Word: mycoplasmas
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Dates: during 1980-1989
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...among organisms were thought to involve only the number and type of proteins that are strung together. Now researchers in the U.S., Europe and Japan have found species + that defy certain words in the genetic scripture: in the familiar Paramecium, a single-celled protozoan, and in a bacterium called Mycoplasma capricolum, the DNA patterns responsible for protein construction exhibit a surprising difference. Not only does the discovery undermine the "universality" of the genetic code, but it may cause scientists to rethink certain theories about evolution...
...Paramecium's cellular machinery read either of two "periods" (TAG and TAA) in the standard code, it linked the amino acid glutamine onto the protein chain rather than stopping production; it obeyed only the third word for stop, TGA. At Nagoya University in Japan, scientists have found that Mycoplasma also ignores a stop triplet. But in this case it is TGA that is translated into an amino acid, tryptophan, while the other two codons are read as stop. "Within a certain sphere," says Biologist Syozo Osawa, "it seems that change is possible...