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WorksheetsViro (testbank #2)
Total questions: 160
Worksheet time: 3hrs 34mins
Which of the following terms describes the protein shell that surrounds the viral genome?
(a)
Which of the following would not be a nucleic acid form found in a viral genome?
dsDNA
ssDNA
dsRNA
ssRNA
an RNA:DNA hybrid
Which of the following is an enzyme that most RNA viruses encode in their genome?
DNA-dependent-RNA-polymerase
RNA-dependent-RNA-polymerase
DNA-dependent-DNA-polymerase
DNA-dependent-RNA-polymerase
RNA-dependent-protein-synthetase
Viruses play a major role in the ecology of the ocean by doing which of the following?
By infecting photosynthetic bacteria and increasing their growth.
By infecting harmful bacteria found in the ocean and limiting their growth.
By killing off fish and preventing them from becoming too plentiful.
By lysing unicellular organisms and releasing carbon and oxygen back into the ocean.
All of the above statements are correct.
If you wanted to show that an infectious agent is a virus, what experiment could you do?
Show that the agent can be seen under a light microscope.
Show that agent contains a lipid membrane.
Show that the agent can form single colonies on an agar plate.
Show that the agent can be diluted and can still cause disease in an animal.
Show that the agent can pass through a porcelain filter and is still infectious.
What does the word “virus” mean in Latin?
(a)
The word “phage” is a shortened version of the name of a virus that can infect which type of organism?
(a)
The study of which group of viruses led to the discovery of cellular genes that can promoter cancer in animal cells?
(a)
When doing a plaque assay with human or animal cells, a layer of nutrient media mixed with agar is put on top of the cells after they have been infected with the diluted virus. What is the major purpose of this agar layer?
It helps to feed the cells as they grow.
It promotes the replication of the virus.
It makes the infected cells easier to visualize.
It limits the movement of virus particles.
All of the above are correct.
To start an experiment, you do an infection by putting 0.5ml of a virus stock that has a titer of 6x107pfu/ml onto a plate of animal cells that contains 5x106cells . What is the multiplicity of infection for this experiment?
12
6
5
3
1
During a single growth cycle experiment, the titer of extracellular and intracellular virus drops in the first hour. What explains this observation?
The virus is inactivated by antibodies in the medium.
The virus is inactivated by cellular enzymes.
The virus enters the cell and is uncoated.
The virus binds to the cells in the dish and can’t be released.
The cell’s antiviral defenses prevent replication of the virus
What is another term for an RNA-dependent-DNA-polymerase?
(a)
Plant viruses use which cellular structures to spread between host cells?
(a)
All viruses that use a negative-sense RNA genome must package which of the following proteins in their virion?
RNA-dependent-RNA-polymerase
matrix protein
RNA helicase
RNA methylase
scaffolding protein
Which of the following is a description of a plaque?
A viral particle as seen by electron microscopy.
A region of dead cells in a monolayer of infected cells.
A skin lesion caused by a virus infection in an animal.
A button of red blood cells seen in a hemagglutination assay.
A region of crystallized virus particles in an infected cell.
Which of the following processes in cells was NOT discovered by studying a virus?
the sequence of the genetic code.
DNA replication in both prokaryotic and eukaryotic cells
DNA is the genetic material
regulation of gene expression in eukaryotic cells.
mRNA splicing in eukaryotic cells
You are given a solution of virus and asked to determine the titer. You carry out a plaque assay with 0.5 mls of a 105 dilution of the virus solution and obtain an average of 150 plaques. What is the titer of the solution?
1.5×105 pfu/ml
3×105 pfu/ml
1.5×107 pfu/ml
3×107 pfu/ml
1.5×108 pfu/ml
The Baltimore classification system describes the relationship between a viral genome and the:
the complementary genome sequence.
early viral proteins.
early mRNAs.
cellular polymerases.
Latin classification system.
If the genome of a positive-strand RNA virus, which has been purified away from all of the virion proteins, was injected into the cytoplasm of an appropriate host cell, what would happen first?
The genome would be copied into complementary negative RNA.
The genome would be translated by cellular ribosomes.
The genome would be transcribed by a cellular RNA-dependent-RNA-polymerase.
The genome would be transcribed by a viral RNA-dependent-RNA-polymerase.
None of the above.
If the genome of a negative-strand RNA virus, which has been purified away from all of the virion proteins, was injected into the cytoplasm of an appropriate host cell, what would happen first?
The genome would be copied into complementary negative RNA.
The genome would be translated by cellular ribosomes.
The genome would be transcribed by a cellular RNA-dependent-RNA-polymerase.
The genome would be transcribed by a viral RNA-dependent-RNA-polymerase.
None of the above.
Most DNA viruses that replicate in the nucleus of the host cell use which of the following to transcribe their genes into mRNA?
cellular DNA-dependent-RNA polymerase
viral DNA-dependent-RNA polymerase
viral DNA-dependent-DNA polymerase
cellular DNA-dependent-DNA polymerase
viral RNA-dependent-DNA polymerase
The development of which of the following instruments or techniques in the 1930’s allowed scientists to visualize viral particles for the first time?
polymerase chain reaction
electron microscope
confocal microscope
thermal cycler
plaque assay
The lipid membrane that surrounds the nucleocapsid of some virus particles is called the:
(a)
Question type: Multiple Choice. The nucleocapsid describes the structure that includes the:
capsid and the genome
capsid and the envelope
envelope and the glycoproteins
helical capsid and an envelope
icosahedral capsid and an envelope
Question type: Multiple Choice. Depending on the type of virus, which of the following is a function of the virus capsid?
