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Heterogeneity of genomes: measures and values
S Karlin1, I Ladunga, B E Blaisdell
1Department of Mathematics, Stanford University, CA 94305-2125.
Summary
Genomic DNA sequences show remarkable similarity within species using dinucleotide relative abundance distances. Specific oligonucleotide patterns reveal compositional extremes across diverse genomes, offering insights into DNA structure and evolution.
Area of Science:
- Genomics
- Molecular Biology
- Bioinformatics
Background:
- Genomic sequences exhibit variations in nucleotide composition.
- Dinucleotide relative abundance distances (delta-distances) and oligonucleotide compositional extremes are key metrics for genomic analysis.
Purpose of the Study:
- To investigate genomic homogeneity across diverse DNA sequences.
- To analyze delta-distances and oligonucleotide compositional extremes in various genomes.
Main Methods:
- Calculation of delta-distances between genomic sequences.
- Analysis of oligonucleotide compositional extremes (e.g., TpA, GpC, CTAG, GATC, CpG, GpG/CpC).
- Comparison of genomic distances within and between species.
Main Results:
- Delta-distances within species are low, only 2-3 times that of random DNA, and smaller than between-species distances.
- Observed oligonucleotide extremes include TpA underrepresentation, GpC overrepresentation in bacteriophages, CTAG underrepresentation in eubacteria, GATC underrepresentation in bacteriophages, CpG suppression in vertebrates and thermophilic bacteria, and GpG/CpC overrepresentation in mitochondrial and chloroplast genomes.
Conclusions:
- Genomic homogeneity is a significant feature within species.
- Oligonucleotide compositional patterns provide insights into DNA structure, mutation, methylation, replication, and repair processes across different life forms.