Deck 8: Viruses and Virology

Question 1

Enveloped viral membranes are generally ________ with associated virus-specific ________.

A)lipid bilayers / phospholipids
B)protein bilayers / lipids
C)lipid bilayers / glycoproteins
D)glycolipid bilayers / phospholipids

Answer 1

C

Question 2

A virus that kills its host is said to be

A)lytic or virulent.
B)temperate.
C)lysogenic.
D)virulent or lysogenic,but not temperate.

Answer 2

A

Question 3

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.

Answer 3

A

Question 4

Retroviruses are medically important viruses because

A)they include the viruses the cause hepatitis.
B)some retroviruses cause cancer.
C)they include the virus that causes AIDS.
D)they include viruses that cause cancer and AIDS.

Question 5

A prophage replicates

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

Question 6

Based on your knowledge of cellular and viral processes,which of the following would be (an)appropriate target(s)for antiviral drugs?

A)integrases
B)aminoacyl-tRNA synthetases
C)ribosomes
D)aminoacyl-tRNA synthetases and ribosomes

Question 7

Bacteriophages' genomes are typically composed of

A)single-stranded RNA.
B)single-stranded DNA.
C)double-stranded RNA.
D)double-stranded DNA.

Question 8

The virus repressor protein

A)controls the prophage's lytic genes but not the incoming genomes of the same virus.
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)has different actions in different situations.

Question 9

Viral replication occurs

A)intracellularly.
B)extracellularly.
C)both intracellularly and extracellularly.
D)either intracellularly or extracellularly,depending on the virus involved.

Question 10

Viral size is generally measured in

A)micrometers.
B)picometers.
C)nanometers.
D)centimeters.

Question 11

ALL viral particles

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

Question 12

The discovery of retroviruses changed our understanding of

A)gene structure and organization.
B)the flow of genetic information.
C)protein synthesis.
D)infectious particles.

Question 13

Which statement is TRUE?

A)All viruses contain their own nucleic acid polymerases.
B)Many viruses contain their own nucleic acid polymerases.
C)Viruses do not contain their own nucleic acid polymerases.
D)The origins of the nucleic acid polymerases used by viruses are eukaryotic.

Question 14

Which of the following statements is TRUE?

A)Lambda is a temperate phage that infects Escherichia coli.
B)Lambda is a linear double-stranded DNA phage.
C)Lambda is replicated by the rolling circle mechanism.
D)Lambda is a temperate phage that replicates its double-stranded DNA genome with a rolling circle mechanism.

Question 15

The packaging mechanism of T4 DNA involves cutting of DNA from

A)linear genetic elements.
B)circular genetic elements.
C)DNA concatemers.
D)its host cells.

Question 16

Which of the following enzymes would you expect to find in the virion of a retrovirus,but NOT in a bacteriophage?

A)lysozyme
B)methylase
C)restriction enzymes
D)reverse transcriptase

Question 17

Viral replication is

A)independent of the host cell's DNA but dependent on the host cell's enzymes and metabolism.
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 and RNA.
D)dependent on the host cell's DNA,RNA,enzymes,and metabolism.

Question 18

Viruses infecting ________ are typically the easiest to grow in the laboratory.

A)plants
B)animals
C)fungi
D)prokaryotes

Question 19

Restriction is

A)the viral process whereby a host's DNA ceases normal functioning.
B)the viral process whereby the virus prevents other viruses from entering the cell.
C)a general host mechanism to prevent the invasion of foreign nucleic acid.
D)a general host mechanism to prevent virus particles from further infective action.

Question 20

Cellular receptors may be composed of

A)proteins.
B)carbohydrates.
C)lipids.
D)combinations of proteins,carbohydrates,and/or lipids.

Question 21

The size and shape of viral particles is largely governed by the size and packaging of the viral

A)envelope.
B)enzymes.
C)prophage.
D)genome.

Question 22

Which of the following are the hosts for most enveloped viruses?

A)Bacteria
B)animals
C)Archaea
D)fungi

Question 23

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)infectase
C)lysozyme
D)nuclease

Question 24

Rolling circle replication of the lambda genome differs from replication of a bacterial chromosome in that

A)bidirectional replication forks are not formed.
B)only a single strand of the genome is copied.
C)no concatamers are formed.
D)only a single strand of the genome is copied and no concatamers are formed.

Question 25

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

Question 26

The primer for retrovirus reverse transcription is a specific

A)tRNA encoded by the cell.
B)tRNA encoded by the virus.
C)nuclear tRNA.
D)nuclear tDNA.

