Ch. 13- Study Bank Questions

Which of the following is not a characteristic of normal cells? A. They grow as a monolayer. B. They grow as multiple layers. C. They undergo a limited number of divisions and then die. D. They stick tightly to the surface of glass culture dishes.

B. They grow as multiple layers.

The site at which a virus has infected and subsequently lysed the infected cell, releasing its progeny to infect and lyse surrounding cells, thereby forming a "clear zone", is referred to as A. a burst area. B. a lyse area. C. a plaque. D. a dead zone.

C. a plaque

_____ may have a persistent infection AND may be a source of infection.

Carriers

_______ phage only infect E. coli that have pili.

Filamentous

_____ are made of protein only.

Prions

______ are an infectious protein.

Prions

_______ are unique in that they use RNA as a template to make DNA.

Retroviruses

The activation of the _____ system in a bacterium infected with a prophage results in complete lysis of the bacterial culture AND destruction of the viral repressor through host protease activity.

SOS

______ _______ involves the transfer of a few specific genes, utilizes a defective virus AND only involves genes near the viral DNA integration site.

Specialized transduction

T or F: A lysogenic cell contains viral DNA, a prophage, integrated into the host chromosome.

T

T or F: All viruses must separate the nucleic acid from the capsid before replication.

T

T or F: Filamentous virus is incapable of causing a lytic infection.

T

T or F: Naked and enveloped viruses both may enter the host via endocytosis.

T

T or F: Plant viruses may be passed from generation to generation of an insect vector.

T

T or F: The host range of a virus depends on the presence of host receptor molecules.

T

T or F: The integration of phage DNA into host DNA occurs in much the same fashion as seen in transformation, transduction or conjugation.

T

T or F: The restriction-modification system always has two genes involved, the cutting enzyme and the methylating enzyme.

T

T or F: Transduction often involves defective virus.

T

T or F: Virulent as well as temperate phages can serve as generalized transducing phages.

T

T or F: Viruses that cause acute infection result in productive infections.

T

T or F:The RNA phages contain only a single positive-sense strand of RNA.

T

______ _____ phages do not lyse the cells they invade because bacterial DNA has replaced critical viral DNA in the phage.

Transducing virulent

T or F: If a virus utilizes a lytic life cycle of reproduction, it will not induce tumors.

`T

Diseases of short duration frequently followed by long-term immunity are referred to as _____ infections.

acute

Genetic exchange in segmented viruses that allows a zoonotic virus to infect humans is termed

antigenic shift.

The correct order for the stages of a phage infection is:

attachment, penetration, transcription, replication of nucleic acid and protein, assembly, release

The changes that occur in virally-infected cells are characteristic for a particular virus and are referred to as the

cytopathic effect

If the infecting phage lacks some critical pieces of DNA necessary for replication it is called

defective

_____ phage is a virus that has lost some of its genetic material, and therefore cannot replicate within a new target cell.

defective

Viruses are commonly referred to by their _________ name.

disease & species

The common species name of the virus is based on the

disease the virus causes.

The replicative form of nucleic acid in filamentous phages is

dsDNA

If reasonably pure preparations of virus are available, the number of virus present may be determined by

electron microscopy

When an enveloped virus adsorbs to the host cell with its protein spikes, the virions are taken into the cell by the process of

endocytosis

The enveloped viruses typically obtain their______ from the host plasma membrane AND as they exit the host.

envelope

Phage-encoded _____ are produced in a sequential manner AND used to customize the cell for viral production.

enzymes

The viral envelope closely resembles the

eukaryotic cell membrane.

An exit method used by viruses which does not immediately destroy the host bacterium is

extrusion

What are two ways that phage can replicate in harmony (not directly lysing) their host cell?

extrusion & lysogeny

The bacterial viruses that are released by a process termed extrusion are called ______ phages.

filamentous

The best known chronic infection involves

hepatitis B

In the replication of phage containing positive-sense DNA, the ______ enzymes are used to make dsDNA.

host's

A ______ factor for viral infection is presence of specific receptor molecules on the host cell.

limiting

Cells infected with animal viruses ____ because functions necessary for cell survival are not carried out and the cell dies.

lyse

Phages that can either replicate and cause cell lysis or can integrate their DNA into the host DNA are called

lysogenic phages.

