Long- and short-range correlations in genome organization

We study the size distribution of coding and non-coding regions in DNA sequ ences. For most organisms we observe that the size distribution P-c(S) of t he coding regions of size S shows short range distribution, whereas the siz e distribution of the non-coding regions follows a power-law decay P-nc(S)s imilar to S-1-mu with power exponents indicating clear long-range behavior. We argue, using the Generalized Central Limit Theorem, that the long-range distributions observed in the non-coding are related to the lower level cl ustering of purines and pyrimidines (1d islands) which follow similar long- range laws. We also address the question of clustering of coding segments i n the two complementary strands of DNA. We observe a short-range clustering of coding regions in both strands, expressed by an exponential decay in th e clustering size distribution. The decay exponent expresses the degree of short-range correlations and the deviation from random clustering.