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MEWAR UNIVERSITY
SUbjEcT: MIcRobIologY
NAME : pEER zAdA SUhAIl
TopIc: VIRUSES
pRESENTEd To :MR.NAVEd SIR
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We have all gotten viruses…
from bacteria, plants to animals.
Viruses cause colds, flu, warts and diseases such as measles, AIDS and cancer.
AND not all viruses are harmful to humans.
BUT not all viruses cause diseases,
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A VIRUS is either DNA or RNA, that is protected by a protein coat called a CAPSID.
DNA CAPSID
VIRUS
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Why are some viruses harmful?
Virus invades cell
Virus forces cell to make copies of virus
Eventually so many copies are made, the cell explodes,releasing all of the new viruses
When your cells make viruses instead of operating normally, YOU get sick
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DISEASE VIRUSES
AIDS HIV
WartHerpes Simplex Virus
Flu Influenza
Measles Morbillivirus .
Cancer Hepatitis B
Examples of some viral diseases:
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Who do viruses infect?
• Viruses infect Bacteria– These viruses are called bacteriophages
• Viruses infect Plants– One example is the Tobacco Mosaic Virus
• Viruses infect Animals– One example is the common cold
Viruses usually infect a specific host including:
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let’s look at the defining ProPerties of viruses
• Viruses are parasites that invade cells• Viruses have either DNA (Deoxyribose
Nucleic Acid) or RNA (Ribonucleic Acid)• Viruses direct the synthesis of new
virus within a host cell.• Newly made viruses infect other cells.
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If a cell was the size of your classroom, then an average virus would be the size of a softball.
Viruses range in size from 20 nanometers (nm) – 250 nanometers (nm)
1 nm = 0.00000004 inches
10-5 m10-6 m
10-7 m
10-8 m
10-9 m
10-10 m
0 m
virusesanimalcellsbacteriapr
otei
nsat
om
Go five more feet!
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Replication Phases
V - Release- Assembly of virus
DNA and protein coat into whole new viruses
- Leaving the cell
Phase I
Phase II
Phase IV Phase VPhase III
I, II, III - Viruses enter cell- Attachment to cell membrane- Penetration inside cell- Losing virus protein coat
IV - Replication- Tricks cell into making
more viral DNA- Tricks cell into
making viral protein coat
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The concept of a virus as an organism challenges the way we define life:
* Viruses do not breathe.* Viruses do not metabolize.* Viruses do not grow.* However, they do reproduce.
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Are Viruses Living?Create a table where one column represent properties of living organisms and the second column represent properties of a virus.
Properties of Living Organisms
Properties of Viruses
Breathes (respires) Doesn’t breathe
Metabolizes Doesn’t metabolize
Grows Doesn’t grow
Reproduces Reproduces
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The End! And Review• Viruses are very simple: a shell containing
either DNA or RNA.They infect by hijacking cells’ machinery to
force them to make more viruses.• Viruses are tiny, even compared to a cell.• Some viruses may prove useful in gene
therapy as natural carriers of DNA that was specially designed to be good for a particular reason.