In the region of budding, the inside of the plasma membrane becomes coated with

matrix proteins.

Outside of living cells, viruses are

metabolically inert.

DNA is protected from restriction enzymes by being

methylated.

There are _______ families of RNA containing viruses that infect vertebrates.

14

In the case of T-even phages, the burst size is about

200 per host cell.

The time from absorption to release for T-even phage is about

30 minutes.

The term filterable viruses was coined by A. Beijerinck. B. Iwanowsky. C. Twort. D. d'Herelle.

A. Beijerinck

Why is it not surprising that AIDS patients frequently suffer a viral-induced tumor? A. HIV genomes integrate into the host cell chromosome. This integration might result in loss of control of the cell cycle (also known as cancer). B. The immune system's CD4+ T cells are directly responsible for elimination of tumor cells. HIV attacks them and eliminates them, making a person more susceptible to cancer. C. The therapies for HIV are highly mutagenic, which may lead to cancerous states in people taking the drug regimen. D. Products of an active HIV infection are highly mutagenic-so, as a person's illness progresses, these mutagenic compounds build up and are more capable of inducing a cancerous state.

A. HIV genomes integrate into the host cell chromosome. This integration might result in loss of control of the cell cycle (also known as cancer).

Why are viroids resistant to nucleases? A. Having a circular RNA 'genome,' they are resistant to the digestion of most exonucleases (that nibble/digest the free ends of RNA or DNA). B. Having a circular RNA 'genome,' with no protein shell, they are resistant to the protein-degrading activities of nucleases. C. Nucleases will only digest DNA, not RNA-so viroids are protected. D. Viroids have only been identified in plants. Plant nucleases cannot digest RNA.

A. Having a circular RNA 'genome,' they are resistant to the digestion of most exonucleases (that nibble/digest the free ends of RNA or DNA).

Which is a filamentous phage? A. M13 B. T4 C. lambda D. phi X174

A. M13

The family to which the Rhinovirus belongs is the A. Picornaviridae. B. Enterovirus. C. Enteroviridae. D. Picornavirus.

A. Picornaviridae.

You add an unknown phage to a mixture of F+ and F- cells of E. coli and plate out the bacteria. The bacterial colonies that grow are all F-. How can you explain this phenomenon? A. The phage bound to a receptor on the sex pilus, and therefore only infected the F+ cells (leaving the F- cells alone). B. The phage bound to a receptor on the F- cells, leaving only them alive and allowing the F+ cells to die off. C. The phage integrated (lysogenized) the F- cells, giving them a selective advantage over the F+ cells. D. F+ cells are uniquely susceptible to phage attack for unknown reasons.

A. The phage bound to a receptor on the sex pilus, and therefore only infected the F+ cells (leaving the F- cells alone).

The integration of phage DNA into the bacterial chromosome occurs because of A. identical DNA sequences in both. B. the phage's ability to synthesize enzymes to enter the bacterium. C. similar RNA nucleotides in both. D. the similarity in enzyme metabolism. E. the phage's ability to synthesize enzymes to enter the bacterium AND similar RNA nucleotides in both.

A. identical DNA sequences in both.

The term "segmented" refers to viruses that A. may contain several pieces of RNA. B. have an icosahedral-shaped capsid. C. are linked together before budding out. D. have an envelope.

A. may contain several pieces of RNA.

The approximate viral concentration of a sample may be determined by A. quantal assay. B. endpoint assay. C. the titer. D. the lysate assay.

A. quantal assay

After growth in tissue culture, the infected cells lyse and the virus may be harvested from A. the liquid supernatant after centrifugation, the lysate. B. the remainder. C. the quantal layer. D. the monolayer.

A. the liquid supernatant after centrifugation, the lysate.

Animal viruses are divided into a number of families whose names end in A. -virus. B. -viridae. C. -viscous. D. -eieio.

B. -viridae.

The nucleocapsid is composed of A. DNA and RNA and protein. B. DNA or RNA and protein. C. protein located in the nucleus. D. nucleic acid in the ribosome.

