected with the virus. When you compare these mRNA with the viral genome, you find that they are complementary. What does this tell you?

Accepted Answer

A)  This virus has a negative- sense genome. 
B)  This virus has an ambisense genome. 
C)  The data are inconclusive. 
D)  This virus has a positive- sense genome. 
A)  This virus has a negative- sense genome. 
B)  This virus has an ambisense genome. 
C)  The data are inconclusive. 
D)  This virus has a positive- sense genome.

Question 5

When people die from HIV infections, it is usually because they

Accepted Answer

A)  divert too much energy toward replicating the virus. 
B)  have too many T cells, and this overwhelms their immune systems. 
C)  have too many HIV particles in their lymphatic system, which causes it to shut down. 
D)  have too few T cells to adequately fight infection. 
A)  divert too much energy toward replicating the virus. 
B)  have too many T cells, and this overwhelms their immune systems. 
C)  have too many HIV particles in their lymphatic system, which causes it to shut down. 
D)  have too few T cells to adequately fight infection.

Question 6

Viruses use the host's machinery to make copies of themselves. However, some human viruses require a type of replication that humans do not normally do. For example, humans normally do not have the ability to convert RNA into DNA. How can these types of viruses infect humans, when human cells cannot perform a particular role that the virus requires?

Accepted Answer

A)  Viruses can stay in a quiescent state until the host cell evolves this ability. 
B)  The virus infects only those cells and species that can perform all the replication roles necessary. 
C)  The virus causes mutations in the human cells, resulting in the formation of new enzymes that are capable of performing these roles. 
D)  The virus has in its own genome the code for any specialized enzymes that the host does not have. 
E)  All of the above have been frequently observed. 
A)  Viruses can stay in a quiescent state until the host cell evolves this ability. 
B)  The virus infects only those cells and species that can perform all the replication roles necessary. 
C)  The virus causes mutations in the human cells, resulting in the formation of new enzymes that are capable of performing these roles. 
D)  The virus has in its own genome the code for any specialized enzymes that the host does not have. 
E)  All of the above have been frequently observed.

Question 7

HIV is inactivated in the laboratory after a few minutes of sitting at room temperature; the flu virus is still active after sitting for several hours. What are the practical consequences of these findings?

Accepted Answer

A)  HIV can be transmitted from person to person by sexual contact or injection of infected blood products. 
B)  The flu virus can be transmitted from person to person by contact with a contaminated surface. 
C)  The flu virus can be transmitted from person to person by direct physical contact. 
D)  Both A and B apply. 
E)  All of the above answers apply. 
A)  HIV can be transmitted from person to person by sexual contact or injection of infected blood products. 
B)  The flu virus can be transmitted from person to person by contact with a contaminated surface. 
C)  The flu virus can be transmitted from person to person by direct physical contact. 
D)  Both A and B apply. 
E)  All of the above answers apply.

Question 8

As obligate intracellular parasites, viruses have which of these characteristics?

Accepted Answer

A)  After entering a cell, they use their own protein- synthesizing machinery to make more viral proteins that are used to assemble more copies of themselves. 
B)  After entering a cell, they use the host cell's machinery to make more copies of themselves using host proteins. 
C)  After entering a cell, they manufacture their own ATP and carbon- containing compounds, like proteins and nucleic acids, in order to survive. 
A)  After entering a cell, they use their own protein- synthesizing machinery to make more viral proteins that are used to assemble more copies of themselves. 
B)  After entering a cell, they use the host cell's machinery to make more copies of themselves using host proteins. 
C)  After entering a cell, they manufacture their own ATP and carbon- containing compounds, like proteins and nucleic acids, in order to survive.

Question 9

Figure 33.1
-Which of the following statements applies to lysogeny?

Accepted Answer

A)  Viral proteins are used to replicate the viral genome. 
B)  The viral genome integrates into the host cell's genome. 
C)  When the cell divides, the daughter cells are no longer infected. 
D)  Viral particles are produced continuously. 
A)  Viral proteins are used to replicate the viral genome. 
B)  The viral genome integrates into the host cell's genome. 
C)  When the cell divides, the daughter cells are no longer infected. 
D)  Viral particles are produced continuously.