To attach to the correct type of host cell.
To protect the viral genome from nucleases.
To ensure delivery of the genome into the host cell.
To protect the viral genome from damage by UV light.
All of the above functions are correct.
Question type: Multiple Choice. Virus particles can be visualized with which of the following?
negative staining of virions with electron microscopy
negative staining of virions with x-ray diffraction
negative staining of thin sections of infected cells with electron microscopy
positive staining in cryoelectron microscopy
Most viruses that use a spherical shaped capsid arrange their capsid proteins with which of the following symmetries?
cubic
tetrahedral
icosahedral
dodecagon
helical
Which of the following is NOT a characteristic of a regular icosahedron?
It has 12 vertices of 5-fold symmetry.
It has 20 triangular faces.
It has 20 sides with 3-fold symmetry.
It has 30 edges with 2-fold symmetry.
It has 6 square faces.
How many copies of the capsid protein would there be in an icosahedral capsid with a Triangulation number of 7?
70
210
280
420
490
Which of the following h and k values will produce a triangulation number of 13?
1 and 1
1 and 2
1 and 3
2 and 3
2 and 4
The capsid of SV40 contains 360 protein copies. Why is this unusual?
There is only 1 kind of protein in this capsid.
360 is not the correct number of protein capsids for a T = 6 capsid.
Six is not a mathematically allowed triangulation number.
The proteins have equivalent interactions.
The capsid is not large enough to hold the entire genome.
The Jelly Roll barrel is:
a structure found in many viral envelope glycoproteins.
a structure found in many viral capsid proteins.
the structure the viral genome takes inside of a helical capsid.
the structure the viral genome takes inside an icosahedral capsid.
the structure of many helical capsids as the wrap around the genome.
Which of the following describes the number of subunits per turn in a helical capsid?
P (pitch)
μ (mu)
ρ (rho)
Triangulation number
symmetry
A very common structure for bacteriophage particles is which of the following?
an icosahedral head and an envelope
a naked icosahedral head
a naked helical tail
an icosahedral head with a helical tail
a cubic head with a helical tail
A Type I membrane protein has which of the following structures?
Both the C-terminus and the N-terminus face the inside of the virion.
It passes through the viral envelope multiple times.
The N-terminus faces outside the virion and the C-terminus faces inside the virion.
The N-terminus faces inside the virion and the C-terminus faces outside the virion.
The protein lacks a transmembrane domain and is secreted from the infected cell.
What does the term “quasi-equivalent” mean with respect to the proteins in an icosahedral capsid?
If the identical protein is used, it has both 5-fold and 6-fold interactions with the other proteins in the capsid.
There are different proteins in the capsid with similar shapes.
They all use the “jelly-roll” protein structure.
There can be more than one type of glycoprotein in the envelope.
All of the proteins interact in a 5-fold arrangement.
Which of the following is a description of a scaffolding protein?
A cellular protein that acts as a chaperone during assembly of a helical capsid.
A viral protein that is used on the outside of an icosahedral capsid during assembly.
A viral protein used on the inside of an icosahedral capsid during assembly and then removed.
A protease that trims the proteins during assembly of an icosahedral capsid.
A energy dependent motor used to package the genome into larger icosahedral capsids.
A scaffolding protein is important for assembly of an icosahedral capsid.....
but does not bind to the viral genome.
but does not become part of the final virion.
and helps to cut the genome into unit lengths.
and binds to the host cell receptor.
and assists the virion in exiting the host cell.
A packaging sequence is involved in which of the following assembly processes?
The assembly of the capsid around the genomic nucleic acid.
The correct binding of capsid proteins to each other.
The insertion of the viral glycoproteins in the envelope.
The acquisition of the envelope by the capsid.
The packaging of the matrix proteins into the virion.
In a helical nucleocapsid, which of the following MOST affects the LENGTH of the capsid?
the μ (mu) value
the ρ (rho) value
the size of the genome and the P (pitch) of the helix
the size of the capsid protein
None of the above.
Enveloped virions assemble and acquire their envelope by which of the following mechanisms?
The nucleocapsids interact directly with the cytoplasmic tails of the envelope glycoproteins and bud through the cellular membrane.
The nucleocapsids interact with the matrix protein, which interact with the cytoplasmic tails of the envelope glycoprotein, and the virion buds through the cellular membrane.
The envelope is assembled de novo around the nucleocapsid by cellular enzymes.
The virion acquires the envelope after it leaves the host cell from extracellular vesicles.
Both a and b are used by viruses.
Viral proteins that assemble between the nucleocapsid and the envelope are called
(a)
Which of the following types of genomes is most commonly found in viruses that can infect fungi?
ssDNA
dsDNA
ssRNA
dsRNA
All of the above are found.
The name of a virus family in the Latin classification system has which of the following endings?
