VIRUSES

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?

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!

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

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

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

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!)

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

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

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

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.