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VIRUSES
By: Kurt DawiecClass: 717Date: January 28th, 2010
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What is a virus? A VIRUS: Can reproduce Is nonliving Does not have organelles Does not grow Does not take in food or make waste Is a piece of nucleic acid covered with
a protein (this protein is called a capsid)
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What is a virus? A VIRUS: Needs the help of living things. A virus is a parasite. PARASITE - an organism that survives
by existing on or in a host organism
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How big is a virus?
http://learn.genetics.utah.edu/content/begin/cells/scale/
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How does a virus reproduce?
http://www.tvdsb.on.ca/westmin/science/sbi3a1/Bacvirus/Virusrep.htm
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A bacteriophage virus:
Bacteriophage – virus that infects bacteria
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How does a virus reproduce? 5 Steps: 1 – Virus attaches
to a cell
2 – Injects genetic material into the cell
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How does a virus reproduce?
3 – Genetic material directs the cell to make more virus parts
• 4 – The parts form new viruses
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How does a virus reproduce?
5 – The cell membrane bursts, releasing new viruses
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How does a virus reproduce?
http://www.tvdsb.on.ca/westmin/science/sbi3a1/Bacvirus/Virusrep.htm
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How does a virus reproduce?
A virus can be inside a living thing and remain inactive
Ex: cold sore
The cell is not always destroyed when viruses leave the cell.
Ex: HIV
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How do we classify viruses?
Viruses are NOT in the five kingdom system
Scientists used to classify viruses based on the host (Ex: plant virus, animal virus)
Today viruses are classified by their shape and structure
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How do we classify viruses?
3 characteristics used to classify viruses:
1 – Structure of capsid 2 – Type of nucleic acid (DNA or RNA?) 3 – The way the virus reproduces
Usually the common name of a virus is based on the disease that it causes
Example: Swine flu virus, Rabies virus
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Head
Tail
Capsid
Tail Fibers
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