Term virus originated from Greek Work Virus which means venom or poisnous fluid or toxin molecule. They can’t be separated using bacterial filtre because they are smaller than the bacteria. Chemically, they are nucleic acid bounded by protein capsule.
Discovery of Virus:
- The credit of virus discovery goes to D.J. Ivanowsky (1892). He discovered virus while working on mosaic infected tabacco leaves. F. Twort (1915) and F.d. Herelle (1917) independently discovered the bacteriaophages.
- According to Luria & Dornel (1968), they are the unit in which genome is a nucleic acid. They replicate in the host cell using the cellular facilities to form special particles called virons. They granules are capable to transmit virus genome into other cells.
- According to Matthews (1970), virus consists of one or more templet of nucleic acid (DNA or RNA) which exhibt hereditary characters.
features of viruses :
- Nature of Nucleic acid – RNA or DNA
- Symmetry of the capsid (virus)
- Molecular weight of the virus
- Shape and size (Dimensions) of the viruses
- Presence or absence of envelope.
- Number of chromomeres in the caspid
- Diameter of coiled nucleocaspid and number of cuboid capsomeres.
- Diamter of nucleic acid coiling.
- Interacellular multiplication
- Process of virus transmission.