DNA EVOLUTION AND SUCCESSIVE FILE EDITIONS

Sequences of nucleotides along DNA chains are known to present long ra nge correlations. These correlations are small for simple species (alg ae) and increase for more complex ones. Scanning DNA chains one finds pieces called exons which are known to code some protein sequence, and others called introns whose usefulness is debatable and do not code p rotein sequences. By reading only exons (skipping introns), one always gets no correlation at all, in spite of observing a large correlation by reading the whole DNA sequence. The proposed explanation is that i ntrons are fossil DNA parts no longer in use after evolutional replace ment by new, better material (current exons). Sucessive editions of th e files stored in a diskette follow the same dynamic mechanism propose d for DNA evolution. Current versions of the files play the role of ex ons, whereas introns correspond to old versions no longer in use (but still partially stored on the disk). We find that correlations indeed increase as more and more editions are performed. This artificial syst em has the advantage, over real DNA data, of allowing experiments. (C) 1998 Elsevier Science B.V. All rights reserved.