1. VIRUSES

2. Characteristics of Living Things
Organized – cells, tissues, organs, etc
Reproduce
Grow and develop
Adjust to their environment
Adapt and evolve
Which of these characteristics
do viruses have?

3. Viruses Characteristic Yes No Organized X Reproduce* Grow and Develop
Adjust to environment
Adapt and evolve
Viruses are NON-LIVING organisms
NOT named with binomial nomenclature or classified with other organisms
Named for the disease which they cause or the tissue they infect
*Viruses cannot reproduce by themselves, they must have help from a living cell!

4. Structure Capsid: outer protein coat Core: DNA or RNA
DNA virus=Provirus
RNA virus = Retrovirus
Envelope: membrane that surrounds the capsid of some viruses

5. Replication Attachment Entry Lysogenic/Lytic Cycle
Viruses are specific, they can only attach to specific cells of a specific species of organism
Entry
Viral genetic info is injected into host cell and is inserted into host cell’s DNA
Lysogenic/Lytic Cycle
Host cell’s resources are used to make viral DNA and eventually new viruses

6. Viral Replication Lysogenic Cycle Lytic Cycle
Viral DNA does not take over cell right away
Cell functions and replicates normally
Since viral DNA is incorporated with host DNA each daughter cell contains viral DNA
Once virus is activated, it enters lytic cycle
Lytic Cycle
Viral genes expressed as cell transcribes and translates its own DNA
Viral DNA takes over and new viruses are made, using all available resources
Newly made viruses burst from cell, killing host cell
New viruses can infect other cells

8. Interesting Viruses Bacteriophage Retroviruses (HIV)
Virus that infects bacteria
Can speed up evolution of
by transporting genes
Retroviruses (HIV)
RNA virus
Virus must make DNA from RNA before it can take over cell
The enzyme reverse transcriptase makes DNA from RNA (opposite of what we learned!)

9. Viruses In History HIV – Human Immunodeficiency Virus Retrovirus
Attacks white blood cells so you can’t fight off other infections

10. Viruses In History Smallpox- small raised blisters all over body
Biological Weapon - French and Indian War
Blankets infected with small pox caused an epidemic that decimated Native American population
Considered eradicated in most parts of the world

11. Viruses In History HPV- Human papillomavirus
Affects skin and mucus membranes
Recently shown to cause cervical cancer
Vaccine available

12. Can Viruses Be Helpful? Increase genetic variation
A virus inserts its DNA into the cells DNA causing a “mutation” in the cell’s DNA
Genetic recombination technology
Can be used as vectors
Immunization
Killed or weakened viruses can be injected to create antibodies so that you are protected from future exposure.