Question 10

Figure 33.1
-Using the data in Figure 33.1, how long does it take for virus B to go through one lytic cycle?

Accepted Answer

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

Question 11

If a viral host cell has a mutation that interferes with the addition of carbohydrates to proteins in the Golgi, which of the following could likely result?

Accepted Answer

A)  The viral envelope proteins will not be glycosylated and may not arrive at the host plasma membrane. 
B)  The viral core proteins will not be glycosylated and may not arrive at the host plasma membrane. 
C)  The viral capsid proteins will not be glycosylated and may not arrive at the host plasma membrane. 
D)  None of the above will happen. 
A)  The viral envelope proteins will not be glycosylated and may not arrive at the host plasma membrane. 
B)  The viral core proteins will not be glycosylated and may not arrive at the host plasma membrane. 
C)  The viral capsid proteins will not be glycosylated and may not arrive at the host plasma membrane. 
D)  None of the above will happen.

Question 12

The HIV protease has been the target of several anti- HIV medications. This antiviral strategy is possible because

Accepted Answer

A)  the HIV protease is easily precipitated out of the cell by combining with certain salt solutions. 
B)  the HIV protease cleaves at specific places in viral polypeptides, which results in the formation of active viral proteins. 
C)  these drugs are very specific to the active site of the HIV protease. 
D)  both A and B apply. 
E)  both B and C apply. 
A)  the HIV protease is easily precipitated out of the cell by combining with certain salt solutions. 
B)  the HIV protease cleaves at specific places in viral polypeptides, which results in the formation of active viral proteins. 
C)  these drugs are very specific to the active site of the HIV protease. 
D)  both A and B apply. 
E)  both B and C apply.

Question 13

Which of the following viruses would have a disrupted replication cycle if their reverse- transcriptase enzyme was non- functional?

Accepted Answer

A)  double- stranded RNA viruses 
B)  retroviruses 
C)  positive- sense single- stranded RNA viruses 
D)  negative- sense single- stranded RNA viruses 
E)  double- stranded DNA viruses 
A)  double- stranded RNA viruses 
B)  retroviruses 
C)  positive- sense single- stranded RNA viruses 
D)  negative- sense single- stranded RNA viruses 
E)  double- stranded DNA viruses

Question 14

Use the following information when answering the corresponding questions).
It has been shown that there are two distinct variants of the HIV virus Bleul et al. 1997. The HIV coreceptors CXCR4 and CCR differentially regulated on human T- lymphocytes. Proceedings of the National Academy of Science 94:1925- 30). One virus preferentially infects macrophages and is called M- tropic. The other preferentially infects T cells and is called T- tropic. The M- tropic viruses use CCR5 and CD4 as coreceptors, and the T- tropic viruses use CXCR4 and CD4 as coreceptors. The
M- tropic viruses are found early in HIV infections; the T- tropic viruses are found late in infections, when AIDS symptoms are prevalent. T- tropic viruses are associated with a drastic decrease in T cells. Macrophages go to the site of wounds, where they are used to fight infections. T cells circulate in the body and fight infections at many sites.
-Poliovirus is an RNA virus of the picornavirus group, which uses its RNA as mRNA. At its 5' end, the RNA genome has a viral protein VPg) instead of a 5' cap. This is followed by a nontranslated leader sequence, and then a single long protein- coding region ~7000 nucleotides), followed by a poly- A tail. Observations were made that used radioactive amino acid analogues. Short- period use of the radioactive amino acids results in labelling of only very long proteins, while longer periods of labelling result in several different short polypeptides. What conclusion is most consistent with the results of the radioactive labelling experiment?