-viridae
-virales
-virinae
-virus
-virusdae
The family classification scheme for DNA bacteriophages is not very useful for describing the evolutionary relationships between these viruses. What is the best explanation for this?
DNA bacteriophages can infect more than one host species.
DNA bacteriophages have a wide variety of virion structures.
The viral genomes are genetic mosaics due to recombination.
There are too many bacteriophages to classify into families.
These viruses do not have an evolutionary relationship to each other.
Which of the following is a type of nucleic acid NOT found as the genome of a virus that can infect vertebrates?
ssDNA
dsDNA
ssRNA
dsRNA
All of the above are found.
Most viruses that infect plants have the following type of genome?
ssDNA, positive sense
ssDNA, negative sense
ssRNA, positive sense
ssRNA, negative sense
None of the above.
What is a possible explanation for why ssDNA viruses have genomes less that 10kb in size?
ssDNA is not as physically stable as dsDNA.
ssDNA is not transcribed by host cells.
ssDNA can form hairpin structures because of base-pairing.
Larger pieces of ssDNA can not be replicated.
Larger pieces of ssDNA can not easily enter the host cell.
An interesting observation is that many highly pathogenic and deadly human viruses have the following type of genome?
ssDNA, positive sense
ssDNA, negative sense
ssRNA, positive sense
ssRNA, negative sense
dsRNA
Which of the following virus families have the ability to synthesize reverse transcriptase?
Retroviruses
Caulimoviruses
Hepadnaviruses
None of the above are correct.
All of the above are correct.
What distinguishes a satellite virus from a satellite nucleic acid?
A satellite virus encodes its own capsid protein while a satellite nucleic acid does not.
A satellite virus packages its own replication protein while a satellite nucleic acid does not.
A satellite virus requires a helper virus while a satellite nucleic acid does not.
Genomes of satellite viruses are smaller than those of satellite nucleic acids.
Satellite viruses do not encode any proteins while satellite nucleic acids do.
What is a ribozyme?
A molecule of RNA that is independently capable of replicating without cellular enzymes.
A molecule of RNA that codes for an enzyme.
Another name for a small infectious molecule of RNA.
A virus that uses a small piece of RNA as its genome.
A molecule of RNA that can carry out an enzymatic process.
According to the RNA World hypothesis, which of the following subcellular entities may have evolved first?
Retroviruses
RNA Viruses
Viroids
DNA Viruses
Bacteriophages
According to the RNA World hypothesis, which of the following enzymes may have evolved first?
DNA-dependent RNA polymerase
DNA-dependent DNA polymerase
RNA-dependent RNA polymerase
RNA-dependent DNA polymerase
self-replicating RNAs
Which of the following virus families contains viruses with the longest ssRNA genomes?
Picornaviruses
Coronaviruses
Flaviviruses
Togaviruses
Bromoviruses
What is approximately the largest size of a double-stranded DNA genome of a virus that infect vertebrates?
25 kbp
50 kbp
100 kbp
300 kbp
500 kbp
Almost all of the viruses with positive-strand RNA genomes and enveloped virions infect which group of hosts?
Bacteria
Vertebrates
Plants
Fungi
Algae
Which of the following may be a factor in explaining why viral ssRNA genomes are not usually as long as the dsDNA genomes?
It is much more difficult to package a large ssRNA genome into a capsid.
Long ssRNA molecules form too many secondary structures that inhibit replication.
Long RNA genomes are difficult to translate.
Long RNA genomes are difficult to transcribe.
Long pieces of RNA are easily broken by mechanical damage.
The advantage of using a helical instead of an icosahedral nucleocapsid to package a ssRNA genome is.....
it is more efficient to envelope a helical nucleocapsid than an icosahedral capsid.
A fusion of two cells causes by viral envelope glycoproteins.
it better protects the genome from degradation inside the cell.
it requires a smaller protein to build than an icosahedral capsid.
it requires fewer copies of the nucleocapsid protein than an icosahedral capsid.
There are a number of small DNA viruses that are highly dependent on their host cells for transcription and replication enzymes. Which of the following could explain the evolutionary origins of these viruses?
They originated from fragments of the genomes of larger more independent viruses.
They originated from intracellular plasmids found in bacteria.
They originated from the genomes of intracellular organelles, such as mitochondria.
They originated from fragments of cellular DNA that broke away from the cell genome.
All of the above could be correct.
Because of the rigid plant cell wall, the entry of plant viruses is difficult. Which of the following is a description of how plant viruses move between individual cells within a whole plant?
They move between cells using plasmodesmata.
They cause the formation of syncytia.
They use the receptor mediated endocytosis pathway.
They rely on insect vectors to transfer virions between the cells in a single host.
They produce movement proteins that can create holes in the plant cell wall, allowing movement of the virions between cells.
Which of the following is the best description of a syncytia?
A cellular structure that viruses us to move within a host cell.
A fusion of two cells causes by viral envelope glycoproteins.
A structure between two plant cells that viruses can use for cell to cell movement.
A vesicle involved in the receptor mediated endocytosis pathway.
A protein that is involved in the transport of proteins into the nucleus.
