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What proved most significant about Berg's experiment, and helped win the prize, were the steps that immediately preceded it. The virus he wanted to introduce into the bacterium was itself a hybrid. By ingenious use of enzymes that can cut, patch and join nucleic acids, he and his colleagues managed to splice DNA from a bacterial virus into SV40's genes, forming a single closed loop. That was the first time scientists had been able to link the genes of two distinctly different species, and thus created the prospect of producing entirely new life forms.
Gilbert and Sanger vastly advanced the new technology of recombinant DNA, as it has become known, with their different methods for determining the sequence of nucleotides, or chemical "letters," that carry the message in the long-chained DNA molecules. Gilbert's technique, devised with his Harvard colleague Allan Maxam, is essentially chemical: it uses reagents, or chemical markers, to test for different nucleotides along the molecule. Sanger's is more biological: it employs an enzyme to copy individual "letters" and thus identify them.
These techniques have eased the way for all sorts of gene splicing. By the insertion of appropriate new genes, bacteria have already been "taught" to produce interferon, the antiviral substance that helps the body ward off disease, as well as human insulin. In the offing: gene-replacement therapy for genetic ailments, the creation of new types of plants and industrial enzymes, possibly even an understanding of cancer.