Deck 19: Viruses

Question 1

What is the function of reverse transcriptase in retroviruses?

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

Answer 1

B

Question 2

Which of the following is characteristic of the lytic cycle?

A)Many bacterial cells containing viral DNA are produced.
B)Viral DNA is incorporated into the host genome.
C)The viral genome replicates without destroying the host.
D)A large number of phages are released at a time.
E)The virus-host relationship usually lasts for generations.

Answer 2

D

Question 3

Viral envelopes can best be analyzed with which of the following techniques?

A)transmission electron microscopy
B)antibodies against specific proteins not found in the host membranes
C)staining and visualization with the light microscope
D)use of plaque assays for quantitative measurement of viral titer
E)immunofluorescent tagging of capsid proteins

Answer 3

B

Question 4

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

A)vertical transmission is transmission of a virus from a parent plant to its progeny, and horizontal transmission is one plant spreading the virus to another plant.
B)vertical transmission is 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)vertical transmission is 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)vertical transmission is the transfer of DNA from one type of plant virus to another, and horizontal transmission is the exchange of DNA between two plant viruses of the same type.
E)vertical transmission is 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.

Question 5

Which viruses have single-stranded RNA that acts as a template for DNA synthesis?

A)lytic phages
B)proviruses
C)viroids
D)bacteriophages
E)retroviruses

Question 6

Which of the following is the best predictor of how much damage a virus causes?

A)ability of the infected cell to undergo normal cell division
B)ability of the infected cell to carry on translation
C)whether the infected cell produces viral protein
D)whether the viral mRNA can be transcribed
E)how much toxin the virus produces

Question 7

Antiviral drugs that have become useful are usually associated with which of the following properties?

A)ability to remove all viruses from the infected host
B)interference with viral replication
C)prevention of the host from becoming infected
D)removal of viral proteins
E)removal of viral mRNAs

Question 8

The host range of a virus is determined by

A)the enzymes carried by the virus.
B)whether its nucleic acid is DNA or RNA.
C)the proteins in the host's cytoplasm.
D)the enzymes produced by the virus before it infects the cell.
E)the proteins on its surface and that of the host.

Question 9

Which of the following describes plant virus infections?

A)They can be controlled by the use of antibiotics.
B)They are spread via the plasmodesmata.
C)They have little effect on plant growth.
D)They are seldom spread by insects.
E)They can never be passed vertically.

Question 10

Which of the following can be effective in preventing the onset of viral infection in humans?

A)taking vitamins
B)getting vaccinated
C)taking antibiotics
D)applying antiseptics
E)taking nucleoside analogues that inhibit transcription

Question 11

In many ways,the regulation of the genes of a particular group of viruses will be similar to the regulation of the host genes.Therefore,which of the following would you expect of the genes of the bacteriophage?

A)regulation via acetylation of histones
B)positive control mechanisms rather than negative
C)control of more than one gene in an operon
D)reliance on transcription activators
E)utilization of eukaryotic polymerases

Question 12

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.Which of the following would be expected to occur?

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

Question 13

What are prions?

A)mobile segments of DNA
B)tiny molecules of RNA that infect plants
C)viral DNA that has had to attach itself to the host genome
D)misfolded versions of normal brain protein
E)viruses that invade bacteria

Question 14

Which of the following accounts for someone who has had a herpesvirus-mediated cold sore or genital sore getting flare-ups for the rest of his or her life?

A)re-infection by a closely related herpesvirus of a different strain
B)re-infection by the same herpesvirus strain
C)co-infection with an unrelated virus that causes the same symptoms
D)copies of the herpesvirus genome permanently maintained in host nuclei
E)copies of the herpesvirus genome permanently maintained in host cell cytoplasm

Question 15

Which of the following viral features is most apt to correlate with the size of the genome?

A)size of the viral capsomeres
B)RNA versus DNA genome
C)double- versus single-strand genomes
D)size and shape of the capsid
E)glycoproteins of the envelope

Question 16

Which of the following series best reflects what we know about how the flu virus moves between species?