Orthymyxoviruses and paramyxoviruses both bind to which receptor on the surface of which host cells?
an immunoglobulin family receptor protein
the CD4 protein
the carbohydrate sialic acid
the neuraminidase enzyme
a multiple membrane spanning transport protein
Which of the following is an example of a virus that requires two different host cell receptors to complete its entry into the host cell?
HIV-1
Adenovirus
Polio (picornavirus)
Influenza virus (orthomyxovirus)
Both HIV an Adenovirus require two cell receptors for entry.
Which of the following organelles is used as a sorting and recycling station in the receptor mediated endocytosis pathway?
Early endosome.
Clatherin-coated vesicle.
Lysosome.
Golgi apparatus.
Caveolae.
Most viruses must exit the endosome before it fuses with a lysosome. Why?
Their envelope will not fuse easily with the lysosomal membrane.
To avoid the very low pH in the lysosome, which causes destructive conformational changes.
To avoid being degraded by lysosomal proteases and nucleases.
To enhance their movement towards the nucleus of the cell.
The pH of the lysosome is too high to induce membrane fusion.
Which of the following is an accurate description of caveolae?
Small, flask-shaped invaginations of the plasma membrane enriched in cholesterol.
Vesicles surrounded by a cage of clatherin proteins.
Regions of the plasma membrane rich in cell signaling molecules.
A cytoskeletal network that is involved in transport of vesicles to the nucleus.
A cellular motor protein that is involved in intracellular transport.
The major difference between class I fusion proteins and class II fusion proteins is that ....
class I proteins mediate fusion at the plasma membrane and class II proteins mediate fusion with the endosome membranes.
only class I proteins contain fusion peptides.
only class II proteins have a transmembrane domain.
only class I proteins undergo large conformational changes within the protein during entry.
class I proteins are found in unenveloped virus particles while class II proteins are found in enveloped particles.
Adenoviruses use which of the following entry mechanisms?
The fibers on the virion can penetrate the endosome membrane can cause it to lyse open.
An interaction between the penton base of the virus and the cellular integrin proteins causes the endosome membrane to lyse open.
The capsid forms a pore through the cell membrane and extrudes the genome into the cytoplasm.
The viral envelope fuses at the plasma membrane after binding to the host integrin protein.
The viral envelope fuses with the nuclear membrane after binding to the nuclear pore complex.
Inhibition of the M2 protein of influenza with the drug amantadine will block which step of virus entry?
fusion of the viral envelope with the endosome membrane.
movement of the RNA genome segments through the nuclear pore.
the conformational change that the HA proteins exhibit in response to the drop in pH.
binding to sialic acid on the surface of the host cell.
unpacking of the viral RNA genome segments from the virion.
Why would some viruses have the enzyme neuraminidase, which can cleave their receptor sialic acid from membranes, in their envelopes?
It removes sialic acid from the viral envelope so that it doesn’t interfere with binding to the next host cell.
It allows virions to mature their envelope proteins so that they can attach to the next host cell.
It prevents the virions from attaching to dead cells, which would not lead to a productive infection.
It removes sialic acid from the host cell membranes, which exposes their high affinity protein receptor.
It allows the released virus particles to move more easily through the extracellular matrix.
Many large DNA viruses use which of the following cellular components to get their nucleocapsid near to the host cell nucleus
intermediate filaments
nuclear pore complex
actin filaments
microtubules
importins
What mechanism do most retroviruses, but not HIV, use to get their genome into the host cell nucleus?
They actively inject their genome into the nucleus through the nuclear pore complex.
These viruses do not need to enter the nucleus to replicate.
They attach their genome to importin proteins which carry them into the nucleus.
They wait until the cell enters mitosis and the nuclear envelope breaks down.
The genome is bound to viral proteins that contain nuclear localization signals that move the genome through the nuclear pore complex.
Which of the following describes the function of dynein?
It is a protein involved in importing cargo into the nucleus through the nuclear pore complex.
It is a motor protein that moves along microtubules towards the nucleus.
It is a motor protein that moves along microtubules towards the cell periphery.
It is a cell structure used to pass virus particles directly between host cells.
It a cellular membrane protein used as a cell receptor by many viruses.
Which of the following statements is a good explanation for the observation that many different rhinovirus strains can all use the same host cell receptor?
The receptor binding site is buried at the base of a narrow canyon on the viral capsid which is inaccessible to antibody proteins.
The receptor binding site is the most exposed area of the capsid which is highly accessible to antibody proteins.
The amino acid sequence of the canyon region of the capsid is highly variable.
A soluble form of the CD4 protein was once investigated as a treatment for HIV infection. How would this protein work to block infection.
It would raise the pH of the endosome and prevent activation of the fusion protein.
It would bind to the cell membrane and prevent fusion of the HIV virion with the plasma membrane.
It would interact with the host cell receptor and prevent binding by the virion glycoprotein.
It would interact with the HIV envelope glycoprotein and block its interaction with the host cell receptor.
It would inhibit entry of the viral genome into the cell nucleus.
As part of an experiment, you take a solution of purified influenza virus particles and lower the pH of the solution to 5.5. You then add the virus to a culture of the appropriate host cell. What do you think would happen?
The HA protein would become inactivated and the virus would not be able to enter the host cell.
