what is virus
TRANSCRIPT
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.
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