Deck 35: Viruses

Question 1

Which of the following statements applies to the lysogenic cycle?

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

Answer 1

C

Question 2

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?

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

Answer 2

A

Question 3

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

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

Answer 3

B

Question 4

You just discovered a new virus.This virus infects heart muscle,where it causes inflammation.This virus has a very high mutation rate.Which of the following is the best strategy for finding a treatment for this virus?

A)Develop a vaccine from living viruses.
B)Identify the receptor this virus uses and develop an antibody against that receptor.
C)Encourage infected individuals to engage in heart-strengthening exercise.
D)Develop a drug that blocks the host's ribosomes,which the virus uses to produce its proteins.

Question 5

You have been happily growing your bacterial cultures for many weeks.One day,you discover that one of your cultures has lysed.Which of the following experiments will indicate that a bacteriophage is responsible for the cell lysis?

A)You filter the lysed culture through a 0.3-micrometer filter and use the filtrate to infect more cells.After 45 minutes,the second bacterial culture lyses.
B)You examine the lysed culture using the electron microscope and discover you have many particles about 50-nanometer long,with a head,tail,and tail spikes.
C)You filter the lysed culture through a 0.3-micrometer filter and add fresh growth media.After 24 hours of incubation,the growth media is cloudy,like a bacterial culture.
D)A and B.
E)B and C.

Question 6

What is difference between an epidemic and a pandemic?

A)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.
B)An epidemic is an actual disease,whereas a pandemic is a worldwide human response to treating that disease.
C)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.
D)An epidemic is a disease with a fairly low mortality rate,whereas a pandemic has a much higher mortality rate.

Question 7

What is the main structural difference between enveloped and nonenveloped viruses?

A)Enveloped viruses have their genetic material enclosed by a protein or phospholipid coat.
B)Nonenveloped viruses have only a phospholipid membrane,while enveloped viruses have two membranes,the other one being a protein capsid.
C)Enveloped viruses have a phospholipid membrane outside their capsid,whereas nonenveloped viruses do not.
D)Both viruses have a capsid and phospholipid membrane,but,in the nonenveloped virus,the genetic material is between these two membranes,while in the enveloped virus the genetic material is inside both membranes.

Question 8

Figure 35.1
Using the data in Figure 35.1,how long does it take for virus B to go through one lytic cycle?

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

Question 9

The first class of drugs developed to treat AIDS-such as AZT-were known as reverse transcriptase inhibitors.What was the mechanism by which they worked to treat HIV infections?

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

Question 10

Figure 35.1
Cells were infected with approximately 1000 copies of either virus A or virus B at the 0 time point.At 5-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.

A)15 minutes
B)30 minutes
C)45 minutes
D)90 minutes

Question 11

Does treating a viral infection with antibiotics affect the course of the infection?

A)No;antibiotics do not kill viruses,because viruses use host proteins to replicate and antibiotics affect bacterial proteins.
B)No;antibiotics do not kill viruses,because viruses self-assemble into active particles.
C)Yes;antibiotics activate the immune system,and this decreases the severity of the infection.
D)Yes;antibiotics can prevent viral entry into the cell by binding to host-receptor proteins.

Question 12

If you were trying to create an attenuated virus in order to develop a vaccine,which of the following strategies might you use?

A)Isolate the virus and inject it directly into a person.
B)Isolate the virus,destroy it with UV light,and inject it into a person.
C)Isolate the virus,expose it to a culture of bovine cells for several generations,and inject the live virus into a person.
D)Use mechanical forces to break the virus into smaller pieces,then inject these pieces into a person.

Question 13

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?

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

Question 14

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?

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 15

In doing gene therapy,researchers frequently use attenuated viruses.The goal of gene therapy is to insert a normal copy of the mutated,disease-causing gene into the patient's genome,so that they will start producing normal protein.Which type of virus is suited to this application?

A)lytic viruses
B)lysogenic viruses
C)either lytic or lysogenic viruses

Question 16

To make a vaccine against the polio virus,researchers treated the polio virus with formaldehyde and used this preparation to inject people.This is an example of

A)an inactivated virus vaccine.
B)an attenuated virus vaccine.
C)a vaccine of isolated viral proteins.

Question 17

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

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

Question 18

What is a significant difference between lytic and lysogenic viral growth?