The viral genome would be degraded and the virus would not be able to start the infection.
The HA protein would be able to bind more tightly to the host cell receptors.
The cell would not be able to take up the virus particles into clathrin coated pits.
The virus particles would not be able to be transported into the nucleus.
The interaction between the viral particle and the host cell receptor is a major determinant of the species specificity of viral infections.
True
False
Most DNA viruses replicate in the cytoplasm of the host cell, since the ribosomes they need to translate their mRNAs are located in this cellular compartment.
True
False
Which of the following structures found on E. coli cells is required for infection with a ssRNA phage?
Cell wall
Lipopolysaccharide
F-pili
Cell surface receptor
All of the above are required.
The discovery of the ssRNA phages was useful to scientists working on which of the following processes:
Structure of ribosomal RNA
Translation of messenger RNA
Structure of proteins
Transcription of messenger RNA
Replication of DNA
Why are ssRNA phages used as an index organism to detect the presence of pathogenic enteroviruses in the sewage treatment process?
The RNA phage are smaller than the pathogenic viruses.
The RNA phage are easier to inactivate than the pathogenic viruses.
The RNA phage are more stable than the pathogenic viruses.
The RNA phage are easier to quantify using a plaque assay than the pathogenic viruses.
The RNA phage are easier to see with an electron microscope than the pathogenic viruses
Translational readthrough occasionally occurs in the coat protein gene of the ssRNA phage QI. Which of the following describes this process?
The stop codon (UGA) is read as a tryptophan codon (UGG).
The RNA-dependent RNA polymerase reads into the next gene.
The RNA-dependent RNA polymerase inserts an extra base in this gene.
The ribosome shifts back one base and reads a different reading frame.
The ribosome shifts forward one base and reads a different reading frame.
How is the structure of an RNA phage virion different from the structure of the virion of many dsDNA phages?
They have much shorter tails than the DNA phages.
The heads do not use icosahedral symmetry.
The icosahedral head has a very large triangulation number.
They are solely composed of a helical nucleocapsid.
They lack the tail structure used to inject the genome into the host cell.
Which of the following proteins in the virions of the ssRNA phages binds to the F-pilus during virus attachment and entry?
Lysis protein
Attachment protein
Coat protein
Maturation protein
Replicase protein
When an RNA phage virion is assembled with either a defective or missing maturation protein, which of the following occurs?
The viral RNA genome is more sensitive to RNAse degradation.
The virion is more sensitive to protease degradation.
The virion is unstable and disassembles easily in the environment.
The virion is not able to carry out genome replication.
The tail cannot inject the genome into the host cell.
Once the RNA genome of QI is released into the host cell, which of the following describes the first step in the viral replication cycle?
Translation of the genomic RNA by host ribosomes to produce the replicase protein.
Reverse transcription of the RNA genome into DNA by a viral reverse transcriptase.
Transport of the RNA genome into the nucleus for integration into the host genome.
Packaging of the genomic RNA into progeny virions before protein synthesis begins.
The bacteriophage MS2, which has a ssRNA genome, must produce many more copies of the coat protein than of the replicase and lysis proteins. Which of the following genome features controls how much of each protein is produced?
Translational control sequences at the 3’ end of the genome
Translational control sequences at the 5’ end of the genome
Secondary structure of the RNA genome
The strength of the transcriptional promoters
The location of the transcriptional terminators
Which of the following genes from the ssRNA phage MS2 is translated immediately upon entry of the viral genome into the host cell?
Maturation protein gene
Lysis protein gene
Coat protein gene
Replicase gene
A1 gene
In the ssRNA phage MS2, the replicase and lysis proteins are NOT produced immediately upon entry of the viral genome. Which of the following mechanisms is the primary explanation for why this happens?
The start codons for these genes are buried in a very stable stem-loop structure.
They have Shine-Dalgarno sequences that do not bind well to the ribosome.
They both contain non-canonical TTG start codons.
The genes encoding these proteins are uncoated from the capsid until later.
The initiator tRNA does not bind well to the start codons of these genes.
In the ssRNA phage MS2, translation of the lysis protein gene is dependent on which of the following events?
Replication of the viral genomic RNA.
Initiation of translation of the replicase gene.
Binding of the coat protein to the nucleation site on the genome.
Termination of translation of the coat protein gene.
Initiation of translation of the maturation gene.
Site directed mutagenesis of the MS2 genome was carried out to abolish the MJ stem structure that is just upstream of the start codon of the replicase gene. Which of the following describes the result of this experiment?
The coat protein was unable to bind to the viral genome.
The maturation protein was unable to bind to the stem-loop.
The ribosome could no longer bind to the start codon for the replicase gene.
The replicase protein was unable to bind to the viral genome.
Translation of replicase gene increased in the absence of coat protein translation.
What is the function of Host Factor during the replication of the Qβ RNA genome?
It delays the folding of the RNA into its final secondary structure.
It makes the 3’ end of the genome more accessible to the replicase enzyme.
It adds a non-template A nucleotide to the 5’ end of the minus strand.
It facilitates binding of the replicase protein to the coat protein start codon.
It prevents binding of the replicase enzyme to the 5’ end of the genome.
