viruses

media type="youtube" key="Yrc6dOD9s8E&hl=en&fs=1" height="344" width="425" __**What are viruses?**__
 * Virus from the latin meaning toxic and poison is a sub-microscopic infectious that is unable to grow or reproduce outside a host cell. Each viral consists of genetic material, DNA with a protective protein coat called caspid. Viruses infect all cellular life forms.**
 * Viruses are very small forms of microbes. There is a big discussion if they are alive or dead as they don't carry out some life processes (MRS GREN) but viruses are very fast in reproducing. Viruses are parasites which means they can only live inside living cells.**
 * Viruses are always pathogens because they damage their host cells. Viruses will not grow on nutrient agar jelly as the agar jelly is not a living thing.**

__**Structure**__
 * 1) **Viruses are so tiny they pass through the filters that catch blood cells and bacteria and can only be seen with a high powered electron microscope**
 * 2) **Viruses come in many shapes similar to te appearances of bacteria -rod,spheres,threads and other forms.**

__**They are made of 2 parts**__


 * -a piece of genetic material**
 * -a protein case**


 * __Reproduction__**

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 * Viruses use living cells from plants and animals to reproduce. There are 6 main steps to viral reprodution:**
 * step 1 -virus attatches itself to the wall of the host cell**
 * step 2 -viral genes are injected into the cell...**
 * step 3-...and move to the nucleus**
 * step 4-viral genes cause cells to make many copies of the virus**
 * step 5- Coats are produced that form the outside of a virus.**
 * step 6-cell ruptures and newly assembled viruses escape**
 * This process is called //Replication//**
 * __Diseases__**
 * Examples of common human diseases caused by viruses are:**
 * common cold
 * influenza
 * chickenpox
 * cold sores
 * AIDS

__Culturing Viruses__ Viruses can only be cultured inside living cells.Unlike bacteria and fungi ,viruses cannot be cultured on an agar plate.

Some information was taken from -Year 11 Study Guide NCEA Level 1 Science Authors-Brenda Hannay,Paul Howison and Mark Sayes-Year published 1988-Printed in New Zealand Pages 53-54

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