Genetic Rosetta Stone

The nuclei of reproductive cells are mere blobs of protoplasm, apparently much alike. But each of them contains a genetic "instruction code" that tells it how to develop into a particular sort of creature, ranging from a bacterium to a man. In the case of higher animals, the cell's instructions are carried by long, coiled-up molecules of DXA (deoxyribonucleic acid). In the instance of some viruses, which are the simplest of organisms, the code is found in RNA (ribonucleic acid), which is less complicated.

Knowledge of RNA may lead to understanding of DNA--and few prospects are so likely to thrill the present-day biological, chemical or physical scientist, since in DNA lies the secret of heredity and its illnesses, and of life's very nature. Last week came a significant whiff of success in the study of RNA.

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, dot.

dash and space. The scientists' dearest wish is to break the code in order to find what sequence of bases leads to a given genetic result, such as red hair in humans. Reporting in the Proceedings of the National Academy of Sciences, Dr.

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< This result was not sensational in itself.

Virologists have known for years that judicious chemical treatment will make viruses mutate and change their behavior.

But Tsugita and Fraenkel-Conrat went farther: when they had grown in tobacco plants a good supply of mutated virus, they analyzed its protein and found that it was not 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.

In other words. RNA's genetic code, while still far from unbroken, has at least been changed.

Dr. Stanley thinks that the techniques used by Tsugita and Fraenkel-Conrat may be developed to the point of proving "a Rosetta Stone for the language of life.'' If applied to many mutant viruses, they may break entire genetic codes, telling which groups of bases are responsible for what characteristics. The next step, perhaps years away, will be to do the same with the more complicated molecules of DNA that govern the heredity of higher animals. At some point during this effort.

genetic researchers may discover prevent-atives or cures for hereditary ailments that afflict mankind.

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