DADA vector. Panel A depicts the situation for conventional fragment length analysis in a standard vector. It can yield either the desired cDNA fragments or any number of wrong fragments stemming from the vector that cannot be distinguished. In Panel B the situation in the DADA vector is shown. The insertion of an approx. 1 kb long vector segment, containing none of the 4 bp cutter sites that are used for the analysis, pushes all of the undesired fragments out of the detection window. Additionally only the cDNA from the 3' end towards the gene is marked with fluorescent dye to avoid signals from vector on the 3' side. Gene variants (e.g. splice variants) can only be discriminated if the variation is located within the most 3' 900 bps of the cDNA sequence.