4 - Viral properties Flashcards

1
Q

What is meant by obligate?

A

cannot complete its lifestyle (replicate) without being inside a host cell
(uses the host cell machinery)

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2
Q

What are the characteristics of the non-enveloped virus morphology?

A

have a protein capsid and and symmetrical

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3
Q

What are the characteristics of the enveloped virus morphology?

A
  • have proteins around their genome
  • have a lipid envelope around them which is derived from the membrane of the host cell
  • are PLEOMORPHIC - have lots of different shape
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4
Q

Which morphology does the Herpes virus have?

A

it is a combination of capsid and envelope

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5
Q

What are the features of RNA viruses and retroviruses?

A
  • use own polymerises to replicate
  • very error prone and lack proofreading capacity
  • high mutation rate
  • RNA virus genome is limited in size die the instability of its DNA
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6
Q

What are the features of DNA viruses?

A
  • larger (since DNA is more stable)
  • there is space for accessory genes
  • genome can be one long strand or can be segmented e.g. influenza
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7
Q

Viral Replication:
What is the name of the protein on the surface of the virus that binds to the receptor on the host cell in the first stage?

A

viral attachment protein

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8
Q

Viral Replication:

What are the 2 ways that viruses enter the host cells?

A
  • fusing with the host cell membrane and injecting the DNA/RNA genome into the cytoplasm
  • enter via a series of vesicles such as endosomes
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9
Q

Give the generic virus replication cycle

A
  • there is an inert virus on the outside
  • its viral attachment protein binds to a receptor on the host cell surface (this docks down the virus onto the cell surface)
  • virus enter the cell
  • the viral genome is made into messenger RNA
  • host ribosomes are used to translate the mRNA and make proteins
  • at the same time, the genome is being replicated (either using viral or the host cells polymerases)
  • the copies of the gnome and the viral proteins assemble to form new viral particles, which than leave the cell
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10
Q

Describe the replication cycle of influenza

A
  • spike proteins are used to attach to the surface of the host cell
  • it is engulfed and taken into an endosome
  • it then fuses and releases its genome
  • the genome enters the nucleus where it replicated and directs the synthesis of proteins
  • they come other to form new virus particles
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11
Q

Describe the replication cycle of Ebola virus

A
  • starts off as a worm like virus outside of the cell
  • attaches to the cell receptor and is macropinocytosis
  • in the early endosome it undergoes various cleavages, so it can interact with different receptors
  • the genome is released and is copied into new genomes and into mRNA, to produce proteins
  • proteins and genomes come assemble and bud out to form new virus particles
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12
Q

Describe the single step growth kinetics of a virus?

A
  • the amount of virus at the start is know
  • eclipse phase - no virus because all of it has gone into cells
  • logarithmic increase - the virus makes new copies and exits the cells
  • cell death - it tails off because cells start dying
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