Defective (nonautonomous) copies of transposable elements are relatively common in the genomes of eukaryotes but less common in the genomes of prokaryotes. With regard to transposable elements that exist exclusively in the form of DNA (nonretroviral transposable elements), nonautonomous elements may
Evolutionary dynamics of transposable elements in prokaryotes and eukaryotes
β Scribed by D. A. Hickey
- Publisher
- Springer Netherlands
- Year
- 1992
- Tongue
- English
- Weight
- 591 KB
- Volume
- 86
- Category
- Article
- ISSN
- 0016-6707
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β¦ Synopsis
This paper summarizes some recent theories about the evolution of transposable genetic elements in outbreeding, sexual eukaryotic organisms. The evolutionary possibilities available to self-replicating transposable elements are shown to vary depending on the reproductive biology of the host genome. This effect can be used to explain, in part, the differences in abundance of transposable elements between prokaryotes and eukaryotes. It is argued that the pattern of sexual outbreeding seen in mammals and plants is especially favorable to the spread of transposons. Moreover, because transposon spread is facilitated by zygote formation, the evolutionary origin of sexual conjugation may have been due to selection on transposon-encoded genes. Finally, evidence is also presented that introns could have originated as transposable genetic elements.
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## Abstract Autonomous transposable elements, generally considered as junk and selfish, encode transposition proteins that can bind, copy, break, join or degrade nucleic acids as well as process or interact with other proteins. Such a repertoire of activities might be of interest for the host cell.
Previous models of the evolution of selfish transposable genetic elements have failed to include the possibility that transposition may be limited by shortage of a host-encoded factor. The titration of host factors may be important in limiting the rate of transpositional increase in these elements.
Recent studies have demonstrated that transposable elements in maize and Drosophila are spliced from pre-mRNA. These transposable element introns represent the first examples of recent addition of introns into nuclear genes. The eight reported examples of transposable element splicing include member