Viruses
Characteristics-
*found in all life forms
*viruses consist of genetic material either DNA or RNA
*are too small to be seen by light
*cannot reproduce outside of a living cell
* not considered free-living
* whole purpose in life to transmit their genetic info from one cell to another for the purpose of replication
Reproduction- A virus must have a hotcell and when they attach the must cross the cell membrane. Once inside the cell the virus replicates itself through a series of events. To complete reproduction the the viruses must exit the cell some virusees bud out of the cell's plasma memberane. Other viruses cause the cell to lyse, releasing newly formed viruses ready to infect other cells. Sitll other viruses pass directly from one cell into an adjacent cell without being exposed to the outside.
Defenitions of prions- A microscopic protein particle similar to a virus but lacking nucleic acid, thought to be the infectious agent responsible for scrapie and certain other degenerative diseases of the nervous system.
Defenition of viroid- An infectious particle, similar to but smalelr than a virus , that consists solely of a strand of RNA and is capable of causing disease in plants.