4. Shape1. Size

3. Nutrition6.Replicatio

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2. Nature 5. StructureGeneral

Properties

•Viruses are minute in size

•They are Ultrafilterable agents

• They are Ultramicroscopic

• Viruses are Obligate intracellular parasite

• Viruses are Pathogenic

•Acellular entity (simple)

• Viruses may be present in crystalline form.

•Viruses are metabolically inert

•Viruses can not cultivated on synthetic media.

Definitions

• Viral protein nature

• Viruses replicate through host cell take over.

• Viruses are geometrically fixed.

• Viruses complete its life cycle only inside the host cell.

• Viral infection may be Reproductive, Non-reproductive or integrated.

• Viral genetic material is only one type of nucleic acid

•Viruses have the genetic material enclosed in a protein capsid

• Viruses are morphologically differ

• Viruses are repeated identical units with known Symmetry

Relative size of viruses

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Complex

Spheroid Elongated

Spheroid& Elongated

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A particle whose atoms are arranged in a more or less constantrelationship to each other (Crick and Watson, 1956)

Viruses are genetic material elements which able to determine aspecific system to transmit from the cell in it they replicate to another (Lauria, 1959)

Viruses are obligate parasitic pathogen, their dimension less than 200 m-micron (Bawden,1950)

Definitions of viruses

Viruses could be surely set as apart from other microorganisms on the bases of five discriminative features:-• Presence of a single type of nucleic acid,• Reproduction from the genetic material only • Incapacity to grow and divide• Absence Lippman”s system • Absence of genetic information required for synthesis of cellular systems (absolute parasite) (Lowff and Tournier, 1967)

Viruses are viruses because they are viruses ( Lowff )

Submicroscopic infectious entities that multiply only intracellularly and are potentially pathogenic (Bawden, 1964)

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