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Rapid sequence turnover at an intergenic locus in Drosophila
Nadia D Singh1, Dmitri A Petrov
1Department of Biological Sciences, Stanford University, Stanford, California, USA. ndsingh@stanford.edu
Molecular Biology and Evolution
|January 24, 2004
Summary
Genome size in Drosophila appears stable, but intergenic DNA rapidly turns over. Small deletions dominate DNA loss, while infrequent insertions drive DNA gain, challenging passive inheritance models for unconstrained DNA.
Area of Science:
- Evolutionary biology
- Genomics
- Molecular evolution
Background:
- Drosophila species exhibit similar genome sizes, despite intergenic DNA being potentially unconstrained.
- Unconstrained DNA is unlikely to be passively inherited due to a bias towards deletions over insertions.
Purpose of the Study:
- Investigate the evolutionary dynamics and maintenance of intergenic DNA.
- Reconstruct the length evolution of a specific intergenic locus in the Drosophila melanogaster species complex.
Main Methods:
- Sequencing of a 1.2-kb intergenic locus across four closely related Drosophila species.
- Analysis of insertion and deletion events, including nuclear transposition of mitochondrial sequences and DNAREP1_DM transposons.
Main Results:
- The locus shows size similarity across species, but less than 10% of ancestral sequence remains.
- The region expanded via insertions in the common ancestor and has been shrinking since lineage split.
- No evidence for size maintenance; dynamic equilibrium between deletions and insertions observed.
Conclusions:
- Apparent genome size stability in Drosophila masks rapid sequence turnover at intergenic loci.
- Intergenic DNA evolution is driven by a dynamic equilibrium, not passive inheritance.
- Small deletions and sporadic large insertions shape intergenic region evolution.