A)An avian flu virus undergoes several mutations and rearrangements such that it is able to be transmitted to other birds and then to humans.
B)The flu virus in a pig is mutated and replicated in alternate arrangements so that humans who eat the pig products can be infected.
C)A flu virus from a human epidemic or pandemic infects birds; the birds replicate the virus differently and then pass it back to humans.
D)An influenza virus gains new sequences of DNA from another virus, such as a herpesvirus; this enables it to be transmitted to a human host.
E)An animal such as a pig is infected with more than one virus, genetic recombination occurs, the new virus mutates and is passed to a new species such as a bird, the virus mutates and can be transmitted to humans.

Question 17

Which of the following represents a difference between viruses and viroids?

A)Viruses infect many types of cells, whereas viroids infect only prokaryotic cells.
B)Viruses have capsids composed of protein, whereas viroids have no capsids.
C)Viruses contain introns, whereas viroids have only exons.
D)Viruses always have genomes composed of DNA, whereas viroids always have genomes composed of RNA.
E)Viruses cannot pass through plasmodesmata, whereas viroids can.

Question 18

Most molecular biologists think that viruses originated from fragments of cellular nucleic acid.Which of the following observations supports this theory?

A)Viruses contain either DNA or RNA.
B)Viruses are enclosed in protein capsids rather than plasma membranes.
C)Viruses can reproduce only inside host cells.
D)Viruses can infect both prokaryotic and eukaryotic cells.
E)Viral genomes are usually similar to the genome of the host cell.

Question 19

Which of the following statements describes the lysogenic cycle of lambda (λ)phage?

A)After infection, the viral genes immediately turn the host cell into a lambda-producing factory, and the host cell then lyses.
B)Most of the prophage genes are activated by the product of a particular prophage gene.
C)The phage genome replicates along with the host genome.
D)Certain environmental triggers can cause the phage to exit the host genome, switching from the lytic to the lysogenic.
E)The phage DNA is incorporated by crossing over into any nonspecific site on the host cell's DNA.

Question 20

Why do RNA viruses appear to have higher rates of mutation?

A)RNA nucleotides are more unstable than DNA nucleotides.
B)Replication of their genomes does not involve proofreading.
C)RNA viruses replicate faster.
D)RNA viruses can incorporate a variety of nonstandard bases.
E)RNA viruses are more sensitive to mutagens.

Question 21

The country or region hit hardest during the outbreak of SARS in 2002-2003 was

A)Asia.
B)Canada.
C)the United States.
D)the UK.
E)Australia.

Question 22

Which of the following is the most probable fate of a newly emerging virus that causes high mortality in its host?

A)It is able to spread to a large number of new hosts quickly because the new hosts have no immunological memory of them.
B)The new virus replicates quickly and undergoes rapid adaptation to a series of divergent hosts.
C)A change in environmental conditions such as weather patterns quickly forces the new virus to invade new areas.
D)Sporadic outbreaks will be followed almost immediately by a widespread pandemic.
E)The newly emerging virus will die out rather quickly or will mutate to be far less lethal.

Question 23

Use the following information to answer the questions below.
Some viruses can be crystallized and their structures analyzed.One such virus is Desmodium,or yellow mottle virus,which infects beans.This is a member of the tymovirus group and has a single-stranded RNA genome of ~6300 nucleotides.Its virion is 25-30 nm in diameter,and is made up of 180 copies of a single capsid protein that self-associate to form each capsomere,which has icosahedral symmetry with 20 facets.
If this virus has capsomeres with 20 facets,how many proteins form each one?

A)1
B)5
C)~6
D)~20
E)~180

Question 24

What are examples of mobile genetic elements?

A)plasmids
B)transposons
C)viruses
D)viruses and transposons only
E)viruses, transposons and plasmids

Question 25

Use the following information to answer the questions below.
Some viruses can be crystallized and their structures analyzed.One such virus is Desmodium,or yellow mottle virus,which infects beans.This is a member of the tymovirus group and has a single-stranded RNA genome of ~6300 nucleotides.Its virion is 25-30 nm in diameter,and is made up of 180 copies of a single capsid protein that self-associate to form each capsomere,which has icosahedral symmetry with 20 facets.
In a cell-free system,what other components would you have to provide for this virus to express its genes?