B. DNA or RNA and protein.

Explain why HIV becomes resistant so quickly when a single drug is used therapeutically. A. The virus is an RNA genome virus-by using host RNA polymerase to directly copy the genome to make more virus particles, there's no proofreading capability. This leads to a high rate of mutation of the viral genome and increased chance for drug resistance. B. HIV utilizes reverse transcriptase to make a cDNA version of its RNA genome. This polymerase is 'sloppy,' with a high rate of error and lack of a proofreading capability. This leads to a high rate of mutation of the viral genome and increased chance for drug resistance. C. HIV synthesizes a protein enzyme that directly cleaves anti-HIV drugs, giving it a characteristically high rate of resistance to a single drug type. D. HIV is constantly changing its genetic structure by swapping genetic elements with other virus strains. This leads to a high rate of mutation of the viral genome and increased chance for drug resistance.

B. HIV utilizes reverse transcriptase to make a cDNA version of its RNA genome. This polymerase is 'sloppy,' with a high rate of error and lack of a proofreading capability. This leads to a high rate of mutation of the viral genome and increased chance for drug resistance.

Most temperate phages integrate into the host chromosome, whereas some replicate as plasmids. Which kind of relationship do you think would be more likely to maintain the phage in the host cell, and why? A. Plasmids-they're smaller, so they'd be easier to replicate by the host cell. B. Integrated-the host cell would be less likely to view this DNA as 'foreign' on subsequent rounds of replication, and would retain it more easily. C. Plasmids-these structures often carry other genes that may give the host cell a selective advantage over cells that don't have them. D. Integration-because plasmids are frequently lost in the first round of binary fission, which could leave a cell without the virus genome.

B. Integrated-the host cell would be less likely to view this DNA as 'foreign' on subsequent rounds of replication, and would retain it more easily.

Would ID50 and LD50 necessarily be the same for a given virus? Why or why not? A. Yes, because the number of viruses that infect 50% of a test population should also kill 50% of that test population. B. No, because a virus may be highly infectious (very low ID50 value) but only marginally lethal (very high LD50 value). A prime example of this is the rhinovirus (common cold virus). C. No, because very few viruses are lethal, yet many are highly infectious. The 2 values should ALWAYS be different. D. Yes, because what we're actually describing here is infection/killing of individual CELLS, not of entire organisms. If a cell is infected, it will always be killed.

B. No, because a virus may be highly infectious (very low ID50 value) but only marginally lethal (very high LD50 value). A prime example of this is the rhinovirus (common cold virus).

An antibiotic is added to a culture of E. coli, resulting in death of the cells. Bacteriophage are then added. Would the phage replicate in the E. coli cells? Why or why not? A. Yes, because the machinery inside the cells is most likely still active, even though the cells are no longer living. The virus could use that machinery to replicate new virus particles. B. No, because the virus would depend too much on having the active machinery of a living cell for its replication. Without the ability of the cell to try to replace what is lost/damaged/used as the virus goes through its life cycle, the virus couldn't reproduce effectively. C. Yes, because viruses are capable of reanimating dead cells to force them to produce more virus particles. D. No, because entry of the virus into the target cell is dependent on the cell being alive to conduct endocytosis of the virus.

B. No, because the virus would depend too much on having the active machinery of a living cell for its replication. Without the ability of the cell to try to replace what is lost/damaged/used as the virus goes through its life cycle, the virus couldn't reproduce effectively.

Would you expect the number of virions to be the same if you measured them by the plaque assay or by counting using the electron microscope? Why? A. Yes-both methods measure the total number of virus particles in a solution. B. No-the plaque assay only measures viable virus particles, while the electron microscope cannot distinguish between defective and viable virus. C. No-you cannot count virus particles by using a plaque assay. You can only get a relative difference in quantity from one preparation of virus particles to another with this method. D. Yes-only fully functioning viruses will be released from a host cell, so the quantified number of virus particles in a plaque assay should be identical to the number of free virus particles counted by electron microscopy within a given preparation.

B. No-the plaque assay only measures viable virus particles, while the electron microscope cannot distinguish between defective and viable virus.

What part of the E. coli T4 phage attaches to the host cell receptors? A. Capsid fragments around the nucleic acid. B. Protein fibers at the end of the phage tail. C. Pili of the envelope. D. Spikes of the envelope.

