Question 1

An antibiotic is added to a culture of E. coli, resulting in death of the cells. Bacteriophages are then added. Would the phages replicate in the E. coli cells? Why or why not?

Accepted Answer

A)   Yes, because the cellular machinery of the bacteria is most likely still active. The bacteriophages could use that machinery to replicate new virus particles.
B)   No, because the bacteriophages would depend too much on having the active machinery of a living host cell for replication.
C)   Yes, because bacteriophages are capable of reanimating dead cells to force them to produce more virus particles.
D)   No, because entry of the bacteriophages into the target cell is dependent on the cell being alive to conduct endocytosis of the virus.
E)   No, because dead E. coli cells do not have any receptors on their cell walls to which the bacteriophages can attach for entry into the host cell by fusion.F) A) and E)
G) C) and D)

Question 2

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

Accepted Answer

A)   extrusion.
B)   budding.
C)   fission.
D)   fusion.
E)   endocytosis.F) B) and E)
G) None of the above

Question 3

Carriers

Accepted Answer

A)   may have a persistent infection.
B)   may be a source of infection.
C)   usually show symptoms of the disease AND may be a source of infection.
D)   have been cured of the infection.
E)   may have a persistent infection AND may be a source of infection.F) A) and D)
G) A) and B)

Question 4

Plant viruses enter the host plant via

Accepted Answer

A)   wound sites.
B)   specific receptors.
C)   nonspecific receptors.
D)   seeds.
E)   endocytosis.F) D) and E)
G) C) and D)

Question 5

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) , for example the rhinovirus (common cold virus) .
C)   No, because very few viruses are lethal, yet many are highly infectious. The two values should ALWAYS be different.
D)   Yes, because what we're actually describing here is the infection/ killing of individual cells, not of entire organisms. If a cell is infected, it will always be killed.
E)   Yes, because ID50 and LD50 are actually measurements of the same thing: effectiveness of a virus in entering and damaging a host cell.F) C) and D)
G) C) and E)

Question 6

Phage-encoded enzymes are

Accepted Answer

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

Question 7

The shape of the virus is determined by its

Accepted Answer

A)   nucleic acid.
B)   capsid.
C)   envelope.
D)   tail.
E)   spikes.F) A) and B)
G) A) and C)

Question 8

If you had three tubes of flu viruses and you exposed tube 1 to protease, tube 2 to protease and RNase, and tube 3 to protease and DNase, and the contents of tube 2 were be degraded, you would be able to conclude that

Accepted Answer

A)   an RNA virus.
B)   a DNA virus.
C)   a protein virus.
D)   resistant to proteases.
E)   an opportunist.F) B) and D)
G) None of the above

Question 9

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

Accepted Answer

A)   1 day.
B)   30 minutes.
C)   10 minutes.
D)   1 minute.
E)   45 seconds.F) A) and C)
G) A) and B)

Question 10

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

Accepted Answer

A)   penetration.
B)   production.
C)   endocytosis.
D)   fusion.
E)   budding.F) B) and E)
G) None of the above

Question 11

Entry of bacteriophages and animal viruses into host cells

Accepted Answer

A)   is by endocytosis.
B)   is by fusion.
C)   involve entry of the entire nucleocapsid.
D)   differs because bacteriophages leave the capsid outside the cell, while animal virus entry involves the entry of the whole nucleocapsid.
E)   differs because animal viruses leave the capsid outside the cell, while bacteriophage entry involves the entry of the whole nucleocapsid.F) C) and E)
G) A) and B)

Question 12

A virion is composed of

Accepted Answer

A)   lipid, protein, and either RNA or DNA.
B)   protein, either RNA or DNA, and possibly lipid.
C)   protein and either RNA or DNA, but no lipid.
D)   protein and both RNA and DNA, but no lipid.
E)   protein, and possibly lipid.F) A) and D)
G) A) and C)

Question 13

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)   These are all characteristics of normal cells.F) A) and C)
G) All of the above

