In late 1955, and early 1956, Paul Zamecnik proposed the existence of transfer RNA, a ribonucleic acid like DNA that could form a complement to the genetic strand, and carry its information from the nucleus of the cell out into the cytoplasm, where proteins are made. Zamecnik then announced the discovery of ribosomes, small globular bodies in the cell's cytoplasm that appear to read the stretch of transfer RNA and bring in the amino acid building blocks it specifies to assemble the protein. "It seemed to be a spool on which the reaction took place," Zamecnik said. Then two competing labs were able to put the finishing touches on Zamecnik's idea, decoding the language of transfer RNA and identifying yet another code, messenger RNA, which worked between DNA and transfer RNA. For the next 20 years, Zamecnik turned his attention to research that created a whole new field of inquiry for...