Word: rna
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Like DNA, the RNA molecule has four different chemical groups-called bases -strung along it in sequences like the peaks and notches on a Yale kev. Biologists are convinced that the bases make up a genetic code of four letters-in roughly the same sense that the Morse code of telegraphy has three letters...
Akira Tsugita and Dr. Heinz Fraenkel-Conrat. both of the University of California at Berkeley, tell this week how they pinned a specific chemical change in a virus to a change in the code of its RNA...
Chemical Mutation. Tsugita and Fra«n-kel-Conrat worked with TMU, a virus that causes mosaic disease in tobacco plants. TMU's structure is extremely simple. All it has is a core of coiled-up RNA surrounded by a cylindrical jacket made of protein molecules. Tsugita and Fraenkel-Conrat first stripped off the jacket by use of a protein-dissolving chemical. Then they treated the naked RNA with nitrous acid, which is known to affect the RNA's code-carrying bases. After the nitrous acid had. acted, the RNA was enabled to clothe itself...
...quite the same as the protein of normal virus. And in the specialized world of biochemistry this was exciting news. Other chemically induced mutations have shown themselves as changes of behavior, which cannot be described chemically. Now the effect of the change in the virus's RNA can be seen as a definite chemical change in its protein...
Changing the Code. The report from Tsugita and Fraenkel-Conrat went little farther than that. But Nobel Prizewinning Wendell M. Stanley, head of Berkeley's Virus Laboratory, believes that the original action of the nitrous acid was to change one kind of RNA base into another...