> A brief word about mRNA

The RNA that encodes our 20,000 genes is called messenger RNA (mRNA) and serves as an intermediate between DNA and protein. Although it might seem as if our 20,000 genes would make only 20,000 proteins, that is not so. It turns out that developing mRNA into protein is a similar process as when an old-fashioned movie producer makes cinema. That is, mRNA records the action from DNA just as the movie studio faithfully develops the film exactly as initially recorded. In the case of DNA transcription, this “first draft” is called the primary transcript.

However, just as the raw footage from a movie shoot is not “translated” directly into a motion picture, in many cases, the “raw” mRNA is also not immediately translated into a protein. Now comes the interesting part: editing. It turns out that mRNA can be “spliced,” much like a movie producer edits and splices movie film once the live shoot is over, organizing the splices into different sequences and leaving some on the cutting-room floor. For spliced mRNA, these sections won’t be translated into protein. This “alternative splicing” means that one gene can give rise to many proteins, just like a movie can have different endings or be edited into a short trailer. Thus, thanks in part to RNA editing, the true molecular diversity of the brain is notably greater than our 20,000 genes.