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BM211: Introduction to Microbiology > Block D Lecture 1: Introduction to Virology > Flashcards

Block D Lecture 1: Introduction to Virology Flashcards

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Biology 101 flashcards
1
Q

How did viruses used to be classified?

A

By the disease type they cause
(Slide 2)

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2
Q

What are the 5 different classes in disease based virial classification?

A

Enteric viruses
Arboviruses
Respiratory viruses
Hepatitis viruses
Sexually transmitted viruses

(REMEMBER EARTHS WITHOUT THE T - EARHS)
(Slide 2)

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3
Q

What are enteric viruses?

A

E.g polio, rotaviruses, reoviruses and some adenoviruses - cause gastric infections
(Slide 2)

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4
Q

Where do enteric viruses replicate?

A

In the gut
(Slide 2)

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5
Q

How are enteric viruses acquired?

A

By ingestion of faecal-contaminated material
(Slide 2)

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6
Q

What are arboviruses?

A

e.g - flaviruses, bunyavirus and some rhabdoviruses - they infect insects that ingest vertebrate blood and then replicate in the tissue of the insect and become transmitted to the vertebrate host
(Slide 2)

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7
Q

What are respiratory viruses?

A

E.g influenza, rhinoviruses, adenoviruses, usually acquired by inhalation of droplets
(Slide 2)

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8
Q

What are hepatitis viruses?

A

All viruses that cause liver disease
(Slide 2)

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9
Q

Where do respiratory viruses replicate?

A

Usually in the respiratory tract
(Slide 2)

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10
Q

What type of viruses are easiest to grow?

A

Bacterial viruses
(Slide 3)

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11
Q

How can animal viruses (and some plant viruses) be cultivated?

A

In tissue or cell cultures
(Slide 3)

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12
Q

Why are plant viruses usually the hardest to grow?

A

As they often require the growth of a whole plant in order to be studied
(Slide 3)

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13
Q

What does a titer refer to?

A

The number of infectious units per volume of fluid
(Slide 3)

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14
Q

What is a plaque assay?

A

It is analogous to the bacterial colony and is one way to measure virus infectivity
(Slide 3)

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15
Q

What does each plaque result from?

A

Infection by a single virus particle
(Slide 3)

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16
Q

What are viruses without membranes called?

A

Naked viruses
(Slide 7)

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17
Q

What does a virion consist of?

A

A nucleic acid packaged into a protein coat (known as a capsid)
(Slide 8)

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18
Q

What is a nucleic acid and protein packaged into a virus particle called?

A

The nucleocapsid
(Slide 8)

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19
Q

What does lysozyme do?

A

Makes a hole in the cell wall and lyses bacteria
(Slide 9)

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20
Q

What are neuraminidases?

A

Enzymes that cleave glycosidic bonds which allows liberation of viruses from the cell
(Slide 9)

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21
Q

How are viruses classified today and what is this classification called?

A

Baltimore classification - viruses are classified based on how they replicate
(Slide 11)

22
Q

What are the 7 classes of viruses in the Baltimore classification?

A

I - dsDNA
II - ssDNA (+) sense
III - dsRNA
IV - ssRNA (+) sense RNA
V - ssRNA (-) sense
VI - ssRNA (+) sense with dsDNA intermediate
VII - dsDNA with RNA intermediate
To help remember - 3 with DNA - 4 with RNA + one with dsDNA intermediate
(Slide 11)

23
Q

What is the equivalent of the “lag” phase in a one step growth experiment involving viruses?

A

Latent period
(Slide 12)

24
Q

What comes after the latent period in a one step growth experiment?

A

Assembly + Release
(Slide 12)

25
Q

What are the 3 main stages of virial replication?

A

Initiation
Replication
Release
(Slide 13)

26
Q

What are the 4 substages in the initiation stage of virial replication?

A

Recognition
Attachment
Penetration
Uncoating
(Slide 13)

27
Q

What are the 4 sub-stages of replication stage of virial replication?

A

Transcription
Protein synthesis
Genome replication
Assembly
(Slide 13)

28
Q

What are the 3 different mechanisms of release in virial replication?

A

Lysis and release (naked viruses)
Exocytosis
Budding and release (for non-naked viruses only)
(Slides 13 and 23)

29
Q

What are the early and late phases of virial replication?

A

Early phase covers initiation stage of virial replication
Late phase covers replication and release stages
(Slide 13)

30
Q

What are the 3 possible things which a virial attachment protein could be?

A

The capsid, a protein which extends from the capsid, or glycoproteins of enveloped viruses
(Slide 14)

31
Q

What are the steps of pore-mediated penetration (also known as viropexis)?

A
  1. Attachment
  2. Pore mediated penetration
  3. Viral genome gets inserted into plasmid
    (Slide 16)
32
Q

What kind of viruses can undergo pore-mediated penetration (viropexis) ?

A

Naked viruses
(Slide 16)

33
Q

What occurs in virial endocytosis?

A

The virus attaches to the host cell and can then enter it via endocytosis
(Slide 17)

34
Q

What 2 virus types can undergo virial endocytosis?

A

Naked and enveloped
(Slide 17)

35
Q

What occurs in membrane fusion involving viruses?

A

The virus fuses membrane with the cell to insert its genome
(Slide 17)

36
Q

What is the difference between DNA and RNA dependent DNA polyremase?

A

DNA dependent - copies DNA and makes DNA
RNA dependent - copies RNA and makes DNA (reverse transcriptase)
- always results in DNA being formed
(Slide 18)

37
Q

Where does transcription of the genes of DNA viruses occur?

A

In the nucleus (excluding poxviruses)
(Slide 19)

38
Q

Why are DNA virus’s virial regulatory regions similar to that of the hosts?

A

By mimicking host regulatory sequences, DNA viruses can hijack the host cell’s transcriptional machinery to regulate the expression of viral genes and facilitate viral replication
(Slide 19)

39
Q

What is the difference between DNA and RNA dependent RNA polyremase?

A

RNA dependent - copies RNA and makes RNA (RNA viral replication)
DNA dependent - copies DNA and makes RNA (transcription)
- always results in RNA being formed
(Slide 18)

40
Q

What is a smaller virus more dependant on?

A

It’s host
(Slide 19)

41
Q

What do many DNA viruses promote?

A

Cell growth
(Slide 19)

42
Q

What kind of mRNA is transcribed first in DNA viruses?

A

mRNA for non-structural proteins -(early phase proteins)

43
Q

What initiates transcription of late phase genes in DNA virial replication?

A

Genome replication
(Slide 19)

44
Q

Where is DNA replication initiated?

A

The origin (Replication origins)
(Slide 19)

45
Q

What must be virus encoded (made by the virus) for use in RNA virus replication?

A

Polymerase enzymes
(Slide 20)

46
Q

Where does replication of RNA viruses occur?

A

In the cytoplasm (excluding influenza)
(Slide 20)

47
Q

What are RNA viruses more prone to?

A

Mutation
(Slide 20)

48
Q

What kind of mRNA are eukaryotic ribosomes unable to translate?

A

Polycistronic mRNA
(Slide 21)

49
Q

What is polycistronic mRNA?

A

mRNA which contains coding sequences of multiple proteins
(Slide 21)

50
Q

What are the 2 main morphologies of viruses?

A

Helical and icosahedral viruses
(Slide 22)

51
Q

What occurs in virial exocytosis?

A

The new virions are transported to the cell membrane and either their envelopes, or just their membranes fuse with the host membrane to allow release from the cell
(Slide 23)

BM211: Introduction to Microbiology (21 decks)

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