Question 27

When a virus enters a host cell in which it can replicate,the process is called a(n)

A)insertion.
B)infection.
C)prophage.
D)excision.

Question 28

Which of the following samples would contain the MOST genetic diversity?

A)viral metagenomes from the ocean
B)bacterial metagenomes from the ocean
C)microbial eukaryotic metagenomes from the ocean
D)viral metagenomes from human red blood cells

Question 29

Bacteriophage have a ________ complex structure than animal viruses,because ________.

A)more / bacteriophages must be coated by lipopolysaccharide to attach to bacterial cells
B)less / the bacteriophage does not have to penetrate the nucleus
C)more / the bacteriophage must penetrate the peptidoglycan cell wall
D)less / there prokaryotic cells have a simple structure compared to eukaryotic cells

Question 30

Viral proteins are categorized as early,middle,and late.Early proteins typically are necessary for

A)production of viral mRNA.
B)packaging of DNA into the nucleocapsid.
C)copying the viral genome.
D)production of viral mRNA and copying the viral genome.

Question 31

In E.coli,the adenine in the sequence GATC is methylated by the Dam enzyme.In the same cells a restriction endonuclease recognizes and cleaves dsDNA with GATC on either strand.Why does E.coli have these two enzymes?

A)The enzymes cut the E.coli genome into pieces that bind to viral particles and inhibit viral replication.
B)The enzymes increase the rate of mutation and genome rearrangement,thus increasing the likelihood that E.coli cells will mutate and become resistant to viral infection.
C)The enzymes encourage lysogeny because the cleavage sites are recognized by viral integrases.
D)The enzymes protect E.coli from infection by preferentially degrading viral or other exogenous DNA that is not methylated.

Question 32

T4 genes are transcribed by host RNA polymerase,yet the transcription of T4 genes is carefully controlled so that groups of T4 genes are transcribed at specific times after infection.How is this accomplished?

A)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.
B)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.
C)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.
D)Rolling circle replication of the viral genome ensures that the genes are available for transcription in the correct order.

Question 33

When solutions of host cells and infectious virions are mixed and spread on an agar plate,________ form where viruses lyse the host cells.

A)insertion sequences
B)plaques
C)prophages
D)colonies

Question 34

The use of ________ is the easiest and most effective way of studying many animal and plant viruses.

A)bacterial cultures
B)tissue or cell culture
C)live hosts
D)prophages

Question 35

When packaged in the virion,the complete complex of nucleic acid and protein is known as the virus

A)capsid.
B)concatemer.
C)nucleocapsid.
D)envelope.

Question 36

The term "phage" is generally reserved for the viruses that infect

A)animals.
B)plants.
C)bacteria.
D)multiple species.

Question 37

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.

Question 38

The T4 phage protects its DNA from host restriction endonucleases by

A)glucosylating cytosine bases in the T4 genome to prevent DNA cleavage.
B)methylating all four bases (A,T,C,
C)integrating the viral genome into the host genome where it will not be degraded.
D)circularizing the viral genome so that it will not be degraded.
G)in the T4 genome to prevent DNA cleavage.

Question 39

What genome composition makes viruses most susceptible to destruction by prokaryotic restriction endonucleases?

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

Question 40

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)deletion or inactivation of the cI gene
B)deletion or inactivation of the cro gene
C)overexpression of the cro gene
D)deletion of both the cro and cI genes

Question 41

How do bacteriophage influence bacterial evolution?

A)Bacteriophage cause cleavage and rearrangement of bacterial genomes,thus accelerating bacterial evolution.
B)Bacteriophage lyse mutated bacterial cells,thus preventing them from replicating and passing on their genetic information.
C)Bacteriophage transfer genetic information between bacterial cells through transduction,thus increasing the genetic diversity of bacterial populations.
D)Bacteriophage decrease the size of bacterial populations and thus decreasing genetic diversity and slowing down bacterial evolution.

Question 42

In viruses,genetic information flows from ________ to ________.

A)RNA / virion
B)nucleic acid / protein
C)capsid / virion
D)DNA / protein

Question 43

You isolate a purify a bacteriophage that can replicate in E.coli.Through chemical analyses you determine that the only nucleic acid present is RNA.You isolate the RNA and put it in a test tube with all of the necessary proteins and RNAs for translation.The RNA is translated and new infectious virions are made.What does this tell you about the bacteriophage?

A)The RNA genome is of the plus sense.
B)The RNA genome is of the plus sense and RNA replicase is present in the viral capsid.
C)The new bacteriophage is a retrovirus.
D)RNA replicase is present in the viral capsid.

