Now the DNA operating system of a species is very very old indeed, and there is evidence that it, seen in the long term, does something a bit like the computer with its disc files. Part of the evidence comes from the fascinating phenomenon of 'introns' and 'exons'. Within the last decade, it has been discovered that any 'single' gene, in the sense of a single continuously read passage of DNA text, is not all stored in one place. If you actually read the code letters as they occur along the chromosome (i.e. if you do the equivalent of breaking out of the discipline of the 'operating system') you find fragments of 'sense', called exons, separated by portions of 'nonsense' called introns. Any one 'gene' in the functional sense, is in fact split up into a sequence of fragments (exons) separated by meaningless introns. It is as if each exon ended with a pointer saying 'continued on page 94'. A complete gene is then made up of a whole series of exons, which are actually strung together only when they are eventually read by the 'official' operating system that translates them into proteins.