A)ribosomes, tRNAs and amino acids
B)ribosomes, tRNAs, amino acids, and GTP
C)RNA nucleotides and GTP
D)RNA nucleotides, RNA polymerase, and GTP
E)bean cell enzymes

Question 26

The spread of viral disease in a human population occurs through which means?

A)mutation of existing viruses
B)transmission through travel and movement
C)handling animals that have viruses that jump the species barrier
D)not getting vaccinated against the virus
E)All of these examples can help spread a viral disease.

Question 27

Use the figure that follows to answer the questions below.

Which of the three types of viruses shown above would you expect to include glycoproteins?

A)I only
B)II only
C)III only
D)I and II only
E)all three

Question 28

Use the following information to answer the following questions.
In 1971,David Baltimore described a scheme for classifying viruses based on how the virus produces mRNA.
The table below shows the results of testing five viruses for nuclease specificity,the ability of the virus to act as an mRNA,and presence (+)or absence (-)of its own viral polymerase.

Based on the above table,which virus meets the Baltimore requirements for a retrovirus?

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

Question 29

Use the following information to answer the following questions.
In 1971,David Baltimore described a scheme for classifying viruses based on how the virus produces mRNA.
The table below shows the results of testing five viruses for nuclease specificity,the ability of the virus to act as an mRNA,and presence (+)or absence (-)of its own viral polymerase.

Given Baltimore's scheme,a positive sense single-stranded RNA virus such as the polio virus would be most closely related to which of the following?

A)T-series bacteriophages
B)retroviruses that require a DNA intermediate
C)single-stranded DNA viruses such as herpes viruses
D)nonenveloped double-stranded RNA viruses
E)linear double-stranded DNA viruses such as adenoviruses

Question 30

Use the following information to answer the next few questions.
Poliovirus is a positive-sense RNA virus of the picornavirus group.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 result in labelling of only very long proteins,while longer periods of labelling result in several different short polypeptides.
What part of the poliovirus would first interact with host cell ribosomes to mediate translation?

A)the poly-A tail
B)the leader sequence
C)the VPg protein
D)the AUG in the leader sequence
E)the AUG at the start of the coding sequence

Question 31

Use the following figure to answer the questions below.

In the figure,when new viruses are being assembled (IV),what mediates the assembly?

A)host cell chaperones
B)assembly proteins coded for by the host nucleus
C)assembly proteins coded for by the viral genes
D)viral RNA intermediates
E)Nothing; they self-assemble.

Question 32

Use the figure that follows to answer the questions below.

Which of the three types of viruses shown above would you expect to include a capsid(s)?

A)I only
B)II only
C)III only
D)I and II only
E)all three

Question 33

H1N1 was declared ________ in June 2009.

A)an epidemic
B)a pandemic
C)cured
D)under control
E)non-life-threatening

Question 34

Use the following information to answer the next few questions.
Poliovirus is a positive-sense RNA virus of the picornavirus group.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 result 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?

A)The host cell cannot translate viral protein with the amino acid analogues.
B)Host cell ribosomes only translate the viral code into short polypeptides.
C)The RNA is only translated into a single long polypeptide, which is then cleaved into shorter ones.
D)The RNA is translated into short polypeptides, which are subsequently assembled into large ones.
E)The large radioactive polypeptides are coded by the host, whereas the short ones are coded for by the virus.

Question 35

Use the following information to answer the following questions.
In 1971,David Baltimore described a scheme for classifying viruses based on how the virus produces mRNA.
The table below shows the results of testing five viruses for nuclease specificity,the ability of the virus to act as an mRNA,and presence (+)or absence (-)of its own viral polymerase.

Based on the above table,which virus meets the requirements for a bacteriophage?

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

Question 36

The SARS outbreak in 2003 resulted in ________ deaths in Canada.

A)8000
B)1026
C)438
D)44
E)none

Question 37

Viral disease in plants is spread through the population by

A)horizontal transmission (direct infection).
B)vertical transmission (one generation to the next).
C)horizontal and vertical transmission.
D)being in contact with animals harbouring viruses that can jump the species barrier.
E)There is no viral disease in plants as viruses only attack animals and bacteria.

