Deck 35: Viruses

Question 1

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.

Answer 1

C

Question 2

A biologist develops a new drug that seems to dramatically slow the onset of symptoms resulting from HIV infection.Close monitoring of HIV-infected cells reveals that the viral proteins are in the form of long polyproteins.What kind of drug did the biologist develop?

A)It is a reverse transcriptase inhibitor.
B)It is a CD4 inhibitor.
C)It is a protease inhibitor.
D)It is a polymerase inhibitor.

Answer 2

C

Question 3

A virus that has a single strand of RNA which it transcribes into complementary DNA is a _____.

A)reverse transcriptase
B)protease
C)retrovirus
D)RNA replicase virus
E)nonenveloped virus

Answer 3

C

Question 4

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)the HIV protease is easily precipitated out of the cell by combining with certain salt solutions.The HIV protease cleaves at specific places in viral polypeptides,which results in the formation of active viral proteins
E)the HIV protease cleaves at specific places in viral polypeptides,which results in the formation of active viral proteins.These drugs are very specific to the active site of the HIV protease

Question 5

Figure 35.2

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.
Using the data in Figure 35.2,how long does it take for virus A to go through one lytic cycle?

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

Question 6

What is difference between an epidemic and a pandemic?

A)An epidemic is a disease that spreads or becomes more common;a pandemic is a disease that remains stable in terms of numbers affected.
B)An epidemic is a disease;a pandemic is a treatment.
C)An epidemic is restricted to a local region;a pandemic is more global.
D)An epidemic is a disease with fairly low mortality;a pandemic has a much higher mortality rate.
E)An epidemic is caused by a bacterial infection;a pandemic is caused by a viral infection.

Question 7

Will 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 8

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.

Question 9

Figure 35.1

Seroconversion occurs when a person's immune system begins to manufacture antibodies against the HIV virus.Where on the graph in Figure 35.1 does seroconversion occur?

A)point B
B)point A
C)point C
D)point D
E)point E

Question 10

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 enzyme that blocks the 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 11

When people die from HIV infections,it is usually because _____.

A)they have too many HIV particles in their lymphatic system,which causes it to shut down
B)they have too few T cells to adequately fight infection
C)they have too many T cells,and this overwhelms their immune systems
D)the body diverts too much energy toward replenishing lost T cells
E)the virions (virus particles)destroy the host cells;as the number of virions increases the host loses too many cells to survive

Question 12

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 13

Which of the following supports the argument that viruses are nonliving?

A)They lack genetic material.
B)They are not cellular.
C)Their DNA does not encode proteins.
D)They have RNA rather than DNA.
E)They don't evolve.

Question 14

Figure 35.2

Using the data in Figure 35.2,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 15

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)The virus would be unable to reproduce within the host cell.

Question 16

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 17

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)HIV can be transmitted from person to person by sexual contact or injection of infected blood products;the flu virus can be transmitted from person to person by contact with a contaminated surface.
E)HIV can be transmitted from person to person by sexual contact or injection of infected blood products;the flu virus can be transmitted from person to person by contact with a contaminated surface as well as by direct physical contact.

Question 18

The virus genome and viral proteins are assembled into virions during _____.

A)both the lytic cycle and the lysogenic cycle in all 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 19

Viruses _____.

A)manufacture their own ATP and carbon-containing compounds like proteins and nucleic acids in order to survive
B)use the host cell's machinery to make more copies of themselves and to make viral proteins
C)need the host cell's machinery to make more copies of themselves before they can synthesize their own proteins
D)cannot reproduce or synthesize cell products without the host cell's machinery,but once their proteins are produced they are capable of metabolizing food to produce ATP
E)use their own protein-synthesizing machinery to make more viral proteins that are used to assemble more copies of themselves

Question 20

What would the result be if a drug that blocks the action of polymerase was introduced into a virus-infected organism?

A)The virus would not be able to enter new host cells.
B)The viral proteins would not be made and the virus would not be able to reproduce.
C)The newly formed virions would be unable to leave the host cell.
D)Viral proteins and viral DNA particles would not be able to be assembled.

Question 21

You isolate a cell infected with an adenovirus.What must you see when you examine the cell?

A)It is a bacterium.
B)It is undergoing mitosis.
C)Reverse transcriptase is present in the nucleus.
D)It does not have a nucleus.

Question 22

Mimivirus contains some of the genes required for protein synthesis.This is cited as support for which hypothesis about the origins of viruses?

A)degeneration
B)origin of life
C)escaped-genes
D)transposable elements

Question 23

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 24

Which of the following human diseases is caused by a virus that requires reverse transcriptase to transcribe its genome inside the host cell?

A)herpes
B)AIDS
C)smallpox
D)influenza
E)common cold

Question 25

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 26

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.

Question 27

You believe that you have isolated a new strain of positive-sense,single-stranded RNA virus and set about studying it in your laboratory.Which of the following lines of evidence would most strongly support your hypothesis that the virus is a [+]ssRNA?

A)The virions are diploid.
B)You sequence the bases in both the viral RNA and the mRNA and find them to be antiparallel.
C)Introducing a protease inhibitor causes the virus to stop producing proteins and reproducing.
D)Introducing a reverse transcriptase inhibitor slows down the growth of the virus.

Question 28

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 29

A population of viruses with similar characteristics is called a _____.

A)strain
B)species
C)type
D)genome
E)sense

Question 30

Which of the following could use reverse transcriptase to transcribe its genome?

A)ssRNA
B)dsRNA
C)ssDNA
D)dsDNA

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