The Gene: An Intimate History

by Siddhartha Mukherjee

The messenger was generated afresh 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 . . .). The process was akin to a library of rare books that is accessed for translation. The master copy of information—i.e., the gene—was stored permanently in a deep repository or vault. When a “translation request” was generated by a cell, a photocopy of the original was summoned from the vault of the nucleus. This facsimile of a gene (i.e., RNA) was used as a working source for translation into a protein. The process allowed multiple copies of a gene to be in circulation at the same time, and for the RNA copies to be increased or decreased on demand—facts that would soon prove to be crucial to the understanding of a gene’s activity and function.