B. Protein fibers at the end of the phage tail.

Crystallization of Tobacco Mosaic Virus was accomplished by A. Berkley. B. Stanley. C. Iwanowsky. D. Twort.

B. Stanley

One of the most intensively studied virulent phages which infects E. coli is A. T9. B. T4. C. beta. D. gamma.

B. T4.

Plant viruses may be transmitted by A. worms. B. contaminated seeds. C. humans. D. insects. E. All of the choices are correct.

E. All of the choices are correct.

Using phages to treat a bacterial infection is an interesting idea because A. a single type of phage can destroy a wide range of strains of the same pathogen. B. of the increasing problem of antibiotic resistance. C. lysed bacteria pose no threat. D. a single phage can be genetically engineered to infect many different species of bacteria.

B. of the increasing problem of antibiotic resistance.

Viroids cause disease in A. animals. B. plants. C. bacteria. D. fungus.

B. plants.

During penetration of E. coli by the T4 phage A. lysozyme is used to allow entry of the phage capsid. B. the tail acts as a "hypodermic needle", injecting the phage DNA into the cell. C. the protein fibers digest a hole in the cell wall. D. the bacterial receptor molecules open a hole through the cell wall.

B. the tail acts as a "hypodermic needle", injecting the phage DNA into the cell.

Why do animal viruses have envelopes and phages rarely do? A. Since bacteria don't have cell membranes, the bacterial viruses (phages) don't pick them up when they leave the target cells. B. Phages acquire an outer surrounding that is a part of the cell wall of the bacterium they were created in, rather than an outer surrounding of plasma membrane. C. Animal viruses will often utilize the envelope in order to fuse with the plasma membrane of a new target cell, gaining entry into the cytoplasm. D. Animal viruses build the envelope inside of the target cell as they are being replicated, but before the cell breaks open and releases them into the extracellular environment. The envelope is a remnant of this building process.

C. Animal viruses will often utilize the envelope in order to fuse with the plasma membrane of a new target cell, gaining entry into the cytoplasm.

Is antigenic shift alone likely to lead to influenza pandemics? A. Yes-ONLY antigenic shift can lead to the large-scale mixing of gene elements required to produce a pandemic flu strain. B. No-ONLY antigenic DRIFT can lead to the large-scale mixing of gene elements required to produce a pandemic flu strain. C. Perhaps-but it would most likely be a mixture of antigenic shift AND drift that would result in a pandemic strain. D. No-antigenic SHIFT is responsible for changes in the hemagglutinin protein, while antigenic DRIFT is responsible for changes in the neuraminidase protein. You must have changes in both to lead to a pandemic strain.

C. Perhaps-but it would most likely be a mixture of antigenic shift AND drift that would result in a pandemic strain.

Transmission of plant viruses by insects can occur from A. viruses associated with insect mouth parts. B. viruses circulating but not multiplying in the insect's body. C. viruses that multiply within the body of the insect. D. All of the above

D. All of the above

Most phages that contain single-stranded DNA A. are extruded. B. contain a positive-sense DNA strand. C. have their DNA transformed to double-stranded DNA before replication and transcription occur. D. All of the choices are correct.

D. All of the choices are correct.

Once inside the host cell, phage DNA A. is replicated. B. is transcribed. C. may get degraded by bacterial nucleases. D. All of the choices are correct.

D. All of the choices are correct.

Regarding phage replication, A. the majority of phages are temperate. B. when integrated into host DNA, the phage DNA is called a prophage. C. lambda is a good example of a temperate phage. D. All of the choices are correct.

D. All of the choices are correct.

Spongiform encephalopathy occurs in A. humans. B. cattle. C. sheep. D. All of the choices are correct.

D. All of the choices are correct.

Which does not refer to the shape of a virus? A. icosahedral (isometric) B. helical C. complex D. bacillus

D. bacillus

Bacteria infected with filamentous phages are termed A. temperate cells. B. plaque-producing cells. C. virulent strains. D. carrier cells.