A)In lytic growth,there are no mature viruses produced.
B)In lysogenic growth,the viral genome gets incorporated into the host genome.
C)In lytic growth,the host cells are not destroyed.
D)In lysogenic growth,there is a continuous release of mature viral particles throughout the infection.

Question 19

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

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

Question 20

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

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 21

Which of the following is the most important reason that developing treatments and vaccines,as well as staging an effective immune response for HIV infections,has been so difficult compared with other viruses?

A)The virus evades the immune system and drugs by hiding inside cells of the immune system,such as helper T cells.
B)The virus has few,if any,replication-correcting enzymes,and consequently mutates at a high rate.
C)The virus has no recognizable antigens and,thus,cannot be identified easily by the host's immune system.
D)Researchers probably have not yet identified the actual cause of AIDS and,thus,cannot target their drug development accordingly.

Question 22

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?

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

Question 23

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

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

Question 24

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

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

Question 25

The European spruce sawflies pose a potential threat to spruce forests.In order for the Baculoviruses to kill the larva,which of the following must occur first?

A)The viral polyhedra,must be digested to release viral particles.
B)Viral polyhedra must fuse with intestinal cells.
C)Viral particles must enter into the host's nucleus for transcription and replication.
D)Viral particles must be digested by gut proteases.

Question 26

Which of the following plays an important role in the ability of an enveloped virus to fuse with the host cell?

A)Presence of antibodies on the host cell surface that recognize the virus.
B)Presence of the same phospholipid bilayer structure in both virus and host cell.
C)Presence of capsid protein shell on the outermost layer of the virus.
D)Answers A and B

Question 27

You have isolated the genome from a novel virus and would like to determine its composition.You have three tubes,each containing one of these substances: 1. a protein that degrades dsDNA (DNase,tube 1)
2) a protein that degrades ssRNA (RNase,tube 2)
3) a protein that degrades other proteins (protease,tube 3)
You add some of your novel genome to tubes 1,2,and 3.The genome is not degraded in tube 1,2,or 3.Based on your knowledge of genome types that have been found in viruses,what could the genome's composition be?

A)dsRNA
B)dsDNA that is resistant to DNase
C)ssDNA
D)It could be any of the above.

Question 28

The European spruce sawflies pose a potential threat to spruce forests.Baculoviruses have proven to be highly effective biological control agents against these sawflies.Why would pest managers prefer to use a baculovirus rather than a predator feeding on the pest?

A)The baculovirus particles are harmless to vertebrates.
B)Each type of baculovirus only kills a small number of host species.
C)The virus cannot replicate outside of a host cell.
D)All of the above are reasons a baculovirus would be preferred over a predator.

Question 29

You have isolated the genome from a novel virus and would like to determine its composition.You have three tubes,each containing one of these substances: 1. a protein that degrades dsDNA (DNase,tube 1)
2) a protein that degrades ssRNA (RNase,tube 2)
3) a protease that degrades viral proteins (tube 3)
You add some of your novel genome to tubes 1,2,and 3.The genome is degraded in tube 2,but not in tube 1 or tube 3.Based on your knowledge of genome types that have been found in viruses,what could the genome's composition be?

A)dsDNA
B)ssDNA
C)ssRNA
D)protein
E)None of the above seem likely.

Question 30

Which receptors for HIV would you expect to find on macrophages and T cells?

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

Question 31

To make a vaccine against mumps,measles,or rabies,which type of viruses would be useful?

A)dsDNA viruses
B)negative-sense ssRNA viruses
C)retroviruses
D)positive-sense ssRNA viruses
E)dsRNA viruses

Question 32

It is believed that HIV has passed from chimps to humans more than once.This is very telling since it suggests that animal-to-human viral transmissions may be more common than previously thought.What is the best evidence in support of the conclusion that HIV made the chimp-to-human leap more than once?

A)HIV has multiple strains,and the virus does not appear to be able to leap from humans back to chimps.
B)HIV has appeared on multiple continents.
C)Human-to-human transmission of HIV requires direct personal contact that simply could not have resulted in the widespread outbreak we see today.
D)Several species are known to have similar viruses resulting in immunodeficiency diseases.

Question 33

Why do scientists consider HIV to be an emerging virus?

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

Question 34

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

A)Retroviruses
B)Double-stranded DNA viruses
C)Double-stranded RNA viruses
D)Negative-sense single-stranded RNA viruses
E)Positive-sense single-stranded RNA viruses

Question 35

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?

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