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1. A virus is an infectious agent made up of nucleic acid
(DNA or RNA) wrapped in a protein coat called a capsid.
2. Viruses have no nucleus, no organelles, no cytoplasm
or cell membrane—Non-cellular
3. This is why it does NOT belong to any kingdom.
vs
Replication is how a virus spreads.
A virus CANNOT reproduce by itself—it must invade a host
cell and take over the cell activities, eventually causing
destruction of the cell and killing it. (The virus enters a cell,
makes copies of itself and causes the cell to burst releasing
more viruses.)
DNA/RNA is
Virus attaches
to cell.
DNA/RNA injected
into cell.
Step 3
Step 2
Step 1
Virus copies
itself.
Step 4
copied.
Cell bursts (lyses) and
releases new viruses.
Step 5
Certain viruses can only attack certain
cell types. They are said to be specific.
Example: The rabies virus only attacks brain or nervous cells.
Surface Markers
Virus
Receptor Sites
It’s like the pieces of a puzzle. The
ends have to match up so only
certain pieces fit.
Cell
A virus recognizes cells it can infect by
matching its surface marker with a
receptor site on a cell.
Virus
Surface
Markers
Receptor
Sites
Cell
1. Bacteriophage—viruses that infect
bacteria
Capsid (protein coat)
2. Flu (influenza), HIV
– inside contains either
RNA or DNA
DNA or RNA
Surface
Marker
Capsid (protein coat)
THE FIVE VIRUSES MODELED IN LAB ACTIVITY:
Animals, plants and bacteria are all susceptible to viruses.
HIV
Potato X
Adenovirus
Tobacco Mosaic
Bacteriophage
NANO
*•PIN • 1x *
VIRAL VECTORS
MOSQUITO
Carrier of West Nile Virus. When fall arrives and
temperatures decrease, the mosquito population
consequently declines. However, migration season
is shortly after, and as birds and mosquitos travel,
they bring the virus with them. There are currently
110 species of infected birds, and the number of
mosquito species who can transmit the virus has
jumped from one to eight.
BATS
Carrier of the Rabies virus. It is a preventable viral
disease of mammals most often transmitted through
the bite of a rabid animal. The overwhelming
majority of rabies cases reported to the Centers for
Disease Control and Prevention (CDC) each year
occur in wild animals like raccoons, skunks, bats
and foxes.
NON-VECTOR VIRAL DISEASES
Tobacco leaves and tomatoes
infected with Tobacco Mosaic Virus
POTATO X VIRUS