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Microbiology > Lecture 10 > Flashcards

Lecture 10 Flashcards

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Biology 101 flashcards
1
Q

How is viral infection characterized?

A

By an incubation period

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2
Q

What happens during an incubation period?

A

The virus replicates within the host before disease symptoms and signs become evident

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3
Q

In synthetic events, what happens in the early stages?

A

Synthesis of viral enzymes required for nucleic acid replication

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4
Q

In synthetic events, what happens in the late stages?

A
  • Production of viral genome
  • Polypeptides
  • Processing of polypeptides and formation of infective virus
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5
Q

What are some examples of production of viral genome?

A
  • viruses with double stranded DNA synthesize mRNA just as the host cell does, using a DNA dependent RNA polymerase
  • RNA viruses must make their mRNA from RNA (if they are not mRNA), which involves a different mechanism
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6
Q

What are synthetic events?

A
  • replication
  • transcription
  • translation
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7
Q

There are a wide variety of virus types? Which type has the most viruses, DNA or RNA?

A

RNA has more

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8
Q

What is retrovirus (HIV) ?

A
  • RNA
  • Icosahedral
  • Enveloped virus
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9
Q

What is herpes virus?

A
  • DNA
  • Icosahedral
  • Enveloped virus
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10
Q

What is the difference between retrovirus and herpes virus?

A
  • retrovirus = RNA

* herpes virus = DNA

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11
Q

What is orthomyxovirus (Influenza)?

A
  • RNA
  • Helical
  • Enveloped virus
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12
Q

What does the assembly of enveloped viruses require?

A

Requires the association of nucleocapsid with cell membranes modified by viral glycoproteins

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13
Q

In assembly, what are some examples of subunits?

A
  • nucleic acid
  • structural proteins
  • enzymes
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14
Q

What does each subunit need to do?

A

They have to fit into compact arrangement to generate infectious virion.

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15
Q

What happens during release to non-enveloped viruses?

A

They are released by cell lysis

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16
Q

What happens during release to enveloped viruses?

A

They are released gradually by budding from plasma membrane or exocytosis.

17
Q

How do influenza virus act during release?

A

They are unique and have enzyme on their surface called neuraminidase (involved in release of progeny virions from host cells).

18
Q

What kind of damage can happen from viral infections?

A

Direct effects of viral replication on host cells via:

  • cytolytic damage
  • enhanced apoptosis
  • or damage due to host response to the infection

(side note: virus can make indirect damage)

19
Q

What are the events that happen during virus replication (viral growth curve)?

A

During a single infectious cycle:

  • following attachment, viral titer declines precipitously
  • eclipse: virus undergoes disassembly, transcription, translation, and genome replication
  • viral titer begins to increase as progeny virions, which are fully infectious, are assembled
20
Q

What are the 5 possible outcomes of viral infection? What is an example?

A
  • asymptomatic infection (resolution)
  • acute infection (influenza)
  • latency (herpes virus)
  • chronic infection (leading to immortalization, transformation of host cells to neoplasia, or cancer)
  • reactivation (episodic–HPV)
21
Q

Describe what happens in acute infections to a virus.

A

Virus undergoes multiple rounds of replication. It results in the death of the host cell. The number of virus particles produced in a single cell varies from a few for some viruses to thousands for others.

22
Q

Describe what happens in latent infection to a virus.

A

It does NOT result in the production of progeny virus.

Latent infections reflect the persistence of:

  • viral DNA either as an extra chromosomal element (herpes viruses)
  • as an integrated sequence within the host genome (retrovirus)
23
Q

What happens in reactivation to a virus?

A

At times (of poor control of infection due to compromised cell mediation immunity), reactivation of latent infection occurs.

24
Q

What happens in chronic infection to a virus?

A
  • virus particles continue to be shed after the period of acute illness
  • continues without death of the host cell or overt cellular injury
  • associated with host immune responses that are insufficient to clear the infection
  • may progress to cancer (example: chronic hepatitis becomes liver cancer)
25
Q

What is true about viruses?

A
  • viruses can cause asymptomatic infection
  • viruses have a latency period
  • viruses can cause chronic infections
  • there are both DNA and RNA viruses
26
Q

Continued: what is true about viruses?

A
  • following attachment, viral titers decreases
  • viral titers begin to increase as progeny virions are assembled
  • influenza viruses are unique and contains neuraminidase
  • synthesis of viral enzymes are required for nucleic acid replication
27
Q

How is a virus defined?

A

infectious particles that take over the operation of a cell for the purpose of multiplying

28
Q

How does a virus replicate?

A
  • gain access (attachment and entry)
  • convince cell to make new copies of the virus–the DNA is transcribed into RNA (replication)
  • the RNA is translated to produce the new virus (biosynthesis)
  • the new virus is assembled inside the host cell (assembly)
  • virus emerges from the host cell (release)
29
Q

What similar characteristics do viruses have?

A

They are specific in the types of cells they infect.

30
Q

What does specificity depend on?

A

On the types of receptors found on the cell. Every cell in the body has a pattern of protein receptors on the surface. The virus uses these proteins to target a specific cell for infection.

31
Q

Describe the DNA of a virus.

A

It is simple. It only contains the information needed to make new virus.

32
Q

When a new virus is translated during replication, where is the new virus?

A

It is still within the host cell

33
Q

When a virus is released from a host cell, what happens to the cell? (DNA virus)

A

The cell dies as they emerge. Sometimes the virus contains parts of the host cell that become the envelope of the virus.

34
Q

What does an envelope provide to a virus?

A

it provides some protection from the immune system of the host organism

35
Q

What do the new virus do after leaving the host cell?

A

They search out other cells to infect and replicate in.

36
Q

What is the target of anti-viral drugs?

A

They target specific points in the virus life cycle to prevent the virus from replicating.

Microbiology (10 decks)

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