D. carrier cells.

Bacteriophages and animal viruses A. both may enter a host cell by endocytosis. B. both may enter a host cell by fusion. C. both involve entry of the entire nucleocapsid. D. differ because bacteriophages leave the capsid outside the cell, while animal virus entry involves the entry of the whole nucleocapsid.

D. differ because bacteriophages leave the capsid outside the cell, while animal virus entry involves the entry of the whole nucleocapsid.

Resistance of some animals to certain viral diseases is based on A. lack of spikes for attachment. B. phagocytosis of the virus by the host cell. C. the presence of the viral envelope. D. lack of specific receptors on the host cell.

D. lack of specific receptors on the host cell.

The phenomenon responsible for the ability of Corynebacterium diphtherium to produce the virulent toxin responsible for the devastating effects of diphtheria is called A. self-assembly. B. matrix conversion. C. prion protein. D. lysogenic conversion.

D. lysogenic conversion.

One group of animal viruses that are able to agglutinate red blood cells are the A. coronavirus. B. retrovirus. C. reovirus. D. myxovirus.

D. myxovirus

Prions affect the A. respiratory system. B. gastrointestinal tract. C. nervous system. D. lymphatic system.

D. nervous system.

An infection in which the virus is continually present in the body is referred to as A. acute. B. balanced. C. determinant. D. persistent.

D. persistent.

For which of the following processes are enzymes not required? A. replication B. translation C. maturation D. self-assembly

D. self-assembly

Prions A. replicate by converting normal host proteins into prion proteins. B. responsible for "Mad Cow Disease" can cause a similar disease in humans. C. can be transmitted by consumption of dried or cooked food. D. that cause Spongiform Encephalopathy have the same amino acids but different folding properties from PrPc. E. All of the above

E. All of the above

Why is it virtually impossible to stamp out a disease caused by a zoonotic virus? A. You'd have to drive the vector organism extinct to do so. B. Many vector organisms have multiple stages of their life cycle that can carry a zoonotic virus, which complicates controlling the vector-borne transmission. C. Many viruses transmitted in this manner may utilize more than one vector organism. D. Many zoonotic viruses may be able to reside in more than 1 host organism, complicating control measures. E. All of the above are correct.

E. All of the above are correct.

A mutation in E. coli results in the loss of both restriction endonucleases and modification enzymes. Would you expect any difference in the frequency of gene transfer via transduction FROM Salmonella INTO this E. coli strain? A. No-since the Salmonella strain is normal, the rate of production of transducing virus particles would still be the same, resulting in the same frequency of gene transfer. B. Yes-the loss of the restriction endonucleases would leave the recipient E. coli unable to break down 'invading' viral DNA from the transducing phage. This would lead to higher rates of successful transduction. C. Yes-the loss of the modification enzymes would leave the recipient E. coli unable to tag its own DNA as 'self,' leaving the viral DNA untagged and recognizable as 'foreign,' and targeted for destruction. This would lead to higher rates of successful transduction. D. No-transduction efficiency isn't affected by either restriction endonucleases or modification enzymes, so there'd be no effect on the overall rate. E. Yes-the loss of the restriction endonucleases would leave the recipient E. coli unable to break down 'invading' viral DNA from the transducing phage, AND the loss of the modification enzymes would leave the recipient E. coli unable to tag its own DNA as 'self,' leaving the viral DNA untagged and recognizable as 'foreign,' and targeted for destruction. Together, these would lead to higher rates of successful transduction.

E. Yes-the loss of the restriction endonucleases would leave the recipient E. coli unable to break down 'invading' viral DNA from the transducing phage, AND the loss of the modification enzymes would leave the recipient E. coli unable to tag its own DNA as 'self,' leaving the viral DNA untagged and recognizable as 'foreign,' and targeted for destruction. Together, these would lead to higher rates of successful transduction.

The receptors to which animal virus attachment proteins usually bind are A. proteins. B. carbohydrates. C. nucleic acid. D. lipids. E. glycoproteins.

E. glycoproteins.

The best-known examples of viruses that cause latent infections are A. polio. B. herpes. C. measles. D. chickenpox. E. herpes AND chickenpox.