Question 38

Use the following information to answer the questions below.
Some viruses can be crystallized and their structures analyzed.One such virus is Desmodium,or yellow mottle virus,which infects beans.This is a member of the tymovirus group and has a single-stranded RNA genome of ~6300 nucleotides.Its virion is 25-30 nm in diameter,and is made up of 180 copies of a single capsid protein that self-associate to form each capsomere,which has icosahedral symmetry with 20 facets.
If this virus has a positive RNA strand as its genome,it begins the infection by using this strand as mRNA.Therefore,which of the following do you expect to be able to measure?

A)replication rate
B)transcription rate
C)translation rate
D)accumulation of new ribosomes
E)formation of new transcription factors

Question 39

Use the following figure to answer the questions below.

In the figure,at the arrow marked II,what enzyme(s)are being utilized?

A)reverse transcriptase
B)viral DNA polymerase
C)host cell DNA polymerase
D)host cell RNA polymerase
E)host cell DNA and RNA polymerases

Question 40

Use the following information to answer the questions below.
Some viruses can be crystallized and their structures analyzed.One such virus is Desmodium,or yellow mottle virus,which infects beans.This is a member of the tymovirus group and has a single-stranded RNA genome of ~6300 nucleotides.Its virion is 25-30 nm in diameter,and is made up of 180 copies of a single capsid protein that self-associate to form each capsomere,which has icosahedral symmetry with 20 facets.
How many nucleotides of the genome would you expect to find in one capsid?

A)1
B)~6
C)~20
D)~180
E)~6300

Question 41

Emerging viruses arise by

A)mutation of existing viruses.
B)the spread of existing viruses to new host species.
C)the spread of existing viruses more widely within their host species.
D)mutation of existing viruses, the spread of existing viruses to new host species, and the spread of existing viruses more widely within their host species.
E)none of these.

Question 42

Why do scientists consider HIV to be an emerging virus?

A)HIV infected humans long before the 1980s, but it has now mutated to a more deadly 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.
E)To infect, HIV originally required other concurrent viral infections in the host, however, now HIV can infect humans in the absence of other concurrent viral infections.

Question 43

Which of the following characteristics,structures,or processes is common to both bacteria and viruses?

A)metabolism
B)ribosomes
C)genetic material composed of nucleic acid
D)cell division
E)independent existence

Question 44

Use the following information to answer the few questions.
The herpes viruses are very important enveloped DNA viruses that cause disease in all vertebrate species and in some invertebrates such as oysters.Some of the human ones are herpes simplex (HSV)I and II,causing facial and genital lesions,and the varicella-zoster (VSV),causing chicken pox and shingles.Each of these three actively infect 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 then reactivate,replicate again,and be infectious to others.
If scientists are trying to use what they know about HSV to devise a means of protecting other people from being infected,which of the following would have the best chance of lowering the number of new cases of infection?

A)vaccination of all persons with preexisting cases
B)interference with new viral replication in preexisting cases
C)treatment of the HSV lesions to shorten the breakout
D)medication that destroys surface HSV before it gets to neurons
E)education about avoiding sources of infection

Question 45

Which of the following viruses would most likely 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
E)both RNA- and DNA-based lytic viruses

Question 46

Use the following information to answer the few questions.
The herpes viruses are very important enveloped DNA viruses that cause disease in all vertebrate species and in some invertebrates such as oysters.Some of the human ones are herpes simplex (HSV)I and II,causing facial and genital lesions,and the varicella-zoster (VSV),causing chicken pox and shingles.Each of these three actively infect 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 then reactivate,replicate again,and be infectious to 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 best fits these observations?

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 entry into the nuclear membrane, and the genome is all that enters the nucleus.
E)The viral capsid mediates entry into the cell, and only the genomic DNA enters the nucleus, where it may or may not replicate.

Question 47

Use the following figure and information to answer the question(s)below.

Cells were infected with approximately 1000 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 above,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
E)It is not possible to determine.

Question 48

Refer to the treatments listed below to answer the following questions.
You isolate an infectious substance that is capable of causing disease in plants,but you do not know whether the infectious agent is a bacterium,virus,viroid,or prion.You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent.
I.treating the substance with nucleases that destroy all nucleic acids and then determining whether it is still infectious
II.filtering the substance to remove all elements smaller than what can be easily seen under a light microscope
III.culturing the substance by itself on nutritive medium,away from any plant cells
IV.treating the sample with proteases that digest all proteins and then determining whether it is still infectious
If you already knew that the infectious agent was either bacterial or viral,which treatment would allow you to distinguish between these two possibilities?

