Viruses

Presented by: Bharat Kumar under supervision Mr. C.M. NAGAR

Contents

1. History of Virology2. Introduction3. Morphology of viruses4. Replication of Viruses

A Brief History of Virology1892 beginning of

virology

Dmitri Iwanowski showed that ceramic filtered extracts from diseased plants could transmit disease to other

plants.

1898

Martinus Beijerinick work on TMV Freidrich Loeffler & Paul Frosch work on foot-and-

mouth disease in cattle

1915-1917

Bacteriophages (eaters of bacteria)Frederick Twort & Felix d’Herelle discovered viruses which infect bacteria.

1880 – Germ Theory

Robert Koch & Louis Pasteur Pasteur

identified rabies to be cause by an agent

he termed “virus” from the Latin for

‘poison’.

WHAT IS VIRUS

A VIRUS is either DNA or RNA, that is protected by a protein coat called a CAPSID.

DNA CAPSID

VIRUS

Viruses are parasites that invade cells.

Who do viruses infect?

• Viruses infect Bacteria These viruses are called Bacteriophages

• Viruses infect Plants One example is the Tobacco Mosaic Virus

• Viruses infect Animals One example is the common cold

Viruses usually infect a specific host including:

Why are some viruses harmful?

Virus invades cell

Virus forces cell to make copies of virus

Eventually so many copies are made, the cell explodes,releasing all of the new viruses

When your cells make

viruses instead of operating

normally, YOU get sick

Viral class and Genome

H-1 parvovirus, lambda X 174

Bacteriophage lambda,

Bacteriophage T4

Cowpea mosaic virus, Poliovirus

Reovirus type 3

Rous sarcoma, Mammary

tumour virus

Hepatitis-B virus, Humans Rodent and Birds

Morphology of viruses

Shape: Cuboid, coiled, bullet shaped, filamentous etc.

Size: Size varies form 20 nm to 30 nm in diameter.

Viral structure: Helical (TMV), Polyhedral (adenovirus), Complex (vaccinia)

Viral envelop: It is made up of protein, lipids and carbohydrates.

Nucleic acid: DNA or RNA.

Deferent type of morphology of viruses

Replication of Viruses

V - Release• Assembly of virus

DNA and protein coat into whole new viruses

• Leaving the cell

Phase I

Phase II

Phase IV Phase V

Phase III

I, II, III - Viruses enter cell• Attachment to cell

membrane• Penetration inside cell• Losing virus protein coat

IV - Replication• viral genome replicates

using the host's cellular machinery

THANK YOU