Micro Ch 6,11
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What is a virus?
- An obligatory intracellular parasite
- all have a protein coat
- target host cell receptors
What is the basic structure determining shape?
- the capsid
- encoded for in the viral genome
- it's composed of repeated protein subunits, minimizing the number of genes requires.
- two main capsid forms: symmetrical and asymmetrical
What is the virus protein coat?
What determines host range?
- available receptors
- cellular factors
- types of hosts a virus can infect
Symmetrical vs Asymmetrical Viruses
- symmetrical: filamentous or icosohedral
- asymmetrical: T4 bacteriophages, poxviruses
What occurs in the lytic cycle?
- bacteriphage replicates quickly, killing the host
- the host cell explodes, releasing the bacteria
What happens in the lysogenic cycle?
- bacteriphage is quiescent
- integrates into cell chromosome as PROPHAGE
- can reactivate to become lytic
What is tranduction?
the mechanism by which DNA moves from one bacterium to another (when a virus takes some of the host DNA with it)
What are the viral genome types?
- Single/double stranded
What are the three main viral genomes?
- DNA viruses
- RNA viruses
What are the steps of the animal virus life cycle? (in order)
What is the DNA life cycle?
- virus enters cell and travels to nucleoid before uncoating
- Uses host polymerase to create RNA template then replicate
What is the RNA life cycle?
- RNA genome inserted into host cell
- viral genome replicated using RNA dependant RNA polymerase
- NEVER CONVERTS TO DNA
- lyses host
What is the retrovirus life cyle?
- Binds to host then uncoats envelope, sending the capsid into host.
- Uses ITS OWN reverse transcriptase, which creates a DNA copy of the original RNA genome.
- DNA copy is inserted into host genome.
- buds off host, creating envelope
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