Word: rna
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...that only a small percentage of the genes in any cell are giving instructions for the operation of that particular cell. The rest are "turned off" by protein repressers, which wrap themselves around long stretches of DNA and prevent them from transferring their coded information to messenger RNA...
...CONCEPT IS not as farfetched as it sounds. Real viruses are merely segments of DNA (or RNA) surrounded by largely-protein sheaths; they penetrate the cell nucleus (leaving their sheaths behind) and take over the cellular...
...Eventually, the infected cell ruptures, releasing the newly formed viruses to infect other cells. Dr. Howard Temin of the University of Wisconsin has shown that some tumor viruses behave differently. They reverse the normal order of genetic transmission, and with the aid of a recently discovered enzyme, use their RNA messenger molecules to produce DNA, the double-helix master molecule. In a way not yet understood, this triggers the cellular genetic machinery to order cell division, causing the cancerous growth that is then perpetuated in succeeding cell generations...
...Temin thinks he knows why it occurs. According to his hypothesis, normal cells manufacture RNA, which moves to neighboring cells in the form of a protovirus, or template, and stimulates the production of a new form of DNA. But, theorizes Temin, if this wandering RNA somehow transmits the wrong message after entering the cells, it can cause the production of altered DNA that orders the cells to grow abnormally...
...Robert Huebner of the NCI speculates that cancer is caused by a noninfectious virus that is a normal part of every living thing. According to Huebner, the virus, which he has labeled the "C particle," is a part of everyone's genetic heritage, a tiny bit of RNA that is passed vertically from one generation to another and perhaps helps normal development by causing the cells of an embryo to grow. The C particle should become inactive as the fetus matures; if it fails to do so, the result is the rapid cell growth that characterizes cancer...