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DESCRIPTION
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
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BEAUTIFUL but DEADLY
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
vs
3. This is why it does NOT belong to any kingdom.
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
copied.DNA/RNA injected
into cell.Virus attaches to cell.
Virus copies itself.
Cell bursts (lyses) and releases new viruses.
Step 1 Step 2 Step 3
Step 4 Step 5
Certain viruses can only attack certain cell types. They are said to be specific.
It’s like the pieces of a puzzle. The ends have to match up so only
certain pieces fit.
Surface Markers
Receptor Sites
Example: The rabies virus only attacks brain or nervous cells.
Virus
Cell
Surface Markers
Receptor Sites
Virus
A virus recognizes cells it can infect by matching its surface marker with a
receptor site on a cell.
Cell
Capsid (protein coat)– inside contains either RNA or DNA
Surface Marker
DNA or RNA
Capsid (protein coat)
1. Bacteriophage—viruses that infect bacteria
2. Flu (influenza), HIV
HIV
Tobacco Mosaic
Potato X
Adenovirus
Bacteriophage
THE FIVE VIRUSES MODELED IN LAB ACTIVITY: Animals, plants and bacteria are all susceptible to viruses.
BATSCarrier 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.
MOSQUITOCarrier 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.
VIRAL VECTORS
Tobacco leaves and tomatoes infected with Tobacco Mosaic Virus
NON-VECTOR VIRAL DISEASESPOTATO X VIRUS
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