Exon Trapping

Exon trapping is a method to detect the information carrying parts of the DNA, the exons in the laboratory and to distinguish from the non- information bearing portions of the introns.

The algorithmic prediction of exons on the basis of obtained by DNA sequencing data presents itself as extremely difficult because the boundaries of the exons and introns - the so-called splice sites - are strongly degenerate. Also other cis-elements, so-called splice or splice enhancers silencers, the processing of the primary transcripts effect ( see also splicing ).

Because of these problems, the method of exon trapping was developed in order to detect exons can experimentally.

This is based on a plasmid leads to incorporation (see transfection) into eukaryotic cells for the expression of a RNA. This RNA usually contains an intron itself, what the cell is then removed in the course of splicing. An exon (or part thereof) to be found, DNA fragments can be cloned into this plasmid intron indiscriminately. An exon (or part thereof ) is in this DNA fragment, it recognizes the cellular machinery and considered it when splicing. This means that the exon may eventually be found in the finished product and sequenced it (see picture opposite ). Disadvantages: firstly presents the cloning of DNA fragments into the vector and the subsequent analysis because a not insignificant amount of work. On the other exons ( or parts thereof) which may result in, among other things torn out of the natural context, lost that key elements (such as splicing enhancers) and exons are recognized not always reliable.

There are a number of variations of this exon trapping vector, but in principle is based on the principle of the above described theory. Due to the extensive cDNA and EST databases have emerged by now the exon trapping is increasingly losing its importance.

• Biological test method