Accepted Answer

A)  The RNA is translated into short polypeptides, which are subsequently assembled into large ones. 
B)  The large radioactive polypeptides are coded by the host, whereas the short ones are coded for by the virus. 
C)  The RNA is only translated into a single long polypeptide, which is then cleaved into shorter ones. 
D)  Host- cell ribosomes only translate the viral code into short polypeptides. 
A)  The RNA is translated into short polypeptides, which are subsequently assembled into large ones. 
B)  The large radioactive polypeptides are coded by the host, whereas the short ones are coded for by the virus. 
C)  The RNA is only translated into a single long polypeptide, which is then cleaved into shorter ones. 
D)  Host- cell ribosomes only translate the viral code into short polypeptides.

Question 15

Which of the following viruses would be the most likely to have reverse transcriptase?

Accepted Answer

A)  a DNA- based lysogenic virus 
B)  an RNA- based lysogenic virus 
C)  an RNA- based lytic virus 
D)  a DNA- based lytic virus 
A)  a DNA- based lysogenic virus 
B)  an RNA- based lysogenic virus 
C)  an RNA- based lytic virus 
D)  a DNA- based lytic virus

Question 16

What is difference between an epidemic and a pandemic?

Accepted Answer

A)  An epidemic is an actual disease, whereas a pandemic is a worldwide human response to treating that disease. 
B)  An epidemic is a disease with a fairly low mortality rate, whereas a pandemic has a much higher mortality rate. 
C)  An epidemic is a disease that is restricted to a small area and does not appear to be spreading or becoming more common, whereas a pandemic is a disease that is spreading wider throughout a population. 
D)  An epidemic is a disease in a local region that is widening, whereas a pandemic is a disease that is widening to an international scale. 
A)  An epidemic is an actual disease, whereas a pandemic is a worldwide human response to treating that disease. 
B)  An epidemic is a disease with a fairly low mortality rate, whereas a pandemic has a much higher mortality rate. 
C)  An epidemic is a disease that is restricted to a small area and does not appear to be spreading or becoming more common, whereas a pandemic is a disease that is spreading wider throughout a population. 
D)  An epidemic is a disease in a local region that is widening, whereas a pandemic is a disease that is widening to an international scale.

Question 17

When HIV infects people, it does not immediately induce AIDS and kill its host. When people die from HIV infections, it is usually because

Accepted Answer

A)  the virus induces a coma and then eventually stops the heart muscle. 
B)  they have too many T cells, and this overwhelms their immune systems. 
C)  they have too many HIV particles in their lymph system, which causes it to shut down. 
D)  the virus starts destroying cells as it divides and causes massive internal hemorrhaging that leads to shock and eventually death. 
E)  they have too few T cells and become susceptible to secondary infections and cancers. 
A)  the virus induces a coma and then eventually stops the heart muscle. 
B)  they have too many T cells, and this overwhelms their immune systems. 
C)  they have too many HIV particles in their lymph system, which causes it to shut down. 
D)  the virus starts destroying cells as it divides and causes massive internal hemorrhaging that leads to shock and eventually death. 
E)  they have too few T cells and become susceptible to secondary infections and cancers.

Question 18

You are a physician, and you suspect your patient has a viral infection that has never been seen in humans. The infection is localized in the cells along the lining of the small intestine. The cells in this area are regularly sloughed off and replaced with new cells; that is, these cells are constantly dividing. When you isolate this new virus and incubate it in culture, you discover that it does not replicate well in cultures that have slowly dividing cells, but it does much more damage in cultures that have actively dividing cells. What do these findings suggest about this new virus?

Accepted Answer

A)  It is a double- stranded DNA virus. 
B)  It is a double- stranded RNA virus. 
C)  It is a negative- sense, single- stranded RNA virus. 
D)  It is a single- stranded DNA virus. 
A)  It is a double- stranded DNA virus. 
B)  It is a double- stranded RNA virus. 
C)  It is a negative- sense, single- stranded RNA virus. 
D)  It is a single- stranded DNA virus.

Question 19

Which of the following is true regarding the ambi- sense virus?