In the ssRNA phage MS2, binding of the coat protein to which of the following RNA structures acts to initiate packaging of the viral RNA into the capsids.
The 5’ end of the genome
The 3’ end of the genome
The MJ stem loop
The start codon of the coat protein gene
The operator stem loop
In the ssRNA phage MS2, the replicase protein binds to the start codon of the coat protein gene. Which of the following describes the reason for this binding?
It prevents replication and translation from occurring simultaneously.
It initiates synthesis of the minus-strand copy of the genome.
It enhances binding of the ribosome to the coat protein gene.
It disrupts the stem-loop structure that prevents replication of the viral genome.
It exposes the 3’ end of the genome which allows the replicase to begin RNA synthesis.
The viral polymerase complex from the RNA phage Qβ contains which of the following host cell proteins?
Host Factor
S1 ribosomal protein
EF-Tu translational factor
EF-Ts translational factor
All of the above are part of the complex.
In the ssRNA phage Qβ the synthesis of the plus strand RNA genome from the negative strand template does not require the ribosomal S1 protein. Which of the following explains why?
The minus strand is shorter and takes less time to replicate
The minus strand lacks the secondary structure that prevents replication.
There is no competition between binding of the replicase enzyme and the ribosome.
The replicase enzyme is more processive when copying the minus strand.
The minus strand has a lower GC content than the plus strand.
In the ssRNA phage MS2, the maturation protein is only produced after which of the following events occurs?
The synthesis of the negative strand of the viral genome.
The synthesis of the positive strand of the viral genome.
Packaging of the viral genome into new capsids.
Translation of the coat protein.
Folding of the newly synthesized genome into the stable secondary structure.
The replicase enzyme of the ssRNA phage Qβ has been used by scientists to do which of the following?
Synthesize RNA molecules from a DNA template.
Measure small amounts of target RNA molecules in a sample.
Measure the levels of pathogenic viruses in drinking water.
Amplify DNA molecules in a sample.
Fuse two pieces of RNA together.
Replication and translation can occur simultaneously on a single molecule of genomic RNA from the ssRNA phage MS2.
True
False
During the replication cycle of the ssRNA phage MS2, the lysis gene can not be translated in the absence of translation of the coat protein gene.
True
False
Which of the following was used to distinguish different bacteriophages before the development of the electron microscope in the 1930’s?
Western blot
DNA sequence
DNA restriction analysis
X-ray crystallography
Plaque morphology
What distinguishes the small bacteriophage φX174 from many other bacteriophages?
The virion has a very large head.
The virion has a very long tail.
It has a single-strand DNA genome.
It has a single-strand RNA genome.
It has a double-strand RNA genome.
Which of the following bacteriophages had its entire genome sequenced first?
MS2
φX174
Lambda phage
T4
T3
Several different mRNAs are produced from the φX174 genome using which of the following mechanisms?
Multiple transcription promoters
Multiple transcription terminators
Multiple translation start sites
Multiple stop codons
Both a and b are correct
The phage φX174 can tolerate mutations in the non-structural region of its genome more easily than in the structural region of the genome. Which of the following explains why?
Not all of the proteins coded in this region are packaged into the mature capsid.
Single-stranded DNA is not as easily mutated as double-stranded DNA.
Many of the non-structural proteins have more than one function.
Some of the non-structural proteins are non-essential for virus replication.
The presence of overlapping reading frames in this region of the genome.
Which of the following is used as the primary host cell receptor for the phage φX174?
Glucose on lipopolysaccharide
A membrane protein
The cell wall
The F-pili
The internal membrane
Entry of the viral genome for φX174 appears to occur at which locations on the host cell?
The surface of the F-pili
Cell wall adhesion regions
The base of the flagella
Regions of high lipopolysaccharide
All of the above
Why must the microviruses produce dsDNA before viral genes can be expressed?
Only dsDNA can be packaged into virions.
DsDNA is more stable than ssDNA.
Only dsDNA is a substrate for transcription by the host RNA polymerase.
Only dsDNA is a substrate for replication by the host DNA polymerase.
The viral regulatory proteins can only bind to double-stranded DNA.
Which of the following bacteriophages has a genome composed of ssDNA?
lambda phage
ΦX174
T7
MS2
Qβ
Which of the following processes was studied by working with the phage ΦX174?
Transcription of mRNA
Splicing of mRNA
Translation of mRNA
Replication of DNA
Lysogeny
Before the viral genome can be transcribed or replicated in a new host cell it must….
be trimmed by cellular nucleases.
enter the host cell nucleus and be bound by cellular histone proteins.
be transported through the receptor mediated endocytosis pathway.
be processed through the cellular exocytosis pathway.
be uncoated in the appropriate compartment of the correct cell type.
Unenveloped viruses must get their genome past the hydrophobic cell membrane. Some accomplish this by doing which of the following?
They cause the plasma membrane to lyse.
They insert viral proteins into a vesicle membrane.