A)I
B)II
C)III
D)IV
E)either II or IV

Question 49

What is a population of viruses with similar characteristics called?

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

Question 50

Use the following information to answer the few questions.
The herpes viruses are very important enveloped DNA viruses that cause disease in all vertebrate species and in some invertebrates such as oysters.Some of the human ones are herpes simplex (HSV)I and II,causing facial and genital lesions,and the varicella-zoster (VSV),causing chicken pox and shingles.Each of these three actively infect 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 then reactivate,replicate again,and be infectious to others.
In 2009,a flu pandemic was believed to have originated when viral transmission occurred from pig to human,thereby earning the designation,"swine flu." Although pigs are thought to have been the breeding ground for the 2009 virus,sequences from bird,pig,and human viruses were all found within this newly identified virus when isolated from humans.What is the most likely explanation of why this virus contained sequences from bird,pig,and human viruses?

A)The virus was descended from a common ancestor of bird, pig, and human flu viruses.
B)The infected individuals happened to be infected with all three virus types.
C)Related viruses can undergo genetic recombination if the RNA genomes mix and match during viral assembly.
D)The human was likely infected with various bacterial strains that contained all three RNA viruses.
E)The swine virus genomic sequences evolved to be similar to bird and human.

Question 51

To cause a human pandemic,the H5N1 avian flu virus would have to

A)spread to primates such as chimpanzees.
B)develop into a virus with a different host range.
C)become capable of human-to-human transmission.
D)arise independently in chickens in North and South America.
E)become much more pathogenic.

Question 52

When is the virus genome and viral proteins assembled into virions?

A)During the lytic cycle and the lysogenic cycle in all known host organisms.
B)During the lysogenic cycle only.
C)During the lytic cycle only.
D)During the lytic cycle in eukaryotes and the lysogenic cycle only in prokaryotes.
E)During the lytic cycle in prokaryotes and the lysogenic cycle in eukaryoties.

Question 53

A bacterium is infected with an experimentally constructed bacteriophage composed of the T2 phage protein coat and T4 phage DNA.The new phages produced would have

A)T2 protein and T4 DNA.
B)T2 protein and T2 DNA.
C)a mixture of the DNA and proteins of both phages.
D)T4 protein and T4 DNA.
E)T4 protein and T2 DNA.

Question 54

Refer to the treatments listed below to answer the following questions.
You isolate an infectious substance that is capable of causing disease in plants,but you do not know whether the infectious agent is a bacterium,virus,viroid,or prion.You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent.
I.treating the substance with nucleases that destroy all nucleic acids and then determining whether it is still infectious
II.filtering the substance to remove all elements smaller than what can be easily seen under a light microscope
III.culturing the substance by itself on nutritive medium,away from any plant cells
IV.treating the sample with proteases that digest all proteins and then determining whether it is still infectious
Which treatment would you use to determine if the agent is a prion?

A)I only
B)II only
C)III only
D)IV only
E)either I or IV

Question 55

Use the following figure and information to answer the question(s)below.

Cells were infected with approximately 1000 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 above,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
E)It is not possible to determine.

Question 56

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

A)Enveloped viruses have their genetic material enclosed by a layer made only of protein.
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 have a phospholipid membrane.
D)Both types of 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.
E)Enveloped viruses are enclosed in a single phospholipid layer (not a bilayer), nonenveloped viruses do not have this envelope.

Question 57

RNA viruses require their own supply of certain enzymes because

A)host cells rapidly destroy the viruses.
B)host cells lack enzymes that can replicate the viral genome.
C)these enzymes translate viral mRNA into proteins.
D)these enzymes penetrate host cell membranes.
E)these enzymes cannot be made in host cells.

Question 58

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

A)They are not able to reproduce or carry out metabolism outside of a host cell.
B)Their DNA does not encode proteins.
C)They have RNA rather than DNA.
D)They do not evolve.
E)They mutate rapidly.

Question 59

Which of the following is true of viruses?

