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Updated: May 2, 2026

Determination of the Optimal Chromosomal Locations for a DNA Element in Escherichia coli Using a Novel Transposon-mediated Approach
Published on: September 11, 2017
Accommodating the load: The transposable element content of very large genomes
Cushla J Metcalfe1, Didier Casane2
1Instituto de Biociências; Universidade de São Paulo; Cidade Universitária; São Paulo, Brazil.
Large eukaryotic genomes, often exceeding 20 Gb, are rare and contain abundant transposable elements (TEs). Lungfish and salamanders accommodate large genomes due to gradual TE accumulation and inactivation over time.
Area of Science:
- Genomics
- Evolutionary Biology
Background:
- Very large genomes (>20 Gb) are found across eukaryotes but not in excavates.
- A positive correlation exists between genome size and transposable elements (TEs).
Purpose of the Study:
- To investigate the composition and characteristics of very large genomes in eukaryotes, focusing on transposable elements (TEs).
- To compare TE diversity and abundance in lungfish and salamander genomes with those of other taxa.
Main Methods:
- Analysis of genome composition, specifically identifying and quantifying transposable elements (TEs) like retrotransposons.
- Comparative analysis of TE profiles across different taxa with large genomes.
Main Results:
- In lungfish and salamanders, 25-47% of genomes consist of identifiable retrotransposons, with distinct TE classes in each.
- The majority of large genomes in angiosperms, gymnosperms, and dinoflagellates were unidentified, potentially novel TEs.
- Unlike large-genome plants, lungfish and salamanders do not show increased extinction risk.
Conclusions:
- Large genomes in lungfish and salamanders are likely shaped by gradual TE proliferation, inactivation, and decay over long evolutionary periods.
- The diversity and abundance of TEs vary among taxa with large genomes, similar to smaller genomes.
- Inactive, divergent TE copies may constitute the 'missing' portions of lungfish and salamander genomes.
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