““It was the magnesium. The addition of the ion was critical: with the solution supplemented with magnesium, the ribosome remained glued together, and Brenner and Jacob finally purified a miniscule amount of the messenger molecule out of bacterial cells. It was RNA, as expected-but RNA of a special kind. The messenger was generated afreah when a gene was translated. Like DNA, these RNA molecules were built by stringing together four bases-A,G,C, and U (in the RNA copy of a gene, remember, the T found in DNA is substituted for U). Notably, Brenner and Jacob later discovered the messenger RNA was a facsimile of the DNA chain-a copy made from the original. The RNA copy of a gene then moved from the nucleus to the cytosol, where its message was decoded to build a protein. The messenger RNA was neither an inhabitant of heaven nor of hell-but a professional go-between. The generation of an RNA copy of a gene was termed transcription-referring to the rewriting of a word or sentence in a language close to the original. A gene's code (ATGGGCC...) was transcribed into an RNA code (AUGGGCC...).””
