VIRUSES

1. A virus is a tiny nonliving particle that enters and then reproduces inside a living cell. They can multiply but only when inside a cell. Shapes 1. Round- chickenpox virus causes an itchy rash on human skin 2. Robotlike – bacteriophage virus that infect bacteria “bacteria eater” 3. Tube-shaped tobacco mosaic viruses infect tobacco plants 4. Round – West Nile virus in animals 5. Bullet-shaped virus such as rabies infects the nerve cells in animals Two basic parts of a virus particle 1. Protein coat – protects the virus particle 2. Inner core – genetic material How it Multiplies 1. Attaches to a host, much like a parasite, and enters the cell (host) 2. The viruses genetic material takes over many of the cells functions 3. The virus instructs the cell to produce the virus’s proteins and genetic material. 4. These proteins and genetic material assemble into new viruses. Some viruses take over cell function immediately, some viruses wait for a while. VIRUSES

2. Active Viruses-after entering a cell, these viruses go to action immediately Hidden Viruses- these viruses “hide” for a while and may stay inactive for years. Once conditions are right, the cell bursts open and symptoms begin to appear. Examples: cold sores which may be activated by sunlight or high stress levels. 5. When the cell is full of the copied proteins and genetic information from the virus, the cell explodes and the viruses are released. 6. Releases viruses go on to infect more cells. 5. Diseases 1. People (AIDS, cold) 2. Plants ( mosaic virus causes less fruit production) 3. Dogs ( rabies and distemper) 6. Usefulness 1. Gene therapy