Question 14

A key feature of all viral infections is the

Accepted Answer

A)   integration of viral DNA into host DNA.
B)   separation of viral nucleic acid from the capsid.
C)   disintegration of host DNA.
D)   addition of a lipid membrane to the virus.
E)   lysis of the host cell.F) A) and B)
G) B) and E)

Question 15

The correct order for the stages of a phage infection is

Accepted Answer

A)   penetration, transcription, attachment, replication of nucleic acid and protein, assembly, release.
B)   attachment, penetration, transcription, replication of nucleic acid and protein, assembly, release.
C)   attachment, replication of nucleic acid and protein, penetration, transcription, assembly, release.
D)   transcription, attachment, replication of nucleic acid and protein, assembly, penetration, release.
E)   attachment, replication of nucleic acid and protein, assembly, penetration, transcription, release.F) A) and B)
G) A) and C)

Question 16

You tell your friend that you are happy to be receiving your vaccination because hepatitis B is associated with hepatocellular carcinoma (liver cancer) . Select the FALSE statement regarding viruses and cancer.

Accepted Answer

A)   Viruses that lead to cancer formation are called oncogenic viruses.
B)   The most common viral causes of tumors are certain DNA viruses such as hepatitis B virus.
C)   Some viruses carry an oncogene-infection with these viruses interferes with the host cell's own growth-control mechanisms.
D)   The majority of tumors are caused by oncogenic viruses but some may be caused by mutations in host genes that regulate cell growth.
E)   Viruses that insert their genome into the host cell's chromosome may cause changes at the insertion site, converting a proto-oncogene into an oncogene.F) A) and D)
G) A) and E)

Question 17

The viral envelope closely resembles the

Accepted Answer

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

Question 18

A lysogen is

Accepted Answer

A)   a bacteriophage that carries bacterial DNA integrated into its genome.
B)   an insect that carries virus DNA in its genome.
C)   a temperate phage that can insert its DNA into the host's DNA.
D)   a bacterium that carries phage DNA (a prophage)  integrated into its genome.
E)   a bacteriophage that lyses its host as a result of its replication cycle.F) C) and D)
G) A) and C)

Question 19

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

Accepted Answer

A)   polio AND herpes.
B)   herpes AND measles.
C)   measles AND chickenpox.
D)   chickenpox AND polio.
E)   herpes AND chickenpox.F) A) and C)
G) B) and E)

Question 20

A limiting factor for viral infection of animals cells is

Accepted Answer

A)   presence of specific receptor molecules on the host cell.
B)   internal metabolic temperature of the host cell.
C)   nutrition of the host cell.
D)   stage of cell cycle of the host cell.
E)   culture conditions of the host cell.F) B) and D)
G) A) and B)

Exam 13: Viruses, Viroids, and Prions

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

The shape of the virus is determined by its

Correct AnswerverifiedShow Answer

Phage-encoded enzymes are

Correct AnswerverifiedShow Answer

A key feature of all viral infections is the

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

The viral envelope closely resembles the

Correct AnswerverifiedShow Answer

If you had three tubes of flu viruses and you exposed tube 1 to protease, tube 2 to protease and RNase, and tube 3 to protease and DNase, and the contents of tube 2 were be degraded, you would be able to conclude that

Correct AnswerverifiedShow Answer

A lysogen is

Correct AnswerverifiedShow Answer

You tell your friend that you are happy to be receiving your vaccination because hepatitis B is associated with hepatocellular carcinoma (liver cancer) . Select the FALSE statement regarding viruses and cancer.

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

A virion is composed of

Correct AnswerverifiedShow Answer

The correct order for the stages of a phage infection is

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

A limiting factor for viral infection of animals cells is

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Entry of bacteriophages and animal viruses into host cells

Correct AnswerverifiedShow Answer

An antibiotic is added to a culture of E. coli, resulting in death of the cells. Bacteriophages are then added. Would the phages replicate in the E. coli cells? Why or why not?

Correct AnswerverifiedShow Answer

Carriers

Correct AnswerverifiedShow Answer

Plant viruses enter the host plant via

Correct AnswerverifiedShow Answer

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