WHAT NOT TO BE WHAT NOT TO BE STUDIED TODAYSTUDIED TODAY

COMPUTER VIRUS VIRU Sahastrabuddhe

Sub microscopic entity

consisting of a single nucleic

acid surrounded by a protein

coat and capable of

replication only within the

living cells of bacteria,

animals or plants.

WHAT ARE VIRUSES?WHAT ARE VIRUSES? IN LATIN, VIRUS MEANS POISON VIRUS ARE SUBMICROSOPIC ENTITIESTHEY ARE NON CELULARVIRUSES LACK PROTEIN SYNTHESIS

MACHINERYVERY MUCH DEPENDANT ON HOSTS FOR

THEIR MULTIPLICATIONMOSTLY HAVE RNA AS THE GENETIC

MATERIAL BUT DNA MAY ALSO BE PRESSENT IN SOME CASES BUT NOT BOTH.

THEY ARE INCAPABLE OF METABOLISMTHEY SHOW NO INCREASE IN SIZE

HE, WAS THE ONE

WHO FIRST TIME

DISCOVERED VIRUS

(TOBACCO MOSAIC VIRUS)

VIRUSES CAN BE CLASSIFIED ON THE FOLLOWING CRITERIA:

FORM OF CAPSID:o HELICALo ICOSAHEDRALo COMPLEX NUCLEIC ACID:o DNAo RNA PRESENCE OF ENVELOPEo NAKEDo ENVELOPED

IT IS A PROTEIN COAT OF THE VIRUS COMPRISED OF MONOMERS CALLED ‘CAPSOMERES’

THESE ARE SPIKES THAT ARE LOCATED ON THE CAPSID OR ON ENVELOPETHESE HELP THE VIRUS TO ATTACH TO THE HOST CELLTHEY ARE NOT FOUND IN ALL VIRUSES

IN SOME VIRUSES, A COVERING OVER THE NUCLEOCAPSID IS SEEN.THIS CAPSID IC MADE UP OF LIPOPROTEIN BILAYER.

IT MAY BE COMPRISED OF DNA OR RNA, MOSTLY- RNA

BACTERIOPHAGEBACTERIOPHAGE

BACTERIOPHAGE INFECTING BACTERIOPHAGE INFECTING BACTERIABACTERIA

A VIRUS ATTACKS THE HOST CELL IN THE FOLLOWING ORDER:

• LANDINGLANDING• ATTACHMENTATTACHMENT• TAIL CONTRACTIONTAIL CONTRACTION• PENETRATION & UNPLUGGINGPENETRATION & UNPLUGGING• NUCLEIC ACID INJECTIONNUCLEIC ACID INJECTION

MECHANISM OF VIRAL MECHANISM OF VIRAL ATTACKATTACK

LANDINGLANDING

ATTACHMENTATTACHMENT

TAIL CONTRACTIONTAIL CONTRACTION

PENETRATION & PENETRATION & UNPLUGGINGUNPLUGGING

NUCLEIC ACID NUCLEIC ACID INJECTIONINJECTION

LYTIC CYCLELYTIC CYCLEVIRUSES REPLICATE THROUGH THE LYTIC CYCLE. BUT MAY ALSO ENTER INTO THE LYSOGENIC PHASE.VIRUSES IN EXTRACELLULAR CONDITION ARE INACTIVE BUT ONCE THEY ENTER THE HOST CELL, THEY BECOME VERY ACTIVE

LYTIC CYCLELYTIC CYCLE

Respiratory transmissionInfluenza A virus

Faecal-oral transmissionEnterovirus

Blood-borne transmissionHepatitis B virus

Sexual TransmissionHIV

Animal or insect vectorsRabies virus

VIRUSES LACK THE PROTEIN SYNTHESIS MACHINERY, HENCE THEY CANNOT REPLICATE WITHOUT ABSORBING NUTRIENTS FROM HOST BODYTHIS IS THE REASON WHY VIRUSES ARE TERMED AS OBLIGATE INTRACELLULAR PARASITES.

REPLICATIONREPLICATION