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Ebola Virus
Viruses
1918 influenza virus
Indiana Science Text Pg 52-55
Virus

Virus – Strand of DNA (hereditary
material) surrounded by a protein coat.
Virus

Viruses – Living or Nonliving?
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
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Made up of cells? NO
Grow and develop? NO
Use Energy? NO
Respond to surroundings? NO
Reproduce? YES
NONLIVING
Virus
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Host – Living thing that provides a source
of energy for a virus or organism.
Parasite – Organism that lives in or on a
host and causes harm.
Almost all viruses act like parasites
because they must be inside a living cell
to reproduce AND they destroy the cells in
which they multiply.
Viruses vary in size, but all are much
smaller than cells.
Virus

Active Virus

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
Examples – cold, influenza (flu)
After entering the cell, IMMEDIATELY goes
into action
Virus’s genetic material takes over cell’s
function
Active Virus
1.
2.
3.
4.
5.
Virus attaches to cell
Injects genetic material
into the cell
Cell produces virus’s
proteins and genetic
material
Parts assemble to form
new viruses
Cell bursts when too full
and release new viruses
Hidden Virus
Hidden (latent) Virus
 Example – cold sore
 Doesn’t take action
immediately
Hidden Virus
1.
2.
3.
4.
5.
6.
7.
Virus attaches to a cell
Injects genetic material
Virus’s genetic material
becomes part of cell’s genetic
material.
Virus becomes active.
Cells produce virus’s proteins
and genetic material
Parts assemble to make new
viruses
Cell bursts – releases virus
Effects on other Organisms


Most viruses attach to one kind of host cell
Viruses are transferred by



Air
Objects
A virus that enters bacteria is called a
bacteriophage.
Fighting Viruses



A vaccine is weakened virus particles that
helps you not to be infected by that virus.
The first vaccine was made in 1796 by
Edward Jenner. It was created to fight
smallpox.
Ways to treat a virus include:


Rest
Some medications – Antiviral medications
Research with viruses


Viruses can be good. They are being used
in gene therapy.
Some day, they may cure people with
genetic disorders or cancer using virus to
change DNA.