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IMIN 200 > Magor- Lecture 1: Virus > Flashcards

Magor- Lecture 1: Virus Flashcards

1
Q

What is the size of a virus relative to a bacterium?

A

Viruses are small (30-90 nm)
Bacterium ~ 1 micron

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2
Q

Is a virus a living thing? Why or why not?

A

No. Viruses lack the essential of life

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3
Q

Give two facts about a virus

A
  • Protecting ‘contents’ from external environment
  • evolve by natural selection
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4
Q

Are viruses able to take up energy and make use of it?

A

No

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5
Q

Are viruses able to transport- of cell; into cell; within cell?

A

No

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6
Q

Do viruses reproduce themselves?

A

No

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7
Q

What makes viruses obligate parasites?

A

They must have a host cell to reproduce

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8
Q

Viruses have highest mutation rates in ________ genomes

A

smallest

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9
Q

Virus is a latin word meaning ______

A

poison

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10
Q

3 things a virus needs

A
  1. To be able to enter a host cell
  2. Have the host cell replicate the viral genetic material
  3. Have the host cell transcribe and translate the viral genes
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11
Q

What happens once all the virus components are made?

A

Once all the virus components are made the infectious viral particle (virion) can be assembled.

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12
Q

In 1901, they identified the first human virus ______________

A

yellow fever virus

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13
Q

He is a Cuban scientist who linked yellow fever to mosquito transmission in 1881?

A

Carlos J. Findlay

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14
Q

He went to Cuba to test the theory of mosquito transmission

A

Dr. Jesse Lazear

Lazear never directly admitted to experimenting on himself but Reed reviewed Lazear’s sketchy notations that he evidently found entries strongly suggesting Lazear’s case was not accidental.

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15
Q

He used army volunteers to prove mosquitoes transmitted yellow fever virus.

A

Dr. Walter Reed

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16
Q

She is a US army nurse who agreed to be infected twice but didn’t survive the 2nd infection, which means the virus probably shuts down some immune memory

A

Carla Maass

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17
Q

What is the yellow fever case fatality rate

A

20%

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18
Q

This disease is known since the 1700s-caused by ‘miasma’ although convincing descriptions date back to Hippocrates (2400 years ago)

A

Influenza

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19
Q

What year was the first identification of human influenza?

A

1933

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20
Q

Why are ferrets good animal model for influenza research?

A

Because they have similar symptoms that humans have (ie. sneezing)

21
Q

Egg allantoic fluid

A
  • this is what we use now to recover viruses and grow viruses used for vaccines
  • the eggs have been fertilized and incubate for about 10 days. The chick is starting to grow in that egg in 10 days. You can infect that membrane and fluid around the egg
22
Q

River’s Postulates (modified Koch’s postulates) - how you workout what caused the disease.

What are the 6 postulates?

A
  1. Isolation of virus from diseased hosts (harder than it seems because lots of viruses have self-limiting infection)
  2. Cultivation of virus in host cells
  3. Proof of filterability (confirms small size; tells you that the causative agent is not a bacteria, it is possibly a virus)
  4. Production of a comparable disease when used to infect experimental animals (host animal or related)
  5. Re-isolation of the same virus form the infected host
  6. Detection of a specific immune response to the virus
23
Q

Case study: a patient is referred to you from airport heat screening.

What viruses can be detected by the fever they cause?

A

Coronavirus

24
Q

Why might a viral infection go undetected by airport heat screening scanners?

A

It could be the virus caused the before before or after they’re still infected.

25
Q

All viruses follow a general strategy: (3)

A
  • They package their genomes inside a particle that mediates transmission from host to host
  • A virus genome contains the information for an infectious cycle within a susceptible permissive cell
  • All viruses are able to establish themselves in a host population so that their survival is ensured
26
Q

Do viruses intent to kill their hosts?

A

No, viruses don’t intend to kill their hosts

27
Q

Capsid (protein sheath)

A

protects the nucleic acid

viruses are covered with this

28
Q

Their experiment in 1952 proved that DNA is the genetic material

A

Hershey and Chase

29
Q

Both of these viruses have a capsid but they also have a membrane around their surface

A

Influenza and Coronavirus

30
Q

This protects the genetic material of the virus. It is resistant to all kinds of environmental factors

A

Capsid

31
Q

Viruses that don’t have a membrane such as the Tobacco mosaic virus (TMV) are

A

Very resistant to anything - proteases, heat or temperature extremes

uses as few proteins as possible

32
Q

Enveloped viruses such as HIV, Coronavirus, Influenza are

A

much more susceptible to the environment

they have that membrane and that membrane can’t dry out. If the membrane dries out, that virus is no longer viable and able to infect cells.

33
Q

Arrangement of nucleic acid and protein coat in tobacco mosaic virus

A
  • The RNA assumes a helical configuration surrounded by the protein capsid.
  • The information for assembly is contained within the protein structure itself (self-assembly)
34
Q

Self-assembly

A
  • A process that a lot of viruses do

If you put the structural subunits (protein) and virus RNA in a test tube together, it automatically assembles.

35
Q

How does the virus ‘know’ how to assemble?

A

All of the things that are necessary for the correct assembly of this protein host and the RNA strand that it coats are inherent in the structure of that protein.

36
Q

Packaging and structure of poliovirus proteins in the capsid

A
  • uses 60 copies of each 4 proteins to generate the icosahedral shape
  • assembly uses as few proteins as possible-easier synthesis
  • capsid only for norovirus-persistence in the environment
37
Q

How does poliovirus leave the cell?

A

Poliovirus leaves the cell by rupturing. They’re gonna synthesize 50,000 copies of itself in 24 hours

38
Q

Simplified viral life cycle steps (5)

A
  1. Attachment -viruses use a variety of receptors
  2. Penetration -crossing the membrane
  3. Utilization -host cell proteins/enzymes needed for replication, transcription & translation
  4. Biosynthesis -synthesis of proteins
  5. Assembly -progeny particles are produced
39
Q

Life cycle of an enveloped RNA virus (Measles, CoV, Influenza)

A
  1. The viral envelope membrane fuses with the host cell membrane to allow entry.
  2. RNA is transcribed & replicated using viral enzymes.
  3. Virus can leave cell by budding off, taking some host cell membrane with it.
40
Q

What is the source of the enveloped for enveloped viruses?

A

The host cell

41
Q

How does the membrane help the virus hide from our immune system?

a. it is of host origin
b. contains viral proteins
c. contains host proteins
d. a & c are correct

A

D

42
Q

Viruses replicate via _________ growth

A

exponential

Viruses synthesize progeny de novo and release a large number at once
eg. Poliovirus 1-50,000 particles in 24 hours

43
Q

How is the viral titre determined or how much virus is present?

A

Using a plaque assay

  1. A dilution is mixed with bacteria and melted agar
  2. Pour onto agar plate
  3. Phage plaques make ‘holes in lawn’
44
Q

What is the virus titre? Concentration reported as:

a. bacteria/mL
b. viruses/mL
c. plaque forming units/mL
d. particles/mL

A

C

45
Q

Virus classification is based on: (3)

A
  • the nature of the genetic material
  • symmetry of the capsid
  • presence of an envelope, dimensions
46
Q

Virus genetic material can be:

A

DNA or RNA (single stranded or double stranded)

47
Q

Examples of RNA viruses

A

Norovirus
Polio
HIV
CoV
Influenza
Measles

48
Q

Examples of DNA viruses

A

Herpes
Pox

IMIN 200 (20 decks)

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