E. herpes AND chickenpox.

Cells taken from a tumor A. may be used to grow viruses. B. can be cultivated in vitro indefinitely. C. may be used to grow bacteriophages. D. divide 50 times and then die. E. may be used to grow viruses AND can be cultivated in vitro indefinitely.

E. may be used to grow viruses AND can be cultivated in vitro indefinitely.

Assembly of the T4 phage... A. may involve some self-assembly. B. may involve the use of scaffolds. C. is completely self-assembly. D. is completely dependent on scaffolds. E. may involve some self-assembly AND may involve the use of scaffolds.

E. may involve some self-assembly AND may involve the use of scaffolds.

Viruses A. probably keep the numbers of bacteria in check. B. have no effect on the number of bacteria. C. increase the number of bacteria. D. are active in passing DNA from one bacterium to another. E. probably keep the numbers of bacteria in check AND are active in passing DNA from one bacterium to another.

E. probably keep the numbers of bacteria in check AND are active in passing DNA from one bacterium to another.

During attachment of phage to E. coli, the phage A. actively seek out the bacteria. B. randomly bump into the bacteria. C. attach to proteins or carbohydrates on the bacterial surface. D. attach to the bacterial RNA. E. randomly bump into the bacteria AND attach to proteins or carbohydrates on the bacterial surface.

E. randomly bump into the bacteria AND attach to proteins or carbohydrates on the bacterial surface.

In the region of budding, the plasma membrane becomes involved with A. carbohydrates. B. spike proteins. C. matrix proteins. D. enzymes. E. spike proteins AND matrix proteins.

E. spike proteins AND matrix proteins.

_____ viruses have an outer lipid bilayer membrane containing various proteins.

Enveloped

T or F: All single-stranded DNA phages are extruded.

F

T or F: Bacteriophage, unlike animal viruses, often have special viral-specific enzymes carried in the capsid which enter the host cell at the same time as the nucleic acid.

F

T or F: Capsids are made of a number of capsomeres which are covalently bonded to one another.

F

T or F: Completed filamentous phages are often found in the cytoplasm of infected bacteria.

F

T or F: Electron microscopy is useful for counting viruses and distinguishing between infective and non-infective virions.

F

T or F: Infective and non-infective viruses may be distinguished by growth on MacConkey's agar.

F

T or F: The structure of plant, animal and bacterial viruses are each, fundamentally, very different from one another.

F

The concentration of virus that infects or kills 50% of the host cells is referred to as the

LD50 AND ID50.

_______ cells are immune to infection by the same virus AND may have new properties.

Lysogenized

Viruses that infect bacteria are referred to as

bacteriophages

Viruses may not be cultivated in

blood agar

In addition to lysis, animal viruses may exit the host cell by

budding

A key feature of all viral infections is the separation of viral nucleic acid from the ______.

capsid

The shape of the virus is determined by its

capsid

Normal tissue taken from animals and prepared immediately as media for viral growth is termed a(n)

primary culture

Once integrated, phage DNA can remain in the _____ state as long as certain phage genes are repressed.

prophage

The _____ _____ of a virus is called a capsid, protects the nucleic acid AND is involved in recognition of host cell receptors.

protein coat

Phage-encoded ______ are coded for by phage DNA AND early proteins.

proteins

There are _______ families of DNA containing viruses that infect vertebrates.

seven

The terms isometric, icosahedral and pleomorphic refer to _____ of viruses.

shapes

The filamentous phages all contain

single-stranded DNA.

Attachment of animal viruses to the host cell may be by means of

spikes

The protein projections on the surface of a virus that are involved in attachment to the host cell are called

spikes

The genome of retroviruses is made of

ssRNA

Viroids characteristically are composed of

ssRNA

RNA phages usually contain

ssRNA.

A ______ phage may be lysogenic AND enters a lysogenic or lytic life cycle shortly after entering the host cell.

temperate

What part of the attached bacteriophage enters through the host cell wall?

the nucleic acid

A ___ is a complete, extracellular virus particle.

virion

A ______ is composed of protein, either RNA or DNA, and possibly lipid.

virion

In latent infections, the____ are only produced during reactivation.

virions

A phage that replicates inside the host cell and then lyses its host during its release is a

virulent or lytic phage.

Plant viruses enter the host plant via

wound sites.