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422 - Virology > Introduction > Flashcards

Introduction Flashcards

1
Q

Propagation of viruses depends on…

A

specialized host cells supplying the complex metabolic and biosynthetic machinery.

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2
Q

What do viruses lack?

A

Organelles

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3
Q

What is an example of a virus that has organelles that are not functional?

A

Arenavirus.

Have grainy particles that are ribosomes acquired from host cells. NOT FUNCTIONAL

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4
Q

What type of microscopy can be used to view viruses?

A

Electron microscopy or nanoscopy.

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5
Q

What family of viruses are the largest animal virus?

A

Pox viruses

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6
Q

What are the structural components of naked viruses?

A
  • Spike proteins
  • Capsid
  • Genome
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7
Q

What are the structural components of enveloped viruses?

A
  • Spike proteins
  • Protein capsid
  • Genome
  • Envelope
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8
Q

How does the presence of an envelope impact a virus?

A

The envelope serves as an extra layer of protection but since it is a lipid bilayer, it is more susceptible to degradation by detergents.

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9
Q

What is the function of the capsid?

A

A shell that protects the viral genome from nucleases.

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10
Q

The capsid is made up of…

A

Capsomeres (subunits of the protein coat).

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11
Q

What is the viral envelope derived from?

A

Host cell membranes (plasma or other).

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12
Q

Describe the features of the viral envelope.

A
  • Lipid bilayer
  • Studded with virus-coded glycoproteins
  • Closely surrounds virus-encoded membrane-associated proteins
  • Budding viruses carry certain host cell proteins that are constituents of the viral envelope
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13
Q

What part of the virus is glycosylated?

A

The outer capsid and the envelope proteins.

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14
Q

What is the importance of glycolsylation?

A

They are important in determining the host range and antigenic composition of the virion

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15
Q

What is the largest known virus?

A

Pithovirus sibericum (in amoeba)
1.5 micrometer

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16
Q

How do mimiviruses appear to be “mimicking microbes”?

A
  • Large size
  • Apparent gram-staining properties
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17
Q

What are bacteriophages?

A

Viruses that infect bacteria. These do not cause disease in animals.

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18
Q

What are the smallest viruses?

A

Circoviruses

Measures 17nm, only composed of 2 protein species

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19
Q

List the possible virus shapes.

A
  • Spherical
  • Dumbbell shaped
  • Bullet shaped
  • Helical

(I think there’s more?)

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20
Q

What kind of genetic material do circoviruses have?

A

Circular single-stranded DNA.

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21
Q

What are possible differences in viral genome?

A
  • DNA or RNA
  • Single coil or fragmented
22
Q

What is the implication of having a segmented genome in the virus?

A

Allows for more mistakes in packaging. Segments can get exchanged which can create additional subtypes. New subtypes can be created that can initiate new outbreaks.

23
Q

Why should viruses not be classified based on phylum or class?

A
  • Small genome
  • High rate of mutation

Both make it difficult to determine ancestry beyond order.

24
Q

What is the virus suffix to indicate order?

A

-virales

25
Q

What is the virus suffix to indicate family?

A

-viridae

26
Q

What is the virus suffix to indicate subfamily?

A

-virinae

27
Q

What is the virus suffix to indicate genus?

A

-virus

28
Q

What is the virus suffix to indicate Species?

A

-virus

29
Q

How many groups are in the Baltimore classification?

A

7

30
Q

What is the Baltimore classification based on?

A

Mechanism of mRNA production

31
Q

List the Baltimore classification groups.

A
  1. dsDNA viruses
  2. ssDNA viruses (+ sense DNA)
  3. dsRNA viruses
  4. (+)ssRNA viruses
  5. (-)ssRNA viruses
  6. ssRNA-RT viruses (+ sense RNA with DNA life cycle intermediate)
  7. dsDNA-RT viruses
32
Q

Name an example of a dsDNA virus?

A
  • Adeno
  • Herpes
  • Pox
33
Q

Name an example of a ssDNA virus?

A

Parvoviruses

34
Q

Name an example of a dsRNA virus?

A

Reoviruses

35
Q

Name an example of a (+)ssRNA virus?

A
  • Picornaviruses
  • Togaviruses
36
Q

Name an example of a (-)ssRNA virus?

A

Rhabdoviruses

37
Q

Name an example of a ssRNA-RT virus?

A

Retroviruses

38
Q

Name an example of a dsDNA-RT virus?

A

Hepadnaviruses

39
Q

Describe how (+) ssRNA produces mRNA.

A

The viral genome acts as mRNA and is translated to produce necessary proteins for mRNA replication. Then, those proteins are used to replicate the viral RNA.

ex. Picornaviruses

40
Q

Describe how (-) ssRNA produces mRNA.

A

Since the genome RNA is negative sense, it cannot be used for translation. The virus carries its own RNA dependent RNA polymerase (RdRp) to begin producing +ve sense mRNA from the genome template.

ex. Rhabdoviruses

41
Q

Describe how retroviruses produce mRNA.

A

Retroviruses carry the enzyme reverse transcriptase, which allows them to convert their ssRNA genome into dsDNA. The synthesized dsDNA is brought into the host cell nucleus where it is transcribed to mRNA by host cell enzymes (RNA polymerase II). In the nucleus, the viral DNA becomes incorporated into the host genome.

42
Q

What enzyme allows retroviruses to add their genome into the host cell genome?

A

Integrase enzyme

43
Q

Which viruses replicate in the nucleus?

A
  • Retroviruses
  • DNA viruses (except Pox virus)
  • Deltaviruses
44
Q

What enzyme produces mRNA from dsDNA?

A

RNA polymerase II

45
Q

Describe how ssDNA viruses produce mRNA.

A

Replication occurs in the nucleus since the virus requires cellular enzymes. The ssDNA is converted to dsDNA by the host’s DNA polymerase. Then, the dsDNA is converted to mRNA by the host cell’s RNA polymerase II.

ex. Parvoviruses

46
Q

Describe how dsDNA viruses produce mRNA.

A

These viruses enter the host cell nucleus and use the host’s RNA polymerase II to create mRNA.

47
Q

Describe how pox viruses produce mRNA.

A

Pox viruses are double stranded DNA viruses. However, they are unique since they are able to replicate and produce mRNA in the cytoplasm (rather than the nucleus) since it carries its own transcriptase enzyme which it uses to make mRNA.

47
Q

Why is it necessary to produce dsDNA from ssDNA?

A

The host cell machinery only recognizes dsDNA as a template to produce mRNA.

48
Q

Describe how special dsRNA viruses (pox, irido) produce mRNA.

A

The virus carries its own RNA dependent RNA polymerase (RdRp) to produce mRNA from the genome template.

49
Q

List the structural components of viruses and their functions.

A
  • Genome: Encoding information.
  • Capsid: Protecting the genome.
  • Envelope: Glycoproteins and lipid bilayer allow entry into host cell.

422 - Virology (7 decks)

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