Question 44

What would be the consequence of deleting the late T4 genes?

A)The T4 genome would not be copied.
B)T4 mRNA would not be produced.
C)T4 capsid proteins would not be made.
D)ATP would not be produced and the T4 genome would not be packaged into the capsid.

Question 45

There is at least one known virus whose genome is actually larger than a cellular genome.

Question 46

Some viruses possess icosahedral heads and helical tails.

Question 47

Viruses can redirect host metabolic functions.

Question 48

In the first few minutes after host cell infection,the virus undergoes an eclipse.

Question 49

In a natural population of diverse slow-growing prokaryotic cells,what type of viruses would you expect to be most common?

A)lytic bacteriophages
B)enveloped viruses
C)icosahedral viruses
D)temperate bacteriophages

Question 50

Viruses have both an intracellular and an extracellular form.

Question 51

Most of the genetic diversity on earth resides in viral genomes.

Question 52

The growth of viruses in a culture is described as a one-step growth curve,because

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

Question 53

A cell that allows the complete replication cycle of a virus to take place is said to be a

A)permissive host.
B)viral cell.
C)dead cell.
D)lytic cell.

Question 54

What are the consequences of a viral infection of an animal cell?

A)rapid lysis or latent infections
B)lysogeny followed by eventual lysis
C)lysis or lysogeny
D)Outcomes vary from rapid lysis to persistent infections,latent infections,or cancer.

Question 55

Penetration requires that the entire virus is inserted within the host.

Question 56

The concentration of infectious plaque forming units (pfu)per volume of fluid is known as the

A)infectivity.
B)virulence.
C)titer.
D)fluid infectivity.

Question 57

Viruses can confer additional properties on their host cells,which can in turn be inherited.

Question 58

RNA viruses encode host restriction systems designed to destroy host DNA.

Question 59

For bacteriophages and animal viruses ________ is the step in the viral life cycle that determines host cell or tissue specificity.

A)attachment
B)penetration
C)synthesis
D)assembly

Question 60

Whether lambda phage undergoes the lytic or lysogenic cycle is dependent on the accumulation of

A)Cro protein.
B)viral genomes.
C)cI protein.
D)methylated DNA.

Question 61

The latent phase in the viral growth curve and the lag phase of the bacterial growth curve are equivalent and represent the time it takes for the virus or bacterium to adapt to the culture conditions and begin growing.

Question 62

Explain the relationship between the terms virus particle,virion,and virus genome.

Question 63

The virus repressor protein provides immunity to infection by the same type of virus.

Question 64

Compare and contrast the structure,life cycle,and host cell type of naked and enveloped viruses.

Question 65

What are the potential advantages of lysogeny compared to lysis for a temperate virus?

Question 66

Relate the structure of bacteriophages and animal viruses to the structure of their respective host cells and the steps of the viral life cycle.

Question 67

Lysogeny is unique to bacteriophages; similar relationships have not been found among the animal viruses.

Question 68

Tailed bacterial viruses can be used as genetic engineering tools.

Question 69

A temperate virus does not exist as a virus particle inside the host cell.

Question 70

Although T4 encodes over 250 proteins,it does not encode its own RNA polymerase.

Question 71

How does plating efficiency affect the number of plaque-forming units? How is plating efficiency calculated?

Question 72

An RNA genome itself serves as mRNA in negative-stranded RNA viruses.

Question 73

Describe the establishment and maintenance of the lysogenic state in the lambda phage.

Question 74

Temperate viruses can enter into either a lytic or lysogenic cycle.

Question 75

RNA replicase is found in ALL viruses to allow the replication and transcription of viral RNA instead of host RNA.

Question 76

A lytic infection results in death of the host cell.

Question 77

Compare and contrast a typical bacterial growth curve and a viral one-step growth curve.Explain why the growth curves are different based on bacterial and viral replication.

Question 78

Influenza is an acute human viral disease that causes brief cellular damage followed by healing and complete clearing of the virus from the body. Hepatitis C is a chronic viral disease that causes slow destruction of tissue and persistent virions that are not completely cleared.Which of these diseases is more likely to be caused by lytic virus and which is caused by a lysogenic virus?

Question 79

T4 and other bacteriophages commonly use a method of DNA replication and packaging called "headful packaging." Explain how viral genomes are replicated and packaged in this process and hypothesize how headful packaging might affect evolution of BOTH the bacteriophages and their prokaryotic hosts.

Question 80

Why was the discovery of retroviruses important to the field of molecular biology?