Sanger sequencing chromatograms of a region in exon 6 of NAGLU gene from a Schipperke with MPS IIIB (forward and reverse) compared to the normal canine sequence (forward). The affected reverse sequence is flipped horizontally to align to the normal. The sequence traces show the poly-A/poly-T and loss of sequence quality, while trying to make it past the poly-A/poly-T insertion. An 11 bp region (boxed) is seen in both the forward and reverse sequences before the poly-A and poly-T respectively, demonstrating a duplication. The 704th codon in the normal forward (CAG) and in the affected forward (CAA) at the junction of the insertion are underlined, it codes for glutamine in both (a synonymous variant). The affected sequence flanking the insertion deduced from the forward and reverse sequences is shown at the bottom of the figure.