Correlations in DNA sequences across the three domains of life

We report statistical studies of correlation properties of ∼7500 gene sequences, covering coding (exon) and non-coding (intron) sequences for DNA and primary amino acid sequences for proteins, across all three domains of life, namely Eukaryotes (cells with nuclei), Prokaryotes (bacteria) and Archaea (archaebacteria). Mutual information function, power spectrum and Hölder exponent analyses show exons with somewhat greater correlation content than the introns studied. These results are further confirmed with hypothesis testing. While ∼30% of the Eukaryote coding sequences show distinct correlations above noise threshold, this is true for only ∼10% of the Prokaryote and Archaea coding sequences. For protein sequences, we observe correlation lengths similar to that of “random” sequences.