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Flashcards in Viruses [1] Deck (64):
1

Which of the following is NOT a way in which viruses are different from living organisms?
A: Viruses are acellular and all living things are made up of cells
B: Viruses are obligate parasites and no living organisms are obligate parasites.
C: Viruses depend on their host to synthesize the essential components of new viruses (e.g., genetic material and proteins), while living organisms are capable of synthesizing these components even if they require a host for food, shelter, or other necessities.
D: Viruses have DNA or RNA, not both

B

2

Which of the following groups contains some representatives with genomes that are so small that they may have as few as two genes?
Which of the following groups contains some representatives with genomes that are so small that they may have as few as two genes?
A: DNA viruses
B: bacteria
C: RNA viruses
D: eukaryotes

C

3

Some viruses have plus sense RNA genomes. Which of the following could describe one of those viruses?
A: a virus that has single-stranded DNA with the same nucleotide sequence as the functional mRNA that its host cell will translate to produce viral products
B: a virus that contains RNA with the complementary nucleotide sequence to the functional mRNA that its host cells will translate to produce viral products
C: a virus that has single-stranded DNA with the complementary nucleotide sequence to the functional mRNA that its host cell will translate to produce viral products
D: a virus that contains RNA with the same nucleotide sequence as the functional mRNA that its host cell will translate to produce viral products

D

4

Viral replication is
A: dependent on the host cell's DNA and RNA.
B: independent of both the host cell's DNA and the host cell's enzymes and metabolism.
C: dependent on the host cell's DNA, RNA, enzymes, and metabolism.
D: independent of the host cell's DNA but dependent on the host cell's enzymes and metabolism.

D

5

Which statement is TRUE?
Which statement is TRUE?
A: The origins of the nucleic acid polymerases used by viruses are eukaryotic.
B: All viruses contain their own nucleic acid polymerases.
C: Viruses do not contain their own nucleic acid polymerases.
D: Many viruses contain their own nucleic acid polymerases.

D

6

Reverse transcriptase is a(n)
A: RNA-dependent DNA polymerase.
B: DNA-dependent DNA polymerase.
C: RNA-dependent RNA polymerase.
D: DNA-dependent RNA polymerase.

A

7

ALL viral particles
A: exhibit cell lysis under a particular condition.
B: are smaller than bacterial cells.
C: contain an envelope to prevent its degradation outside of a host.
D: are metabolically inert.

D

8

The discovery of retroviruses changed our understanding of
A: gene structure and organization.
B: infectious particles.
C: the flow of genetic information.
D: protein synthesis.

C

9

Based on your knowledge of cellular and viral processes, which of the following would be (an) appropriate target(s) for antiviral drugs?
A: aminoacyl-tRNA synthetases
B: integrases
C: ribosomes
D: aminoacyl-tRNA synthetases and ribosomes

B

10

Which of the following enzymes would you expect to find in the virion of a retrovirus, but NOT in a bacteriophage?
A: reverse transcriptase
B: restriction enzymes
C: lysozyme
D: methylase

A

11

Retroviruses are medically important viruses because
A: they include the viruses the cause hepatitis.
B: some retroviruses cause cancer.
C: they include viruses that cause cancer and AIDS.
D: they include the virus that causes AIDS.

C

12

The primer for retrovirus reverse transcription is a specific
A: nuclear tDNA.
B: tRNA encoded by the virus.
C: tRNA encoded by the cell.
D: nuclear tRNA.

C

13

The term "phage" is generally reserved for the viruses that infect
A: multiple species.
B: bacteria.
C: plants.
D: animals.

B

14

For bacteriophages and animal viruses ________ is the step in the viral life cycle that determines host cell or tissue specificity.
A: penetration
B: attachment
C: assembly
D: synthesis

B

15

What are the consequences of a viral infection of an animal cell?
A: lysogeny followed by eventual lysis
B: rapid lysis or latent infections
C: Outcomes vary from rapid lysis to persistent infections, latent infections, or cancer.
D: lysis or lysogeny

C

16

In viruses, genetic information flows from ________ to ________.
A: nucleic acid / protein
B: DNA / protein
C: capsid / virion
D: RNA / virion

A

17

What are the minimal components needed for a virion?
A: capsid, genome, envelope
B: capsid
C: genome and envelope
D: capsid and genome

D

18

When describing the viral genome, which terms could be used?
A: ds RNA
B: ds DNA
C: ss DNA
D: All of the listed responses are correct.