They inject their genome into the nucleus via the nuclear pore complex
They create a pore through the membrane and extrude the genome directly into the cytoplasm
They create a clatherin coated pit during entry
Inhibition of the M2 protein of influenza with the drug amantadine will block which step of virus entry?
fusion of the viral envelope with the endosome membrane.
movement of the RNA genome segments through the nuclear pore
the conformational change that the HA proteins exhibit in response to the drop in pH
binding to sialic acid on the surface of the host cell
unpacking of the viral RNA genome segments from the virion
Bacteriophage T7 was isolated from what source?
Unprocessed waste from a sewage treatment plant
Commercially available treatment for intestinal infections
c) Soil found on a farm
d) Water samples taken from a polluted river
e) Animal manure
Used for the primary isolation of certain viruses and for studies for the pathogenesis of viral diseases and of viral oncogenesis
in vivo
in vitro
research-based
Central to the cultivation and characterization of viruses.
in vivo
in vitro
research-based
basic type of cell culture by dispersing from freshly removed host tissues. Generally, unable to grow for more than a few passages in culture.
(a)
Some viruses are characterized by helical symmetry of the viral nucleocapsid. Which of the following statements about viruses with helical symmetry is most accurate?
(A) All enveloped viruses with helical symmetry are classifed into the same virus family.
(B) Helical nucleocapsids are found primarily in DNA-containing viruses.
(C) All human viruses with helical nucleocapsids possess an envelope.
(D) Excess empty helical particles containing no nucleic acid are commonly produced in infected cells.
Virus-infected cells often develop morphologic changes referred to as cytopathic effects. Which of the following statements about virus-induced cytopathic changes is most accurate?
A) are pathognomonic for an infecting virus.
(B) are rarely associated with cell death.
(C) may include giant cell formation.
(D) can only be seen with an electron microscope.
Viruses usually initiate infection by first interacting with receptors on the surface of cells. Which of the following statements is most accurate about cellular receptors for viruses?
(A) Cellular receptors for viruses have no known cellular function.
(B) All viruses within a given family use the same cellular receptor.
(C) All cells in a susceptible host express the viral receptor.
(D) Successful infection of a cell by a virus may involve interaction with more than one type of receptor.
Which of the following can be used to quantitate the titer of infectious viruses?
(A) Plaque assay
(B) Electron microscopy
(C) Hemagglutination
(D) Polymerase chain reaction
(E) Enzyme immunoassay
Which one of the following states a principle regarding viral nucleic acid?
(A) Viruses contain both RNA and DNA.
(B) Some viruses contain a segmented genome.
(C) Purifed viral nucleic acid from any virus is usually infectious.
(D) Viral genome sizes are similar among known human viruses.
Two mutants of poliovirus have been isolated, one (MutX) with a mutation in gene X and the second (MutY) with a mutation in gene Y. If cells are infected with each mutant alone, no virus is produced. If a cell is coinfected with both MutX and MutY, which one of the following is most likely to occur?
(A) Reassortment of genome segments may occur and give rise to a viable wild-type virus.
(B) genomes may be reverse transcribed to DNA and both MutX and MutY viruses produced.
(C) Complementation between the mutant gene products may occur and both MutX and MutY viruses produced.
(D) cells will transform at high frequency because they will not be killed by the poliovirus mutants.
Which one of the following viruses possesses an RNA genome that is infectious when purified?
(A) Influenza virus
(B) Poliovirus
(C) Papillomavirus
(D) Measles virus
(E) Rotavirus
Viruses belonging to which of the following groups are likely to establish latent infections?
(A) Poxviruses
(B) Filoviruses
(C) Herpesviruses
(D) Influenza viruses
(E) Caliciviruses
Some viruses encode for a viral RNA-dependent RNA polymerase. Which of the following states a principle about viral RNA polymerases?
(A) All RNA viruses carry RNA polymerase molecules inside virus particles because they are needed to initiate the next infectious cycle.
(B) Antibodies against the viral RNA polymerase neutralize virus infectivity.
(C) Negative-strand RNA viruses supply their own RNA dependent RNA polymerase because eukaryotic cells lack such enzymes.
(D) viral RNA polymerase protein also serves as a major core structural protein in the virus particle.
Which of the following statements regarding virus morphology is true?
(A) All RNA viruses are spherical in shape.
(B) Some viruses contain flagella.
(C) Some viruses with DNA genomes contain a primitive nucleus.
(D) Viral surface proteins protect the viral genome from nucleases.
(E) Helical nucleocapsids are found with single-stranded DNA viruses.
Many viruses can be grown in the laboratory. Which of the following statements about virus propagation is not true?
A) Some viruses can be propagated in cell-free media.
(B) Some mammalian viruses can be cultivated in hen’s eggs.
(C) Some viruses with broad host ranges can multiply in many types of cells.
(D) Some human viruses can be grown in mice.
(E) Most virus preparations have particle-to-infectious unit ratios greater than 1.
Laboratory infections can be acquired when working with viruses unless good laboratory safety practices are followed. Which of the following is not a good biosafety practice?
(A) Use of biosafety hoods
(B) Use of laboratory coats and gloves
(C) Avoidance of pipetting by mouth
(D) Flushing experimental waste down laboratory sink
(E) Not eating or drinking in the laboratory
Small viruses are in the same size range as which of the following?
