THE CLUSTERED STRUCTURE OF THE PURINES PYRIMIDINES DISTRIBUTION IN DNA DISTINGUISHES SYSTEMATICALLY BETWEEN CODING AND NONCODING SEQUENCES/

A method allowing to measure the inhomogeneous distribution of purines /pyrimidines in nucleotide sequences is developed. We show that this m easure relates to the coding or non-coding character of the considered sequence. Coding sequences present a near to the random Pu or Py dist ribution. This property is shared by both protein-coding DNA and funct ional RNA-coding DNA. Non-coding sequences present a highly clustered inhomogeneity. We propose the hypothesis, corroborated with appropriat e computer simulations, that this is due to the action of various tran sposition events accumulated for long time periods. (C) 1997 Society f or Mathematical Biology.