Genomic signature: Characterization and classification of species assessedby chaos game representation of sequences

We explored DNA structures of genomes by means of a new tool derived from t he "chaotic dynamical systems" theory (the so-called chaos game representat ion [CGR]), which allows the depiction of frequencies of oligonucleotides i n the form of images. Using CGR, we observe that subsequences of a genome e xhibit the main characteristics of the whole genome, attesting to the valid ity of the genomic signature concept. Base concentrations, stretches (runs of complementary bases or purines/pyrimidines), and patches (over- or under expressed words of various lengths) are the main factors explaining the var iability observed among sequences. The distance between images may be consi dered a measure of phylogenetic proximity. Eukaryotes and prokaryotes can b e identified merely on the basis of their DNA structures.