Virus- Depends on the host cells that they infect to reproduce. Viruses exist as a protein coat or a capsid, when found outside the host cells. The genetic material found in viruses can be DNA or RNA, but not both. It can be single or double stranded. The virus can insert its genetic material into the host cell, when the genetic material is inserted it can cause uncontrolled growth of the cell, and eventually leads to a tumor formation.
Examples of viruses are:
- Tobacco Mosaic Virus(TMV)
- T4 bacteriophage
- Human Immunodeficiency Virus(HIV)
http://www,ucmp.berkeley.edu/alllife/virus.html
http://www.accessexcellence.org/RC/VL/GG/examples_of_viruses.php
Prions- An infectious protein particle similar to a virus but lacks nucleic acid: thought to be the agent responsible for scrapie and other degenerative diseases of the nervous system.
An example of a prion is:
- CJD(Creutzfeld-Jacob Disease)
http://www.wordnetweb.princeton.edu/per/webwn?s=Prion
http://www.sourcewatch.org/index.php?title=Prion
Viroids- Or virusoid, the smallest of viruses; A plant virus with its RNA arranged in a circular chromosome without a protein coat.
Examples of viroids are:
- Potato spindle tuber viroid- first viroid discovered(1967)
- Coconut cadang- cadang viroid-samll (246 bases) but most virutent.
http://www.wordnetweb.princeton.edu/per/webwn?s=Viroid
http://www.micro.siu.edu/micr302virus.html
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