CORRELATIONS IN DNA-SEQUENCES - THE ROLE OF PROTEIN-CODING SEGMENTS

Protein coding segments (exons) exhibit persistent correlations betwee n their nucleotides with a pronounced period three. It is shown in thi s paper that this periodicity induced by the nonuniform codon usage im plies long-range correlation over hundreds of base pairs if the length distribution of exons is taken into account. We derive expressions wh ich relate the length distribution of exons to the correlation decay a nd find agreement with numerical simulations. Finally, we analyze the decay of the mutual information function in yeast chromosomes, in an E . coli chromosome region, and in myosin heavy chain genes as represent ative examples. It turns out that in these cases we can explain most o f the long-range statistical dependences even quantitatively.