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Differential distribution of simple sequence repeats in eukaryotic genome sequences
M V Katti1, P K Ranjekar, V S Gupta
1Plant Molecular Biology Unit, Division of Biochemical Sciences, National Chemical Laboratory, Pune, India.
Molecular Biology and Evolution
|June 23, 2001
Summary
This study analyzed genome sequences for DNA repeats, finding dinucleotide repeats are generally longest. Repeat abundance suggests DNA repair and replication machinery, not just sequence composition, influences their formation.
Area of Science:
- Genomics
- Molecular Biology
- Bioinformatics
Background:
- Repetitive DNA sequences are common in genomes.
- Understanding the factors that influence repeat occurrence and length is crucial for genome analysis.
Purpose of the Study:
- To analyze the occurrence and characteristics of various DNA repeat types (mono-, di-, tri-, tetranucleotide) across different species' complete genomes.
- To investigate factors contributing to the abundance and length variation of these repeats.
Main Methods:
- Comparative analysis of complete genome sequences from humans, Drosophila melanogaster, Caenorhabditis elegans, Arabidopsis thaliana, and Saccharomyces cerevisiae.
- Identification and quantification of mono-, di-, tri-, and tetranucleotide repeats.
- Analysis of coding DNA sequences to assess codon repeat tolerance.
Main Results:
- Dinucleotide repeats were consistently longer than other repeat types across all studied genomes.
- Tetranucleotide repeats in humans and trinucleotide repeats in Drosophila also showed increased length.
- Repeat density varied between chromosomes within species, and repeat abundance could not be solely explained by nucleotide composition or DNA structure potential.
- Expansions of codon repeats encoding small hydrophilic amino acids were more tolerated in coding sequences than those encoding hydrophobic or basic amino acids.
Conclusions:
- The formation of DNA repeats is likely influenced by DNA replication, repair, and recombination machinery, in addition to nucleotide composition.
- Selection pressures act on codon repeats in coding regions, favoring those encoding hydrophilic amino acids and eliminating those encoding hydrophobic/basic amino acids.