NUCLEOTIDE COMPOSITION EFFECTS ON THE LONG-RANGE CORRELATIONS IN HUMAN GENES

We use the wavelet transform to investigate the fractal scaling proper ties of coding and noncoding human DNA sequences. We find that the str ength of the long-range correlations observed in the introns increases with the guanine-cytosine (GC) content, while coding sequences show n o such correlations at any GC content. However, we demonstrate that lo ng-range correlations can be detected when the coding sequences are un dersampled by retaining the third base of each codon only. This strong ly suggests that the observed correlations are not likely to be due to insertion-deletion mechanisms. We comment about the origin of these c orrelations in terms of putative dynamical processes that could produc e the isochore structure of the human genome.