Possible Origin and Role of Nuclear Introns

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9420422 Hannah Can transposable elements give rise to functional introns? This laboratory has recently demonstrated that the maize transposable element, dissociation (ds) and one copy of the duplicated host sequence can be spliced precisely from the from the primary transcript. In effect, the Ds element has created an intron. A working model of the "intron-late" hypothesis has thus been created and will be tested and characterized by determining the effects of surrounding sequences on Ds splicing, determining the sequence requirements of the 8 bp host duplication on Ds splicing, determining whether fit to consensus of exon/intron borders is needed for Ds splicing and determining whether the Ds-turned intron confers any change on the gene. %%% A controversy exists as to whether introns, sequences which although transcribed from the DNA of (primarily) eukaryotic cells are spliced out to create a functional message, were created early in evolutionary history and served the purpose of providing flexibility in the creation of genes by providing "movable cassettes" or whether they are simply sequences which have been randomly inserted into genes late in evolutionary history and serve no functional purpose. The characterization of a known and well described transposable element in corn as a newly created intron would lend support to the "intron-late" theory. ***