The computer Viruses, Lecture notes of Technology

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Obligate Intracellular Parasites – only

demonstrate characteristics of life while

“inside” a host cell: Bacteria, animal, plant

Outside a host cell, inert, no enzyme or other activity Inside a host cell – viral Nucleic Acid (DNA or RNA) takes over the cell and directs the cell to produce new virus particles (replication) Size of Viruses: See page in text 155?, very tiny (picorna) to huge (pox viruses)

Types of viruses based on “morphology” – shape; structure Helical (like TMV or Ebola) Polyhedral (adeno and polio) Enveloped (flu) and Complex (bacteriophage)

EBOLA

Influenza A: Enveloped, with spikes, RNA, multisegmented

genome (8 separate pieces of RNA)

Bacteriophage: Complex

Cultivation of viruses: need living cells, living hosts Tissue cultures, embryonated eggs, bacterial cultures

Cultivation of viruses: need living cells, living hosts Tissue cultures, embryonated eggs, bacterial cultures Bacteria grown as a “lawn” – and viruses are in the clear zones, plaques

Viral replication in bacteria – life cycle of bacterial virus

Lysogneic (latent) cycle, genome of virus incorporated into

host cell genome “infected with seeds of destruction”

Animal Virus Life Cycle: Penetration, Uncoating, Biosynthesis, Assembly, Maturation, Release Can have Latent infection also.

Animal Virus Life Cycle: Penetration, Uncoating, Biosynthesis, Assembly, Maturation, Release Can have Latent infection also. Latent infection is seen in herpes type and even HIV Hiv is a RNA virus, a “retrovirus” with an enzyme called reverse transcriptase “ causes DNA to be synthesized from genome that is RNA (backwards) The Drug AZT works on HIV by inhibiting this enzyme

Budding of an animal virus from a host cell

Multi-segmented RNA genome of Influenza: higher mutation

rate, genetic shift and drift, new vaccines required

Prions: Infectious proteins, cause scrappie in sheep, Kuru in

humans, BSE in cattle, and KJD in people (mad cow in

humans)

Watch the video “The Brain Eaters” Spoingioform encephalopathy