What is a virus? small infectious agent that can replicate only inside the cells of other...
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![Page 1: What is a virus? small infectious agent that can replicate only inside the cells of other organisms. Viruses are too small to be seen directly with.](https://reader033.fdocuments.net/reader033/viewer/2022051401/5697bfc51a28abf838ca652f/html5/thumbnails/1.jpg)
VIRUSES…IT’S LATIN FOR POISON
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What is a virus?
small infectious agent that can replicate only inside the cells of other organisms. Viruses are too small to be seen directly with a light microscope.
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What can all viruses do?
REPRODUCE!!! They can not reproduce on their own Viruses require a HOST cell to infect
and reproduceHOST= another organisms cell
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What are viruses named after? Named after the disease they cause
Ex: Influenza virus causes the influenza or
the flu Poliomyelitis causes polio Chicken pox virus causes chicken pox
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What is a virus that infects a bacterium called? Called a
bacteriophage
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Viral Structure
2 Major Parts Inner Coregenetic info. Viruses have either RNA or DNA as genetic material Outer Core capsid head
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Viral Replication Cycle
2 Types of Cycles LYSOGENIC and LYTIC Lytic Replication: virus injects genetic
info inside host cell, replicates, and lyses (burst and kills) the host cell as viruses leave the cell particle . ATTACH INJECT SYNTHESIZE LYSE
Lysogenic Replication: viral genetic info becomes incorporated with host cell. Viral genetic info is now replicated every time host cell makes new cell
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LYTIC CYCLE
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LYSOGENIC CYCLE
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Viruses Website
http://leavingbio.net/VIRUSES%20WEBPAGE.htm
http://www.courses.fas.harvard.edu/~biotext/animations/lysogeny.html
http://www.courses.fas.harvard.edu/~biotext/animations/lyticcycle.html
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PROVIRUS
Viruses that use the lysogenic cycle They incorporate themselves into the
host DNA Can replicate without lyses of the cell Retroviruses are proviruses HIV is an example a provirus
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Why are retroviruses so different
Takes its genetic information (RNA) and tricks the host manufacture its viral DNA.
Host then replicates its own as well as the retrovirus DNA
Oncogenic viruses will convert normal cells into tumor cells (Oncoviruses, Lentiviruses)
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First Virus Identified
Tobacco mosaic virus Infected tobacco and other plants Discovered in 1892 by Dmirti
Iwanowsk
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Where do scientists suggest that viruses come from?
No clear answer Some suggest that they came from
parasites, others say that they were bits of genetic info that separated from a cell
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Are all viruses bad?
No!!! Viruses are being used for gene
therapy. Take the bad genetic info out of the
virus and replace it with good genes and inject the virus into people that have defective genes.
Vaccinations- weaken or dead viruses are injected into you to promote immunity
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Diseases that are caused by viruses?
Flu H1N1 Chicken Pox Measles HIV Rabies Small Pox Ebola LOTS MORE!!!!
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The HIV Virus