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Science Frontiers ONLINE No. 22: Jul-Aug 1982 |
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The Nomads Within Us
It was originally believed that human chromosomes were fixed at conception and all subsequent organic development proceeded from the instructions encoded on them. Biologists have recently discovered that genes grasshopper about, constantly modifying genetic instructions -- at least that's the current thinking. Additional modification of genetic instructions seems to be accomplished by entities called "nomads" or "mobile dispersed genetic elements." One type of nomad is a simple ring of DNA called a plasmid. Plasmids seem to be identical to a kind of virus called a retrovirus, which can penetrate into cells and tamper with gene expression; that is, the way genetic instructions are interpreted. Plasmids have been discovered in maize, fruit flies, bacteria, and, now, humans -- and healthy people at that. No one is quite sure what these plasmids do. Even though they look like retroviruses, they may not be associated with illness, but rather help organisms adapt to changing environments. But no one really knows.
(Anonymous; "Human Wandering Genes Can Live on Their Own," New Scientist, 94:18, 1982.)
Comment. So, the human body is not only beset by new genetic instructions and the static introduced by invading viruses and other disease agents, but it has an indigenous population of nomads continually fiddling with our cells' genetic instructions. Our bodies seem more like Grand Central Station with trains loaded with new biological ideas constantly arriving from far and near -- maybe even from outer space a la Fred Hoyle's book Diseases from Space.