D

19

Some viruses, especially animal viruses, have an envelope surrounding their nucleocapsid. This envelope may have viral proteins embedded in it. Why are the viral proteins more readily recognized and targeted by the immune system than the envelope?
A: The envelope is not capable of stimulating an immune response because of its makeup.
B: Viral proteins are highly immunogenic in order to facilitate uptake by host cells, while the envelope is not important in uptake by host cells.
C: Enveloped viruses are often coated with animal cell membrane as they leave the cell. This membrane is a major component of the viral envelope. The viral proteins are more readily recognized by the immune system, as they are more distinct from the materials normally found in and on the cells. However, the envelope can contain several types of viral components as well.
D:` Only proteins can stimulate the immune system, so the phospholipids and glycoproteins of the envelope are not immunogenic.

C

20

Viruses rely on the host cell machinery to make new viruses, but they sometimes provide their own enzymes (such as reverse transcriptase, which is an RNA-dependent DNA polymerase). Which of the following types of enzymes would a virus need to provide in order to replicate within a cell? In other words, which of these enzymes would not normally be found in a cell unless a virus provided it?
A: DNA-dependent RNA polymerases for RNA viruses
B: DNA-dependent RNA polymerases for DNA viruses
C: RNA replicases (RNA-dependent RNA polymerases) for RNA viruses
D: DNA-dependent DNA polymerases for DNA viruses

C

21

Viral size is generally measured in
A: picometers.
B: centimeters.
C: micrometers.
D: nanometers.

D

22

Enveloped viral membranes are generally ________ with associated virus-specific ________.
A: lipid bilayers / phospholipids
B: protein bilayers / lipids
C: glycolipid bilayers / phospholipids
D: lipid bilayers / glycoproteins

D

23

When packaged in the virion, the complete complex of nucleic acid and protein is known as the virus
A: nucleocapsid.
B: capsid.
C: concatemer.
D: envelope.

A

24

Which of the following are the hosts for most enveloped viruses?
A: Archaea
B: fungi
C: animals
D: Bacteria

C

25

The size and shape of viral particles is largely governed by the size and packaging of the viral
A: genome.
B: envelope.
C: enzymes.
D: prophage.

A

26

Regarding the viral membrane of an enveloped virus, the lipids are derived from the ________, and the proteins are encoded by ________.
A: host's cell membrane / viral genes
B: virion / viral genes
C: host's cell membrane / host's genes
D: virion / host's genes

A

27

Why does the structure of plant and bacterial cells illustrate the reason for having few enveloped viruses that infect these cells?
A: Plant and bacterial cells contain cell walls that prevent viral infection.
B: Plant and bacterial cells contain cell walls that prevent attachment of viruses.
C: Plant and bacterial cells contain cell walls that limit the virus from budding out and obtaining the envelope.
D: Plant and bacterial cells contain cell walls that prevent viruses from being released from the cell.

C

28

Viral replication occurs
A: both intracellularly and extracellularly.
B: extracellularly.
C: either intracellularly or extracellularly, depending on the virus involved.
D: intracellularly.

D

29

When a virus enters a host cell in which it can replicate, the process is called a(n)
A: prophage.
B: insertion.
C: excision.
D: infection.

D

30

A cell that allows the complete replication cycle of a virus to take place is said to be a
A: permissive host.
B: lytic cell.
C: dead cell.
D: viral cell.

A

31

In a natural population of diverse slow-growing prokaryotic cells, what type of viruses would you expect to be most common?
A: icosahedral viruses
B: enveloped viruses
C: lytic bacteriophages
D: temperate bacteriophages

C

32

The growth of viruses in a culture is described as a one-step growth curve, because
A: assembly and release actually occur in one step.
B: virion numbers show no increase during intracellular replication and can only be counted after the virions burst from the host cell.
C: there is only one step in the viral life cycle which leads to only one replicative cycle in a culture.
D: the eclipse phase prevents the plating and enumeration of virions although new virions are produced at a steady rate during the eclipse phase.