A)They manufacture their own ATP, proteins, and nucleic acids.
B)They use the host cell to copy themselves and make viral proteins.
C)They use the host cell to copy themselves and then viruses synthesize their own proteins.
D)They metabolize food and produce their own ATP.
E)They copy themselves but are unable to make proteins.

Question 60

Refer to the treatments listed below to answer the following questions.
You isolate an infectious substance that is capable of causing disease in plants,but you do not know whether the infectious agent is a bacterium,virus,viroid,or prion.You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent.
I.treating the substance with nucleases that destroy all nucleic acids and then determining whether it is still infectious
II.filtering the substance to remove all elements smaller than what can be easily seen under a light microscope
III.culturing the substance by itself on nutritive medium,away from any plant cells
IV.treating the sample with proteases that digest all proteins and then determining whether it is still infectious
Which treatment could definitively determine whether or not the component is a viroid?

A)I
B)II
C)III
D)IV
E)first II and then III

Question 61

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

A)ssRNA
B)dsRNA
C)ssDNA
D)dsDNA
E)both dsDNA and dsRNA

Question 62

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 would not be glycosylated and might not arrive at the host plasma membrane.
B)The viral capsid proteins would not be glycosylated and might not arrive at the host plasma membrane.
C)The viral core proteins would not be glycosylated and might not arrive at the host plasma membrane.
D)The virus would be unable to reproduce within the host cell.
E)There would be no impact on the virus.

Question 63

The first class of drugs developed to treat AIDS,such as AZT,were known as reverse transcriptase inhibitors.Why did they work?

A)AZT targets and destroys the viral genome before it can be reverse transcribed into DNA.
B)AZT interacts with the dsDNA genome of the virus in such a way that replication cannot occur.
C)AZT interacts with viral reverse transcriptase enzyme, thus preventing the virus from making a DNA copy of its RNA genome.
D)AZT prevents host cells from producing the enzymes used by the virus to replicate its genome.
E)AZT inhibits the virus from binding to host cells.

Question 64

Evidence suggests that factors which contribute towards the virulence of E.coli strain O157:H7,a bacterial strain reported to cause 2,100 hospitalizations in the US annually,are caused by genes from a virus that infects bacteria.Considering this evidence,which statement most likely explains how the O157:H7 population acquired the genetic variation that distinguishes the strain from harmless E.coli strains,such as those that reside in our intestines?

A)The virus entered the bacterial cell allowing the bacteria's cellular machinery to create new viruses.
B)Viral envelope proteins bind to receptors on the bacterial membrane, allowing the viral genetic material to enter the bacterium and become translated into proteins.
C)The virus entered the cell and acquired specific genes from the bacteria to increase the virulence of the virus.
D)The virus infected the bacterium, and allowed the bacterial population to replicate with a copy of the phage genome in each new bacterium.
E)The virus entered the cell and resulted in mutation of bacterial genes.

Question 65

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)Ebola

Question 66

What is difference between an epidemic and a pandemic?

A)An epidemic is a disease; a pandemic is a treatment.
B)An epidemic is restricted to a local region; a pandemic is global.
C)An epidemic has low mortality; a pandemic has higher mortality.
D)An epidemic is caused by a bacterial infection; a pandemic is caused by a viral infection.
E)An epidemic spreads more quickly than a pandemic.

Question 67

How can viruses infecting humans ensure their replication,when the human cells cannot perform the replication the viruses require?

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 viral genome codes for specialized enzymes not in the host.
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)The viruses stay in the lysogenic cycle until a new host becomes available.

Question 68

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

A)No; antibiotics work by inhibiting enzymes specific to bacteria.
B)No; antibiotics do not kill viruses because viruses do not have DNA.
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.
E)Yes; antibiotics prevent viral replication.

Question 69

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

A)HIV can be transmitted more easily from person to person than the flu virus.
B)The flu virus can be transmitted more easily from person to person than HIV.
C)This property of HIV makes it more likely to be a pandemic than the flu virus.
D)Disinfecting surfaces is more important to reduce the spread of HIV than the flu.
E)This results in HIVs more serious long-term consequences to the host.

Question 70

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)positive-sense ssRNA viruses
D)dsRNA viruses
E)ssDNA viruses

Question 71

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

A)The 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.
E)Recombination between viral and host DNA.