Essay on virus

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Virus Overview

The virus was first thought about in 1883 when A. Mayer was seeking to find the cause of the tobacco mosaic disease. Though he was unable to see them with the microscopy of his day, he postulated that a small agent caused the disease. D. Ivanowsky, later tried tests as well and also concluded that it was a disease caused by something smaller than they could see. The virus was first found and discovered in 1935 by Wendell Stanly. He was able to crystallize the virus, now known as the tobacco mosaic virus.
The smallest viruses are only 20 nm in diameter, smaller even than a ribosome in a cell. Though not a living thing, viruses are infections particles
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Once control of the cell is achieved, the genes tell the cell to start producing more viral parts and assemble them. Eventually, so many new viruses are produced, the cell swells and eventually bursts, spewing hundreds or even thousands of new viruses.
The lysogenic cycle, is nearly the same as the lytic cycle, though a bit more controlled and hidden. The gene code splices into the cells code and lies dormant, waiting for the time to then begin producing itself. This way, the cell does not die after infection until the genes take over and begin the lytic cycle.
Many variations on the viral infect scheme are among animal viruses. There are two variations, viruses with envelopes and viruses with RNA genomes, though some have both of these features.
Classes of Animal Viruses dsDNA Papilloma, Herpes, Small Pox ssDNA Parvovirus dsRNA Diarrhea viruses ssRNA + Poliovirus ssRNA - Rabies, measles ssRNA DNA leukemia

Viruses with an envelope outside the capsid use the membrane to help enter the host cell. This membrane is generally a lipid bilayer, with glycoproteins protruding from the surface.
The viruses that infect humans
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