Virus of characteristics

 Viruses

The name virus means venom or poisonous fluid was given by pasture.D.J.Ivanowsky  (1892) recognise mosaic disease of  tobacco.

Father of plant virology Beijirinck.

Characteristic of virus

• Virus are non cellular organisms.

• Viruses are obligate parasite. 
• Submicroscopic
• They have either RNA or DNA virus . No virus both contain DNA and RNA.
• they are inert outside their specific host.
• They contain nucleici acid, capable of protein synthesis.

Virus infect plants have single stranded RNA. But in cauliflower mosaic virus double stranded DNA is present.

Virus affect animals  have either single or double stranded RNA or double stranded DNA.

Virus have outer layer capsid.

Capsid is protein coat made of a small units 

called capsomeres.

Central core + capsid are collectively known as nucleocapsid.

These capsomeres arrange in helical or polyhedral geometrical forms.

Bacteriophage or bacterial virus 

• Virus that infect bacteria.
• Bacteriophage was discovered by FW . Twort and named by Felix d'Herelle.
• Bacteriophage are usually double standard DNA virus.
• in QB bacteriophage single stranded RNA is present.

TMV(Tobacco mosaic virus)

• Virus was discovered by the Russian worker D. Ivanowsky(1892).
• It has helical symmetry.

• Having single stranded RNA.
• 5% RNA and 95% protein present in TMV

Hashimoto and co-workers first time reported a virus can be transmitted by insect.

Stanley (1935) crystallize virus for the first time by using ammonium sulphate.