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Biology Of The Cell > Week 10: Bacteriophages And Viruses > Flashcards

Week 10: Bacteriophages And Viruses Flashcards

1
Q

What is a virus?

A

Genetic elements that can multiply their genome independently of a cell’s chromosome but require a host.

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2
Q

What is a ‘naked’ virus?

A

A virus that consists of a nucleocapsid, which is composed of a capsid and nucleic acid.

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3
Q

What are adenoviruses responsible for?

A

A large number of upper respiratory infections.

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4
Q

What shape does the capsid of adenovirus form?

A

An icosahedron.

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5
Q

What is a characteristic of enveloped viruses?

A

They have a lipid bilayer that comes from the host cell.

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6
Q

What are examples of enveloped viruses?

A
  • Influenza virus
  • Herpes virus
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7
Q

What are complex viruses?

A

Viruses like bacteriophage T4 that have a more intricate structure.

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8
Q

What types of genomes can viral genomes consist of?

A
  • DNA
  • RNA
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9
Q

What are the categories of RNA viruses?

A
  • ssRNA
  • dsRNA
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10
Q

What is the lytic pathway of infection?

A

All resources of the host cell are used to produce phage particles, leading to the cell being lysed.

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11
Q

What type of life cycle can bacteriophage λ enter?

A

Lysogenic or lytic life cycle.

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12
Q

What influences the decision between the lysogenic and lytic cycle?

A

A transcriptional regulatory network.

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13
Q

What happens during early gene expression in virus infection?

A

Discrimination between ‘early’ and ‘late’ genes that are expressed.

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14
Q

What is the role of cI protein in bacteriophage λ?

A

It represses transcription of the genes for lysis and establishes expression of the lysogenic genes.

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15
Q

What occurs if a second phage injects its chromosome into an already infected cell?

A

cI binds to PRM, preventing production of the replication proteins of the second phage genome.

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16
Q

What is the result of cII protein being at a low level?

A

Transcription of Cro is not repressed, leading to the establishment of the lytic cycle.

17
Q

What can cause reactivation of latent herpes simplex virus (HSV)?

A
  • Stress
  • UV light
  • Trauma
  • Fever
18
Q

What can happen following the integration of retroviral genomes into the host genome?

A

It can cause tumor formation and other cancers.

19
Q

What are the steps for double-stranded DNA viruses during replication?

A
  • Transcription of dsDNA into mRNA
  • Transport into nucleus
  • Translation
20
Q

What is the difference between prokaryotic and eukaryotic cell infection processes?

A

Prokaryotic cells have no compartmentation, whereas eukaryotic cells do, requiring transport into the nucleus.

21
Q

What is a common complication of herpes simplex virus (HSV) infection?

A

HSV encephalitis, which can lead to severe brain damage or death.

22
Q

Fill in the blank: The viral genome of HIV-1 integrates into the host genome, which can remain dormant for _______ with very low virus titres.

A

years.

23
Q

What is HSV encephalitis?

A

A rare but dramatic condition caused by herpes simplex virus that can lead to fever, seizures, paralysis, coma, and severe brain damage or death.

24
Q

What virus causes chickenpox?

A

Varicella-Zoster Virus (VZV)

25
Q

How does chickenpox relate to HSV?

A

Chickenpox is caused by a virus closely related to HSV and both viruses remain in the nervous system.

26
Q

What percentage of chickenpox cases may recur as zoster or shingles?

A

About 10%

27
Q

What is a common problem with virus replication?

A

Replication of viruses is surprisingly inaccurate.

28
Q

Which type of viruses show very high error rates in replication?

A

RNA viruses

29
Q

What are two challenges viruses face when growing in a host?

A

Viruses have to replicate very quickly and escape the immune system of the host.

30
Q

What effect does high error rates during replication have on viruses?

A

It ensures variation of the outer surface proteins.

31
Q

True or False: HSV encephalitis occurs more often as a primary infection than as a re-activation.

A

False

32
Q

Fill in the blank: Chickenpox is caused by the _______.

A

Varicella-Zoster Virus (VZV)

Biology Of The Cell (23 decks)

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