1. Virus
A pathogen that consists of a Nucleic Acid – (DNA or RNA) wrapped in a Protein Coat- (Capsid).
Classification:
Classified by the host
Bacteriophage infects bacteria

2. Reproduction Occurs only in a host cell. 2 types:
Lytic Cycle: Virus enters cell, makes copies of itself, and kills the cell.
Lysogenic Cycle: hides in the DNA and replicates with the host cell until conditions allow it to enter the lytic cycle.

3. Lytic Cycle Steps: The virus attaches to a cell
The virus inserts their genetic info into the cell
The virus breaks down the cell’s genetic information and starts to produce virus parts
The new virus parts are assembled
The new viruses are cause the cell to lyse (burst)

4. Lytic Cycle

5. Lysogenic Cycle Steps
Virus integrates its DNA into the DNA of the host cell
The viral genetic information replicates along with the host cell’s DNA indefinitely.
When conditions are favorable, the virus will switch to the Lytic cycle and start killing the host cell.

6. Lysogenic Cycle

7. Retroviruses Contain RNA as their genetic information.
Named because they work backwards
Normal: DNA – RNA – tRNA – Protein
Retrovirus: RNA – DNA – RNA – tRNA – Protein
(virus) (host cell)
Example: HIV

8. Vaccine
Injecting someone with a weakened form of a virus