Notes
pg. 455-461
Biologists first suspected the existence of computer computer viruses near the end of the ordinal century. At that time, European scientists were seeking to identify the infectious component responsible for tobacco mosaic disease, a disease that stunts the gain of tobacco plants and makes their leaves blotchy. One experiment used fine-pored porcelain filters to strain bacterium from sap extracted from infected tobacco plants. The pores in these filters were so wee that bacteria could not pass through them. However, the infectious instrument passed through the filters without difficulty. Scientists concluded that the infectious agent must be smaller than a typical bacterial cell. After upgrade investigation, the scientists found that the agent could reproduce only inside the surviving cells it infected. They called the agent a virus, a Latin word sum poison.
The true nature of viruses was discovered in 1933 when the biologist Wendell Stanley of the Rockefeller lend tried to purify an extract of the tobacco mosaic virus (TMV). To his great surprise, the purified TMV extract formed crystals, a quality of chemicals. Stanley concluded that TMV is chemical matter rather than a living organism.
Within a few years of Stanleys findings, scientists were open to break TMV and confirm his conclusion. TMV is a chemical, not a cell. Each particle of TMV is made of only cardinal kinds of molecules: the nucleic acid RNA and protein.
TMV consists of a core of RNA surround by a coat of protein. Later scientists were able to secern the RNA from the protein. When they reassembled the two components, the reconstructed TMV particles were adepty able to infect healthy tobacco plants.
The chemicals were the virus itself, not merely derivatives of it. Through this experiment and others, a general picture of virus structure and function has emerged. A virus is...
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