Question 1

Which of the following is not a characteristic of normal cells?

Accepted Answer

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.E) A) and D)
F) None of the above

Question 2

Carriers

Accepted Answer

A)  may have a persistent infection.
B)  may be a source of infection.
C)  usually show symptoms of the disease.
D)  have been cured of the infection.
E)  may have a persistent infection AND may be a source of infection.F) All of the above
G) None of the above

Question 3

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?

Accepted Answer

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.E) A) and D)
F) B) and C)

Question 4

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

Accepted Answer

A)  a tail.
B)  the envelope.
C)  a capsid.
D)  spikes.E) None of the above
F) B) and C)

Question 5

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

Accepted Answer

A)  two
B)  five
C)  seven
D)  fourteenE) None of the above
F) C) and D)

Question 6

The best-known examples of viruses that cause latent infections are

Accepted Answer

A)  polio.
B)  herpes.
C)  measles.
D)  chickenpox.
E)  herpes AND chickenpox.F) All of the above
G) A) and B)

Question 7

The term filterable viruses was coined by

Accepted Answer

A)  Beijerinck.
B)  Iwanowsky.
C)  Twort.
D)  d'Herelle.E) B) and D)
F) A) and C)

Question 8

The viral envelope closely resembles the

Accepted Answer

A)  prokaryotic cell wall.
B)  capsomere.
C)  eukaryotic cell membrane.
D)  cytoplasm.E) A) and B)
F) A) and C)

Question 9

The filamentous phages all contain

Accepted Answer

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

Question 10

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

Accepted Answer

A)  photocolorimetry.
B)  gas chromatography.
C)  light microscopy.
D)  electron microscopy.E) C) and D)
F) A) and B)

Question 11

Animal viruses are divided into a number of families whose names end in

Accepted Answer

A)  -virus.
B)  -viridae.
C)  -viscous.
D)  -eieio.E) All of the above
F) A) and C)

Question 12

Cells taken from a tumor

Accepted Answer

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.F) A) and C)
G) A) and E)

Question 13

Prions affect the

Accepted Answer

A)  respiratory system.
B)  gastrointestinal tract.
C)  nervous system.
D)  lymphatic system.E) A) and B)
F) A) and C)

Question 14

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

Accepted Answer

A)  1 minute.
B)  10 minutes.
C)  30 minutes.
D)  1 day.E) B) and D)
F) A) and C)

Question 15

Viruses

Accepted Answer

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.F) B) and C)
G) None of the above

Question 16

Completed filamentous phages are often found in the cytoplasm of infected bacteria.

Accepted Answer

A) True 
 B)False

Question 17

Viroids cause disease in

Accepted Answer

A)  animals.
B)  plants.
C)  bacteria.
D)  fungus.E) All of the above
F) A) and D)

Question 18

Phage-encoded enzymes are

Accepted Answer

A)  all produced simultaneously.
B)  produced in a sequential manner.
C)  strictly host enzymes.
D)  used to customize the cell for viral production.
E)  produced in a sequential manner AND used to customize the cell for viral production.F) A) and D)
G) A) and C)

Question 19

Would ID50 and LD50 necessarily be the same for a given virus? Why or why not?

Accepted Answer

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.E) A) and B)
F) A) and D)

Question 20

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.

Accepted Answer

A) True 
 B)False

Exam 13: Viruses, Viroids and Prions

Prions affect the

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The term filterable viruses was coined by

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

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Which of the following is not a characteristic of normal cells?

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Cells taken from a tumor

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Carriers

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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.

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The best-known examples of viruses that cause latent infections are

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Viruses

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Animal viruses are divided into a number of families whose names end in

Correct AnswerverifiedShow Answer

Would ID50 and LD50 necessarily be the same for a given virus? Why or why not?

Correct AnswerverifiedShow Answer

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?

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Completed filamentous phages are often found in the cytoplasm of infected bacteria.

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Viroids cause disease in

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The filamentous phages all contain

Correct AnswerverifiedShow Answer

Phage-encoded enzymes are

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

The viral envelope closely resembles the

Correct AnswerverifiedShow Answer

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Would ID₅₀ and LD₅₀ necessarily be the same for a given virus? Why or why not?

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