GLOBAL DINUCLEOTIDE SIGNATURES AND ANALYSIS OF GENOMIC HETEROGENEITY

zeEarly biochemical experiments measuring nearest neighbor frequencies established that the set of dinucleotide relative abundance values (d inucleotide biases) is a remarkably stable property of the DNA of an o rganism. Analyses of currently available genomic sequence data have ex tended these earlier results, showing that the dinucleotide biases eva luated for successive 50 kb segments of a genome are significantly mor e similar to each other than to those of sequences from more distant o rganisms. From this perspective, the set of dinucleotide biases consti tutes a 'genomic signature' that can discriminate sequences from diffe rent organisms. The dinucleotide biases appear to reflect species-spec ific properties of DNA stacking energies, modification, replication, a nd repair mechanisms. The genomic signature is useful for detecting pa thogenicity islands in bacterial genomes.