High statistics block entropy measures of DNA sequences

Area of Science:

• Genomics
• Bioinformatics
• Molecular Biology

Background:

• DNA sequences exhibit inherent inhomogeneities and uneven word frequencies.
• Understanding short-range correlations is crucial for genomic analysis.
• Previous studies have explored base composition but lacked detailed correlation insights.

Purpose of the Study:

• To investigate short-range correlations in DNA sequences using an improved block-entropy measure.
• To analyze genomic composition homogeneity in various organisms like S. cerevisiae, viruses, organelles, and E. coli.
• To identify deviations from randomness in dinucleotide and tetranucleotide frequencies.

Main Methods:

• Application of an improved block-entropy measure for analyzing DNA sequences.
• Comparative analysis of whole chromosomes and large genomic regions.
• Examination of base composition homogeneity and nucleotide frequency distributions.

Main Results:

• Despite local sequence variations, entire chromosomes and large genomic regions display bulk composition homogeneity.
• Selection, mutational pressure, and recombination appear to homogenize DNA base composition within genomes.
• Significant deviations from randomness were observed in SW (C,G/A,T) dinucleotide and RY (A,G/C,T) tetranucleotide frequencies for E. coli and S. cerevisiae.

Conclusions:

• Genomic evolutionary pressures act to homogenize DNA base composition, though their specific mechanisms vary across organisms.
• SW dinucleotide and RY tetranucleotide frequencies are key indicators of non-randomness in specific genomes.
• The improved block-entropy measure provides valuable insights into genomic sequence organization and evolutionary processes.