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4C Viruses. NONLIVING Contain either DNA or RNA (but NEVER Both). VIRUS. Why is a virus considered non-living?. They cannot replicate on their own (without a host cell) They cannot obtain and use energy They cannot respond to the environment. What a virus does. It invades a cell . - PowerPoint PPT Presentation
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4C Viruses
• NONLIVING• Contain either DNA or RNA
(but NEVER Both)
VIRUS
Why is a virus considered non-living?
• They cannot replicate on their own (without a host cell)• They cannot obtain and use energy• They cannot respond to the
environment
What a virus does
It invades a cell.It turns the cell into a virus making
factory until it no longer needs the cell.
It then destroys the cell releasing new viruses to continue the cycle.
How does a virus replicate?
Virus injects it’s genetic info into a host cell. Host cell then “replicates” viral DNA
to makes new viruses
How do they replicate?(replicate means to make more)
LYTIC CYCLE
Lysogenic CycleWait for animation
LYTIC CYCLE
• destroys host cell in a short amount of time
LYSOGENIC CYCLE
• takes longer to destroy host cell
Both Cycles Together
Types of Viruses
• Adenovirus• Retrovirus• Bacteriophage
Adenovirus
• any of a group of DNA viruses first discovered in adenoid tissue, most of which cause respiratory diseases
Retroviruses• Made of RNA• Inject their RNA into
the host cell• Host cell makes it into DNA• Viral DNA joins the host DNA• Viral DNA pirates the cell and forces the cell
to make new viral RNA and new viruses
HIV is a retrovirus
Bacteriophage
Virus that
attacks bacteria
Common Viral Diseases
• Rhinoviruses cause the common cold• HPV (Human papillomavirus) can cause cervical
cancer in women• Herpes simplex viruses cause mouth and/or genital
sores, lesions, and ulcers.• Influenza viruses cause the flu• HIV (Human Immunodeficiency Virus) causes AIDS
and weakens the immune system
Rabies
H1N1
Plant Viruses
How is a disease caused by a virus?
• New viruses made inside BURST out of and destroy host cell
• When your cells die your health is affected
Controlling Viruses
• Antibiotics DO NOT work on viruses.• Most human viral infections can be
fought off by the immune system—boost the immune system with lots of water and rest.
How does a VACCINE work?• Vaccines stimulate the immune
system to create antibodies that recognize a certain virus… • Vaccines inject a small amount of
the virus into your system.
How do vaccines work?• The body then builds antibodies to fight that
specific virus.• Antibodies remember that virus in the future
in case you are exposed to that virus again. • These antibodies patrol your body and if
they recognize that virus…they call in reinforcements and your immune system goes to battle!
Compare viruses to living cellsWhat do they have
in common?
They have DNA & RNA and
They both change over time