Download Virus Notes - Lake Stevens School District

Viruses are particles of
nucleic acid, protein,
and lipids that invade
living cells and
reproduce. They are
composed of a core
of DNA or RNA
surrounded by a
protein coat called a
capsid.
 Examples of Viruses:
Influenza, colds,
chicken pox, measles,
polio, and AIDS.

 1.
Shape – they come in a variety of
shapes. (see next slide)
 2. Size 20-400 nanometers.
1 nanometer = 1 billionth of a meter.
 3. Specificity = certain viruses only
infect certain organisms…your dog
can’t get chickenpox!
Retroviruses: Contain
RNA as their genetic
information. It is then
copied to DNA. This is
“backwards” or
“retro”.
 Viruses are
considered parasites
because they must
infect a living cell in
order to grow and
reproduce.

1. Lytic Infection – a
virus enters a cell,
makes copies of itself
and causes the cell
to burst
 Attaches, entry,
replication, assembly
and release
 http://www.npr.org/t
emplates/story/story.
php?storyId=1140750
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
 Lysogenic
Infection
– a virus integrates
its DNA into the
DNA of the host
cell. It many
remain inactive for
a period of time.
 The viral DNA is
called a
prophage.

1. Vaccine – a
weakened dose of
the virus. When
injected it usually
prompts the body to
produce an immune
reaction to prevent
illness.

2. Interferon –
proteins that prevent
virus from attaching
to your cells and
reproducing.

3. Antibodies – immune system proteins
that attack and kill bacteria and viruses.