2. Viruses are obligate intracellular, potentially
pathogenic entities, possessing only one type of
nucleic acid either RNA or DNA.
It is surrounded by a protective coat called Capsid.
In some viruses the capsid is surrounded by an
additional spikey coat called the envelope.
The extracellular infective form of virus is called
Virion.
3.
4. It is the process of naming viruses and placing
them into a taxonomic system.
Currently two main classification systems have
been used. They are:
1. ICTV(International Committee on
Taxonomy of Viruses) classification system
2. Baltimore classification system
5. The International Committee on Taxonomy of Viruses began
to devise and implement rules for the naming and
classification of viruses.
Viral classification starts at the level of order and continues as
follows, with the taxon suffixes given in italics:
ORDER(virales)
FAMILY(viridae)
SUB FAMILY(virinae)
GENUS(virus)
SPECIES
6. As of 2012, seven orders,96 families,22
subfamilies,420 genera and 2,618 species of
viruses have been defined by the ICTV.
The seven orders are following:
Caudovirales
Herpesvirales
Ligamenvirales
Mononegavirales
Nidovirales
Picornavirales
Tymovirales
7. The division of the virus into classes based on genome
type and mode of replication and transcription.
Suggested by David Baltimore- Seven Baltimore classes.
Major groups of viruses are distinguished by their
nucleic acid content as either DNA or RNA.
RNA and DNA viruses can be single-stranded (ssRNA,
ssDNA) or double-stranded(dsRNA, dsDNA)