(A) Staphylococcus species
(B) Serum globulin
(C) Red blood cells
(D) Eukaryotic ribosomes
(E) Mitochondria
Which of the following is not an important factor contributing to the phenomenon of emerging viral diseases?
(A) International air travel
(B) Antibiotic resistance
(C) Deforestation
(D) War
(E) Organ and tissue transplantation
Arboviruses are classified into several different virus families but are grouped together based on which of the following common characteristics?
(A) Replicate only in humans
(B) Contain both RNA and DNA
(C) Are transmitted by vectors
(D) Cause hemorrhagic fevers
(E) Cause encephalitis
a period during viral cycle when the virion interacts with the host cell and loses its measurable infectivity. one of the intense synthetic activity as the cell is redirected toward fulfilling the needs of the viral parasite.
(a)
This infection occur in permissive cells and result in the production of infectious virus.
productive infections
abortive infections
latent infection
lysogenic infection
latent infection
type of infection where the host cell fails to produce infectious progeny, either because the cell may be nonpermissive and unable to support the expression of all viral genes, or the infecting virus may be defective, lacking some functional viral gene.
productive infections
abortive infections
latent infection
lysogenic infection
lytic infection
the infecting virion remains inactive inside the host cell but does not integrate into the host genome, therefore, no virion production. its reactivation can result to active infection.
productive infections
abortive infections
latent infection
lysogenic infection
lytic infection
the infecting virion uses the host cell's machinery to replicate and assemble new virions. it results to host cell lysis
productive infections
abortive infections
lytic infection
lysogenic infection
latent infection
the infecting virion's genome becomes part of the host genome. its reactivation results in lytic infection.
productive infections
abortive infections
latent infection
lysogenic infection
lytic infection
the virus that remains inside the host cell by integrating its viral genome into the host cell's unique sites. (host genome u; stable plasmid P1)
(a)
the process that involves the transfer of genes between cells
(a)
a type of transduction that packages the bacterial DNA into the phage head
(a)
it involves the inaccurate excision of prophage; some phage DNA and bacterial DNA are packaged together in the same phage head
(a)
a process that involves the activation of the lysogenic lambda phage, it self-excision from the host genome, entering the lytic cycle, producing new virions, and lyses the host cell.
(a)
a type of gene that maintains the lysogeny of the viral genome
lambda repressor (Cl gene)
Cro protein
RecA
Int
a type of gene that promotes the lytic expression of the viral genome
lambda repressor (Cl gene)
Cro protein
a type of gene that stimulates the cleavage of the Cl repressor and is activated only when the host DNA is damaged
lambda repressor (Cl gene)
Cro protein
RecA
Int
these genes work together to remove the prophage from the host cell genome during the induction process
(a)
The first HIV drug, initially discovered during screening for anti-tumor cell compounds. Mutants arose immediately after this drug was licensed to use.
(a)
This drug interacts with influenza viral M2 protein (ion channel). It blocks entry of protons into virion, prevents uncoating.
(a)
Compared with inactivated vaccines, mRNA vaccines primarily differ in that they:
A. Are incapable of inducing T-cell responses
B. Deliver antigen-encoding instructions rather than antigen itself
C. Require viral replication
D. Cannot be rapidly redesigned
E. Are less immunogenic
Why is selective toxicity more difficult to achieve with antiviral drugs than with antibiotics?
A. Viruses mutate less frequently
B. Viral enzymes are identical to host enzymes
C. Viruses lack genomes
D. Viruses rely heavily on host cellular machinery
E. Antivirals are always broad spectrum
Which antiviral drug class acts by preventing cleavage of viral polyproteins?
A. Entry inhibitors
B. Protease inhibitors
C. Neuraminidase inhibitors
D. Fusion inhibitors
E. Capsid stabilizers
A nucleoside analog antiviral drug must first be phosphorylated to become active. This requirement primarily:
A. Reduces specificity
B. Eliminates resistance
C. Enhances selectivity for infected cells
D. Increases toxicity
E. Bypasses viral polymerases
Which antiviral strategy is least effective once a cell is already infected?
A. Polymerase inhibition
B. Protease inhibition
C. Assembly inhibition
D. Release inhibition
E. Entry inhibition
Combination antiviral therapy is most effective because it:
A. Eliminates all side effects
B. Targets host immunity
C. Prevents antigenic shift
D. Reduces emergence of resistant mutants
E. Enhances vaccine efficacy
Which antiviral drug target is unique to retroviruses?
A. RdRp
B. Viral protease
C. Integrase
D. Neuraminidase
E. Capsid protein
Why are neuraminidase inhibitors effective specifically against influenza viruses?
A. Influenza replicates in the nucleus
B. Neuraminidase is essential for viral entry
C. They block viral transcription
D. Influenza lacks proofreading
E. They prevent release of progeny virions
Which factor most strongly contributes to antiviral drug resistance?
A. Host immune memory
B. Low viral replication rates
C. High-fidelity polymerases
D. Short treatment duration
E. High viral mutation rates
Which statement best summarizes the fundamental difference between antiviral drugs and viral vaccines?
A. Antivirals are broader in specificity
B. Vaccines act after infection
C. Antivirals induce immune memory
D. Vaccines target viral enzymes
E. Vaccines prevent infection; antivirals treat active replication
