Science Forums 2

[tarak]

Viruses are the edge of living and non living substances.
They are obligate parasites an cannot survive outside their host(may be Human being,monkey,dog,even bacteria).Mostly they are highly specific to a host and that makes them cause specific diseases in specific living beings.
Viruses which parasatize on bacteria are called phages.Viiruses are long nucleic acid molecules(DNA or RNA) encapsulated within another capsule like protein molecule.Some viruses are naked and even donot have these protein coats.
Most of the viruses enter living cells and then come to life. By taking over the cellular machinery of thier host they multiply themselves.Viruses change very fast (lie Influenza virus) by modifying thier protein coat and escape from our immunity sytem which recognizes the protein coat.
Now viruses are certainly harmful in thier role as a intracellular parasite but after understanding thier biology we are using them to our benefit in ingenuous ways.
For example the vaccines we use for immunity are mostly made of benign and attenuated form of viral particles.
Similarly some viruses like NPV which cause diseases in insects are used as a natural/biological pesticide for protection of crops.
Viruses are extensively used in genetic engineering as vectors or vehicles for transfer of desirable genes from one system(Bacteria,Jelly fish,Mouse) to another(Corn,Tomato,Human).I have cited only three well known examples but there may be other benefits if viruses are used cleverly.