1. Plate 32
Viral Replication

2. What do computer viruses do?
Infect your computer
Take it over (perform some task)
Spread to other computers

3. 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

4. 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

5. 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)

6. 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

7. 3. Transcription Phase
Viral DNA is used as a template to create messenger RNA (mRNA)

8. 4. Synthesis Phase mRNA moves to the ribosomes within the host cell
Just like a blueprint, the mRNA begins coding for specific proteins

9. 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

10. 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

11. Lytic vs. Lysogenic