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Viruses are small infectious particles consisting of:
- -Nucleic acid
- -A protein coat
- -(in some) a membranous envelope
Viral genomes may consist of
Double or single stranded DNA or RNA
A capsid is
- the protein shell that encloses the viral genome
- -it's built of subunits called capsomeres
Viral envelopes are derived from the host cell's membrane and surround
the capsids of viruses
What are the two reproduction mechanisms of phages?
The lytic and lysogenic cycles
The lytic cycle causes what?
- Death of the host cell.
- A phage that only undergoes the lytic cycle is called a virulent phage
5 stages of the lytic cycle?
- Entry of phage DNA, degredation of host DNA
- Synthesis of viral genomes and proteins
The lysogenic cycle replicates the phage and...
does not destroy the cell
when viral DNA is incorporated into the host's chromosome during the lysogenic cycle
Describe the process of the Lysogenic cycle
- Phage injects the DNA into the cell
- The bacterium reproduces, copying the prophage
- Cell divison produces more - daughter cells with prophase
Temperate phages are...?
Phages that use both the lytic and lysogenic cycles
Two key variables used to classify viruses that infect animals?
- 1) DNA or RNA?
- 2) Single or double stranded
Two possible candidates for viral genome sources?
- Plasmids - circular DNA in bacteria and yests
- Transposons - small mobile DNA segments
Viroids are circular RNA molecules that infect...
plants, and disrupt their growth
Prions are slow-acting, virtually indestructable infectious proteins that...
- cause brain diseases in mammals
- *Prions propagate by converting normal proteins to prions