1. Viruses
Biology 2
Mr. Beyer

2. Bacteriophage

3. What is a Virus? Non-cellular Particle (not made of cells)
Genetic Material will be one or the other
DNA
RNA (retrovirus) makes DNA from RNA instead of process where DNA is made from RNA
Protein Coat (covering around nucleic acid)
No independent cellular reproduction
No cellular independent cellular metabolic capabilities

4. Two Types of Viral Infections
Lytic Cycle
The virus kills the host cell immediately creating symptoms of the disease…fever, pain, swelling, sores….
Lysogenic Cycle
Virus enters the host cell and remains dormant
Formation of a provirus (the virus DNA has attached itself to the host DNA)

5. Lytic Cycle
Attachment (Adsorption)-Attaches to the host cell receptor sites
Entry-The virus injects is Nucleic Acid (DNA or RNA) into the host cell
Provirus Formation-Virus nucleic acid attaches to host cell nucleic acid (formation of provirus)
Replication-Host cell replicates its DNA with virus DNA attached. The host cell unwittingly makes virus parts.
Assembly- Virus parts are assembled inside the host cell.
Lysis-Viruses fill the host cell, release an enzyme that breaks open the cell membrane and releases the viruses, killing the host cell…….symptoms appear in organism

6. Lysogenic Cycle
Attachment (Adsorption)-Attaches to the host cell receptor sites
Entry-The virus injects is Nucleic Acid (DNA or RNA) into the host cell
Provirus Formation-Virus nucleic acid attaches to host cell nucleic acid (formation of provirus)
Cell Division-Cells divide, replicating viral DNA with host cell DNA.
Replication-Host cell replicates its DNA with virus DNA attached. The host cell unwittingly replicating viral nucleic acid.
DORMANCY…… few or no symptoms or the disease….. virus remains dormant for a period of time…..eventually the virus will complete its life cycle and continue to the lytic cycle, killing the host cell

7. Lytic Cycle

8. Virulence A virus’s ability to cause disease
Common cold (low virulence)
HIV (high virulence)