B

33

Which of the following are viable methods of release of newly assembled viral particles?
A: budding
B: lysogeny
C: lysis of host cell
D: budding or lysis of host cell

D

34

Plaque assays are often used to estimate the number of virions in a sample of a particular volume (the titer). The count is given as plaque-forming units. Which of the following is NOT generally a concern that must be considered in evaluating the results of plaque assays?
A: The plaques must be clearly visible in order to be counted accurately; this technique cannot be used with viruses that do not cause clear cellular damage.
B: The largest problem is that single viruses may create multiple plaques, resulting in overestimates of the number of viruses present.
C: The largest problem is that the count may underestimate the total number of viral particles, as not all virions may be able to cause infection.
D: The plaques must be at a density that can be counted on the plate; high and low densities may result in inaccurate counts.

B

35

Viruses infecting ________ are typically the easiest to grow in the laboratory.
A: animals
B: prokaryotes
C: fungi
D: plants

B

36

The use of ________ is the easiest and most effective way of studying many animal and plant viruses.
A: bacterial cultures
B: live hosts
C: tissue or cell culture
D: prophages

C

37

When solutions of host cells and infectious virions are mixed and spread on an agar plate, ________ form where viruses lyse the host cells.
A: colonies
B: prophages
C: plaques
D: insertion sequences

C

38

The concentration of infectious plaque forming units (pfu) per volume of fluid is known as the
A: virulence.
B: infectivity.
C: fluid infectivity.
D: titer.

D

39

When determining the number of bacterial virus particles in a suspension, why is the number obtained always less than the actual viral titer?
A: Because there may not be enough cells for each viral particle to infect.
B: Because it can be difficult to accurately count all of the plaques produced by infection.
C: Because all of the virus particles do not infect with 100% efficiency.
D: Because the cells used for culturing the virus may become resistant to the virus.

C

40

Cellular receptors may be composed of
A: combinations of proteins, carbohydrates, and/or lipids.
B: lipids.
C: carbohydrates.
D: proteins.

A

41

Bacteriophage have a ________ complex structure than animal viruses, because ________.
A: more / the bacteriophage must penetrate the peptidoglycan cell wall
B: less / there prokaryotic cells have a simple structure compared to eukaryotic cells
C: less / the bacteriophage does not have to penetrate the nucleus
D: more / bacteriophages must be coated by lipopolysaccharide to attach to bacterial cells

A

42

Virions infecting some bacteria possess the enzyme ________ that makes a small hole in the bacterial cell wall, allowing the viral nucleic acid to enter.
A: peptidoglycanase
B: lysozyme
C: nuclease
D: infectase

B

43

The packaging mechanism of T4 DNA involves cutting of DNA from
The packaging mechanism of T4 DNA involves cutting of DNA from
A: circular genetic elements.
B: linear genetic elements.
C: DNA concatemers.
D: its host cells.

C

*DNA concatemers are long linear strands of DNA with multiple copies of the original touching

44

T4 genes are transcribed by host RNA polymerase, yet the transcription of T4 genes is carefully
A: Rolling circle replication of the viral genome ensures that the genes are available for transcription in the correct order.
B: Each group of T4 genes has a different promoter that indicates that order in which they should be transcribed in based on the affinity of the promoter for the host RNA polymerase.
C: Early T4 genes encode for proteolytic enzymes that destroy the host RNA polymerase. Subsequently a viral polymerase is created that transcribes the middle and late genes in the correct order.
D: Early and middle T4 genes encode for proteins that modify the activity of sigma factors and host RNA polymerase to regulate the expression of T4 genes.

D

45

What would be the consequence of deleting the late T4 genes?
A: The T4 genome would not be copied.
B: ATP would not be produced and the T4 genome would not be packaged into the capsid.
C: T4 mRNA would not be produced.
D: T4 capsid proteins would not be made.

