Detection of transcripts containing the predicted 3'UTR extension. A. Schematic overview of the validation PCR setup. For each of the eight tested genes, two primer pairs were designed with the forward primer in common. The reverse primer was binding either within the known 3' UTR region (reverse short) or in the predicted extension (reverse long). Amplified regions were termed S (short) or L (long), respectively and the expected size of these fragments for each of the genes is displayed below. In case of false positive prediction, no PCR fragment is expected for the L fragment, since the reverse long primer then has no template to bind to. Contamination of genomic DNA was excluded because primer pairs were spanning at least one intron. B. Results of PCR amplification visualized by gel electrophoresis. For each gene, four lanes represent amplification of the short and long fragment in two tissues: liver and muscle. Next to these four lanes a size marker was included with corresponding fragment sizes indicated left of the image.