Transcript Viruses & Prions

Viruses & Prions
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What is a virus???
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A virus is neither dead nor alive!
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What is to be alive?
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Characteristics for life...
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1. Metabolism
2. Reproduction
3. DNA
4. Growth & Development
5. Response to environment
6. Maintain internal environment
7. Evolves
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Living organisms do not crystallize - viruses
do.
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Viruses are made-up of either DNA (like
smallpox) or RNA (flu, HIV) and protein. Some
viruses also have
lipids.
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A virus is basically a protein container (capsid)
with nucleic acid inside. The only purpose of
viruses is to
reproduce.
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A virus is not considered alive since it must hijack the
machinery of cells to copy itself.
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Viruses are generally specific as to what they infect.
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Plant viruses like the Tobacco Mosaic Virus, infect
tobacco plants
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Animal viruses like influenza, infect certain animals
(humans, pigs, ducks)
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Viruses that infect bacteria are called a bacteriophage.
Influenza Virus
Tobacco Mosaic Virus
Potato Virus
T4 Bacteriophage
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Viral infection
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When a virus has infected an organisms, there are two
processes that can occur:
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Lytic infection or Lysogenic infection
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In lytic infection - as is the case with bacteriophage T4 a virus enters a cell, makes copies, and causes the
cell to burst (Lyses).
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In lysogenic infection the virus integrates its genetic
material into the DNA of its host. Then the host cell
replicates its DNA along with the viral DNA - thus
producing viruses indefinitely.
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Retrovirus
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These viruses contain RNA instead of DNA as their
genetic material. A retrovirus gets its name "retro meaning backwards" because it copies RNA to DNA.
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Retroviruses can cause cancer in animals and some are
well known such as HIV and Influenza.
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Reverse Transcriptase???
Viroids
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Single-stranded RNA particle without capsid ~ usually
a plant affecting disease.
Retrovirus
Chicken Pox (Varicella)
Measles (MMR)
Smallpox (Variola)
Eradicated, but what about terrorism?
Smallpox
 PRIONS???
Mad Cow Disease or BSE (Bovine Spongiform
Encephalopathy) and varient Creutzfeld-Jacob disease the human form - are thought to be caused by
pathogenic proteins called prions.
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MAD COW DISEASE
Mad cow disease is caused by something called a
"PRION". A prion is a protein that is mutant
(different than the normal kind) and causes
normal proteins to change into mutant proteins
when they come into contact with them.
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These pathogenic (disease causing) proteins can
be obtained by eating tissue that contains it (like
cow brains from an infected cow).
It can also be passed down from mother to
offspring animal ~ cow (inherited). This is
possible because proteins are built from the
instructions found in the organism's genes
(DNA). If the organism has a bad gene for this
disease, it will be passed to the offspring.
The End