Download Plate 32 - Viral Replication

Plate 32
Viral Replication
What do computer viruses do?
• Infect your computer
• Take it over (perform some task)
• Spread to other computers
Hosts
• There are viruses that infect every kind of
organism: animals, plants, fungi, bacteria,
protists, etc.
• Viruses that infect bacteria (bacteriophages)
have been studied the most
Viral Replication
• In general, viruses:
– Attach to the host cell in the union phase
– Insert their viral genetic material in the
penetration phase
– Create mRNA in the transcription phase
– Make proteins in the synthesis phase
– Build new viruses in the assembly phase
– Break out of the host cell in the release phase
1. Union Phase (Adsorption)
• Capsid proteins only bind with specific
receptors on the host cell’s surface
– This gives viruses their host range (which type of
organism it may infect)
2. Penetration Phase
• The virus inserts its genetic information (DNA
or RNA) into the host cell through the cell
membrane
• Remainder of the virus is left outside the cell
• http://www.youtube.com/watch?v=F5WEDcN
cJjY
3. Transcription Phase
• Viral DNA is used as a template to create
messenger RNA (mRNA)
4. Synthesis Phase
• mRNA moves to the ribosomes within the host
cell
• Just like a blueprint, the mRNA begins coding
for specific proteins
5. Assembly Phase
• Components of viruses are built from the
proteins created in the synthesis phase
• Viral DNA is made up of the same nucleotides
used to make the bacterial DNA
• Capsids begin to be assembled around the
viral DNA
6. Release Phase
• After several hundred
viruses are assembled, an
enzyme (lysozyme) is made
to rupture the host cell wall
• The host cell dies and
hundreds of new viruses are
released to infect new hosts
Lytic vs. Lysogenic