1. Viruses

2. Key Viral Parts Head/Capsid: Protects DNA or RNA
Constructed of protein
Genome/DNA: Instructions for replication (composed of nucleic acids)
Tail Fibers: Attach to host cell; made of protein

3. Characteristics of Living Things
Made of cells
Respond to stimuli
Adapt to environment
Obtain & use energy
Grow & develop
Reproduce

4. Viral Characteristics
Require other cells (from host) in order to survive
Do not need food to survive
Not cellular
BUT, they do use DNA or RNA as a replicating molecule… So… living or not?

5. Definitions
Virus: Non-cellular; contain genetic information & protein; invade living cells to reproduce
Viruses are VERY specific to their host… They will only infect specific organisms (ex. plant viruses won’t affect humans)

6. Lytic Cycle Diagram Phage DNA Bacterial chromosome New phages
Phage attaches to host cell and injects DNA
Phage DNA forms circle
New phage DNA and proteins are synthesized
Bacterium lyses (bursts), releasing new viruses

8. Lysogenic Cycle
d. Prophage e. Replicated bacterial chromosome with prophage
5. Phage DNA incorporates into bacterial chromosome 6. Bacterium reproduces, passing prophage to daughter cells 7. Colony of infected bacteria forms 8. Prophage leaves bacterial chromosome & initiates lytic cycle