SHORT NOTES ON VIRUS

1. Dr. V. RAMESH
Assistant Professor & Head In-Charge,
Department of Botany,
Vivekananda College,
Tiruvedakam West – 625 234
Madurai
GENERAL CHARACTERS AND
STRUCTURE OF VIRUSES

2. General Characters
1892 – Discovered by Dmitry Ivanosky
1898 – TMV was discovered by Beijerinck
In Latin – virus means – poisons
Viruses are non cellular infectious agents
Reproduce only in living cells
It can be seen only with an electron microscope
Contains core with nucleic acid either DNA or RNA
Core is surrounded by a protein coat (Capsid)
Size is 20- 300 nm
Smallest one is Coliphage F2 (2nm)
Viruses behave nonliving objects because
Can be crystallized, behave as inert chemical outside the host
do not show any syn of metabolism except reproduction
(Replication)
 Considered as link between Living and Non linving things
Types – Phaginae (Infect Bacteria), Phytophaginae (Infect Plants)
Zoophaginae (Infect animals)

3. STRUCTURES OF TMV (TOBACCO MOSAIC VIRUS)
Elongated, rod, 300A° Long & 180A° in diameter
Simple Nucleoproteinaceous structures consists of a central core of genetic
material RNA, Core surrounded by protenacious coat.
Coat is made up of capsomers called nucleo capsid
Total Mol. Weight is 39.4x106
95 % Protein and 5 % RNA, Both are intertwined to form helical, Grooved,
Cylindrical rods of Hollow channel
2130 capsomeres – Capsid 3 turns – 49 capsomers
130 turns – 2130 capsomers, capsomers - 17400 weight
Capsomers have a furrow on inner side to form – helical groove
 RNA Strand embedded in that furrow
RNA – 6400 Nucleotides (Nucleotides : Capsomers ratio is 3:1

4. CORONA VIRUS

7. Thank You All