D

46

Viral structural proteins and proteins involved in the release of new viral particles that are synthesized after genomic replication begins would be considered
A: middle proteins
B: middle and late proteins
C: late proteins
D: early proteins

B

47

In which stage is the viral DNA introduced into the cell?
A: Release
B: Penetration
C: Attachment
D: Assembly
E: Biosynthesis

B

48

In which stage does formation of mature viruses occur?
A: Penetration
B: Release
C: Assembly
D: Attachment
E: Biosynthesis

C

49

The host DNA is usually degraded during which stage?
A: Release
B: Biosynthesis
C: Penetration
D: Assembly
E: Attachment

B

50

What would be the fate of a lytic bacteriophage if the host cell died prior to the assembly stage?
A: The cell could still be revived by the virus.
B: The virus would infect new hosts.
C: The virus would not be able to infect new hosts.

C

51

Which of the following examples is an example of lysogenic conversion?
A: T4 phages infect E. coli bacteria and are resistant to destruction by restriction enzymes.
B: Vibrio cholerae bacteria produce cholera toxin when infected with a phage.
C: An RNA virus infects a cell and causes the production of new viruses.
D: A lambda phage infects E. coli and enters the lytic cycle.

B

52

A virus that kills its host is said to be
A: temperate.
B: lytic or virulent.
C: virulent or lysogenic, but not temperate.
D: lysogenic.

B

53

A prophage replicates
A: independently of its host while the lytic genes are expressed.
B: along with its host while the lytic genes are not expressed.
C: along with its host while the lytic genes are expressed.
D: independently of its host while the lytic genes are not expressed.

B

54

The virus repressor protein
A: has different actions in different situations.
B: does not control the prophage's lytic genes but does control the incoming genomes of the same virus.
C: controls both the lytic genes on the prophage and prevents an incoming virus of the same type.
D: controls the prophage's lytic genes but not the incoming genomes of the same virus.

C

55

Which of the following statements is TRUE?
A: Lambda is a temperate phage that replicates its double-stranded DNA genome with a rolling circle mechanism.
B: Lambda is a temperate phage that infects Escherichia coli.
C: Lambda is a linear double-stranded DNA phage.
D: Lambda is replicated by the rolling circle mechanism.

A

56

Rolling circle replication of the lambda genome differs from replication of a bacterial chromosome in that
A: no concatamers are formed.
B: only a single strand of the genome is copied and no concatamers are formed.
C: only a single strand of the genome is copied.
D: bidirectional replication forks are not formed.

D

57

The consequence of an infection by a temperate bacteriophage is that the bacterial cell
A: lyses before it gets a chance to divide.
B: never lyses but continues to divide and replicate both the virus and the cell.
C: divides faster at moderate temperatures.
D: may lyse before it divides or may continue to divide and replicate both the virus and the cell.

D

58

You are attempting to mutate lambda to affect whether lysis or lysogeny occurs after lambda infection. Which mutation would INCREASE the chances of LYSOGENY over lysis?
A: overexpression of the cro gene
B: deletion or inactivation of the cro gene
C: deletion of both the cro and cI genes
D: deletion or inactivation of the cI gene

B

59

Whether lambda phage undergoes the lytic or lysogenic cycle is dependent on the accumulation of
A: viral genomes.
B: cI protein.
C: Cro protein.
D: methylated DNA.

B

60

What is the benefit, for a virus, to be a temperate or lysogenic virus?
A: A single infection event can produce millions of new viral particles instead of hundreds of viral particles.
B: A single infection event can produce hundreds of new viral particles.
C: A single infection even can allow other host cells to be infected by the same virus.
D: A single infection event can allow the virus to live in the host cell indefinitely.

A

61

Lysogenic viral DNA integrating into the host genome is referred to as
A: a prophage.
B: lysogeny.
C: lytic.
D: induction.

A

62

Which of the following events might trigger induction of a temperate bacteriophage?
A: Normal cell division of an infected cell
B: Exposure to UV light
C: Bacterial conjugation
D: An infected cell entering the logarithmic phase of growth

B

63

How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell?
A: The host cell dies during the lytic stage.
B: The host cell is allowed to live during the lytic stage.
C: The viral DNA may integrate into the host genome during the lytic stage.
D: The host cell can only divide during the lytic stage.

A

64

What is the fate of the prophage during the lysogenic stage?
A: It is released from the cell by lysing the cell.
B: It is degraded by the activity of host defense enzymes.
C: It is packaged into viral proteins and maintained until the host is exposed to an environmental stress.
D: It is copied every time the host DNA replicates.

D