This document summarizes the morphology and structure of viruses. Viruses are smaller than bacteria and can only reproduce inside living cells. They contain a protein coat called a capsid that encloses their nucleic acid core of either DNA or RNA. Viruses have different symmetries for their capsids including icosahedral, helical, and complex. Some viruses also have an outer envelope. Their genomes may be single or double stranded and circular or linear, determining if they are DNA or RNA viruses.

1. MORPHOLOGY OF VIRUS
BY - NAGUL YOGENDRA S J 20BBT031

2. VIRUS
 A microorganism that is smaller than a bacterium that
cannot grow or reproduce apart from a living cell.
 A virus invades living cells and uses their chemical
machinery to keep itself alive and to replicate itself.

3. HISTORY
 Beijerinck is often called the Father of Virology.
 Two scientists contributed to the discovery of the first virus,
Tobacco mosaic virus. Ivanoski reported in 1892.
 The first human virus to be identified was the yellow fever
virus (1881).

4. Characteristics
 Non living structures.
 Non-cellular.
 Contain a protein coat called the capsid.
 Have a nucleic acid core containing DNA or RNA (one or
the other - not both)
 Capable of reproducing only when inside a HOST cell.

5. MORPHOLOGY OF VIRUSES
 Extracellular infectious viral particle is called “VIRION”.
 Smaller than Bacteria.
 They can not be seen under light microscope hence called
as ‘ultra-microscope’.

6. • The virus particles seen in this manner are known as
“elementary bodies”.
• Viruses are tiny and smaller in its size, ranging between 30-
50 nm. They usually lack a cell wall but are surrounded by a
protective protein coating called the capsid.

7. VIRUS
CAPSID
ICOSAHEDRAL HELICAL
COMPLEX
VIRAL
ENVELOPE

8. VIRAL CAPSID
 Viruses consists of nucleic acid core surrounded by a
protein called capsid.
 Capsid is composed of large number of capsomers which
is made up of polypeptide molecules.
 The capsid with enclosed nucleic acid is known as
nuleocapsid.

9. STRUCTURE :

10. CUBICAL SYMMETRY
 This virus resemble a crystal and are also called
Icosahedral symmetry.
 Icosa-20 (in Greek). Is a polygon with 12 vertices or
corners and 20 sides.
 Each side is in the shape of an equilateral triangle.

11. EXAMPLE :

12. HELICAL SYMMETRY
 The nucleic acid and capsomers are wound together
in the form of helix or spiral.
 Eg : Influenza virus (Enveloped virus) , rabies virus ,
TMV

13. EXAMPLE :

14. COMPLEX VIRUS
• Viruses which do not show either Cubical symmetry
or helical symmetry ,
• Due to complexity of their structure are referred to
have a complex symmentry.
• Eg : Pox virus (variola virus) , Bacteriophage.

15. EXAMPLE :

16. VIRAL ENVELOPE

18. VIRAL ENVELOPE
1
2

19. VIRAL NUCLEIC ACID (GENOME)
• Viruses contain a single kind of nucleic acid either
DNA or RNA which encodes the genetic information
necessary for replication of the virus.
• The genome may be single stranded or double
stranded , circular or linear , segmented or non
segmented.

20. According to Nucleic acid present , viruses can
be classified into :

21. EXAMPLES
DNA VIRUSES
 Pox virus
 Adeno virus
 RNA VIRUSES
 Retro virus
 Coronavirus
NOTE :

22. THANK YOU