Accepted Answer

A)  The base sequences in the genome are complementary to those in viral mRNAs. 
B)  The genome contains the same sequences as the mRNA required to produce viral proteins. 
C)  Some sections of the genome are positive, while others are negative- sense. 
A)  The base sequences in the genome are complementary to those in viral mRNAs. 
B)  The genome contains the same sequences as the mRNA required to produce viral proteins. 
C)  Some sections of the genome are positive, while others are negative- sense.

Question 20

Why do scientists consider HIV to be an emerging virus?

Accepted Answer

A)  HIV mutates so rapidly that the virus of today has very little similarity to the virus in the first AIDS patients from the early 1980s. 
B)  HIV used to infect only chimps, but it has mutated in such a way that it now infects humans. 
C)  HIV is now starting to cause diseases other than AIDS, such as rare types of cancers and pneumonias. 
D)  HIV infected humans long before AIDS first become a problem in the early 1980s, but it has now mutated to a more deadly form. 
A)  HIV mutates so rapidly that the virus of today has very little similarity to the virus in the first AIDS patients from the early 1980s. 
B)  HIV used to infect only chimps, but it has mutated in such a way that it now infects humans. 
C)  HIV is now starting to cause diseases other than AIDS, such as rare types of cancers and pneumonias. 
D)  HIV infected humans long before AIDS first become a problem in the early 1980s, but it has now mutated to a more deadly form.

Exam 33: Viruses

Which of the following is a reason why viruses are considered non- living?

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. We expect that the plants would

When people die from HIV infections, it is usually because they

HIV is inactivated in the laboratory after a few minutes of sitting at room temperature; the flu virus is still active after sitting for several hours. What are the practical consequences of these findings?

As obligate intracellular parasites, viruses have which of these characteristics?

Figure 33.1 -Which of the following statements applies to lysogeny?

Figure 33.1 -Using the data in Figure 33.1, how long does it take for virus B to go through one lytic cycle?

If a viral host cell has a mutation that interferes with the addition of carbohydrates to proteins in the Golgi, which of the following could likely result?

The HIV protease has been the target of several anti- HIV medications. This antiviral strategy is possible because

Which of the following viruses would have a disrupted replication cycle if their reverse- transcriptase enzyme was non- functional?

Which of the following viruses would be the most likely to have reverse transcriptase?

What is difference between an epidemic and a pandemic?

When HIV infects people, it does not immediately induce AIDS and kill its host. When people die from HIV infections, it is usually because

Which of the following is true regarding the ambi- sense virus?

Why do scientists consider HIV to be an emerging virus?

Biology and the Tree of Life

Water and Carbon: the Chemical Basis of Life

Protein Structure and Function

Nucleic Acids and the Rna World

An Introduction to Carbohydrates

Lipids, Membranes, and the First Cells

Inside the Cell

Energy and Enzymes

Cellular Respiration and Fermentation

Photosynthesis

Cellcell Interactions

The Cell Cycle

Meiosis

Mendel and the Gene

Dna and the Gene: Synthesis and Repair

How Genes Work

Transcription, Rna Processing, and Translation

Control of Gene Expression in Bacteria

Control of Gene Expression in Eukaryotes

The Molecular Revolution: Biotechnology and Beyond

Gene Structure and Development

Evolution by Natural Selection

Evolutionary Processes

Speciation

Phylogenies and the History of Life

Bacteria and Archaea

Protists

Green Algae and Land Plants

Fungi

An Introduction to Animals

Protostome Animals

Deuterostome Animals

Plant Form and Function

Water and Sugar Transport in Plants

Plant Nutrition

Plant Sensory Systems, Signals, and Responses

Plant Reproduction and Development

Animal Form and Function

Water and Electrolyte Balance in Animals

Animal Nutrition

Gas Exchange and Circulation

Animal Nervous Systems

Animal Sensory Systems

Animal Movement

Chemical Signals in Animals

Animal Reproduction and Development

The Immune System in Animals

An Introduction to Ecology

Behavioural Ecology

Population Ecology

Community Ecology

Ecosystems and Global Ecology

Biodiversity and Conservation Biology

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