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=F5WEDcNcJjY

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