What are viruses? Flashcards

1
Q

Importance of Koch and Pasteur in virology

A

Developed porcelain-based filter

Contaminated liquids that passed through = no longer infectious

Viruses could pass through - turning point for virology

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2
Q

Importance of Dmitri Ivanovski in virology

A

Investigates the tobacco mosaic virus

Infected leaves had patched appearance - light sections = dead

Mashed infected leaves into extract and ran through filter

Still caused disease -> transmissable entity could not be filtered away

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3
Q

Importance of Martinus Beijerinck in virology

A

Investigated tobacco mosaic virus

Agent causing disease could only multiply on living plants

So replicating agent = not a toxin

Thought it was a poisonous living fluid

Came up with name virus

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4
Q

Importance of Loeffler and Frosch in virology

A

Same filter observation

But with human virus

Foot and mouth virus

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5
Q

Importance of Walter Reed in virology

A

Described the yellow fever virus

Was the first human virus

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6
Q

What are the 3 basic characteristics of viruses?

A

Small - can be filtered

Dependent on host - different from all other organisms

Transmissible - key to viral survival

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7
Q

What is the importance of transmission in viruses?

A

Key to viral survival

Everything about virus biology is focused on securing transmission to a new host

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8
Q

What is another way of describing viruses?

A

By what they don’t do compared to other biological entities

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9
Q

What do viruses not do compared to other biological entities?

A

Grow

Respond to stimuli

Consume energy

Undertake homeostasis - same environment inside as outside the virus

Reproduce

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10
Q

What happens to viruses without a host?

A

Becomes inert

No biological characteristics

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11
Q

Average size of viruses?

A

20 - 300 nm

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12
Q

What are the two key components of viruses needed for them to transmit from one host to another?

A

Genome

Container for the genome

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13
Q

What is a viral genome?

A

Encodes information to direct the host cell to generate new viruses

Can be made of DNA or RNA

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14
Q

What is the container of a viral genome?

A

Necessary to get the genome from one host to another

Called capsid - protein shell that protects the genome

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15
Q

What is a capsid?

A

Container for viral genome

Made of protein

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16
Q

What is a virion?

A

Complete infectious virus particle

17
Q

Structure of a virus

A

Genome -> Capsid -> Matrix/ Tegument -> Envelope

18
Q

What is the matrix/ tegument?

A

Layer between the capsid and the envelope

19
Q

What is a nucleocapsid?

A

Name given to the capsid of a virus with the enclosed nucleic acid

20
Q

Do all viruses contain matrix/tegument?

A

No

21
Q

Do all viruses contain an envelope?

A

No

Most human viruses contain one

Plant viruses don’t

22
Q

What is a viral envelope?

A

Phospholipid bilayer

Made by host cell

Encloses nucleocapsid

Contains viral glycoproteins

Is always spherical, even if the capsid inside is helical or icosahedral

23
Q

What are the 2 possible shapes of viruses?

A

Icosahedral

Helical

24
Q

Structure of icosahedral viruses

A

Platonic solids - spheroid structure made of 20 triangular phases

Symmetrical

Efficient way of enclosing space

25
Q

Viruses with icosahedral structures

A

Adenovirus

Polio

Herpes

26
Q

Structure of helical viruses

A

Genomes are helical and curl

Assembly of structure follows coils of DNA

Thin, long, circular structure

27
Q

Which viruses have helical strucures?

A

Single stranded RNA viruses

DNA viruses

28
Q

Why are virus structures simple?

A

Building a structure with few parts increases the genetic economy

Have to code for less proteins

Reduces the genome for the virus, which is beneficial

29
Q

What are the 5 theories describing the origin of viruses?

A

Progressive

Regressive

Virus first

None of the above

All of the above

30
Q

What does the progressive hypothesis of origin of viruses describe?

A

Viruses evolved from bits of DNA or RNA

Like plasmids and transposons

Plasmids - molecules of DNA that can move between cells

Transposons - molecules of DNA that can replicate and move to different positions within a cell

Retroposons - Transposons that move to a new place via RNA intermediate

Viruses are replicating nucleic acids - independent transposions or retroposons

31
Q

What does the regressive hypothesis of origin of viruses describe?

A

Small cells used to parasitise larger cells

Lack of genetic economy

Abandoned the genes required to survive outside the cell

Complex progenitor cell shed functions and became more dependent

32
Q

What does the virus first hypothesis of origin of viruses describe?

A

Viruses prefate cells

Self-replicating, catalytic molecules that led to life

33
Q

Origin of HIV

A

Can be traced via phylogenetic tree

Zoonotic infection - simian

HIV is a primate virus

Came from transfer of monkeys -> human