4 - Viral properties Flashcards Preview

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Flashcards in 4 - Viral properties Deck (12):

What is meant by obligate?

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


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

have a protein capsid and and symmetrical


What are the characteristics of the enveloped virus morphology?

- 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


Which morphology does the Herpes virus have?

it is a combination of capsid and envelope


What are the features of RNA viruses and retroviruses?

- 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


What are the features of DNA viruses?

- 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


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?

viral attachment protein


Viral Replication:
What are the 2 ways that viruses enter the host cells?

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


Give the generic virus replication cycle

- 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


Describe the replication cycle of influenza

- 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


Describe the replication cycle of Ebola virus

- 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


Describe the single step growth kinetics of a virus?

- 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