Download Viruses Handout

Viruses
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Basically lifeless until they enter a host cell.
Use cell organelles to reproduce.
Typically a protein capsule with DNA or RNA inside.
Because of this, viruses are NOT considered to be a living thing.
Viruses usually infect a specific host species.
 Often can only infect certain cells of host.
The Lytic Cycle:
• Replication cycle of virus:
1. Attachment
– Virus or its DNA/RNA enters host
2. Synthesis
– Viral DNA/RNA instructs host to
manufacture viruses
3. Assembly
– New viruses are assembled
4. Release
– New viruses are released as cell bursts
Mutation
• Mutation of viral DNA can lead to new versions of a virus.
• Like evolution.
• Can also lead to cross-species infection.
Vaccination
• Stimulate (train)
your immune
system.
• Introduce a
dead/weakened
form of virus.
• Immune cells learn
to recognize and
produce response
(i.e. antibodies).
• This allows a faster
response when
infected later.
The Lysogenic Cycle:
• Same as previous, but cells are not destroyed.
• They continue to reproduce normally as they make
viruses.