The reaction resulted in successful amplification of exon 7 of the APC gene, producing a single PCR product of the expected amplicon size. The PCR product was excised from the agarose gel, purified, and subjected to Sanger DNA sequencing for further analysis. Unfortunately, a laboratory technician made an error when setting up the Sanger sequencing reaction. Consequently, the sequencing reaction terminated at the first guanine (G) position, and no sequence data was obtained beyond the eighth nucleotide. The erroneous sequencing results are shown in the chromatogram in Figure 2.

Figure 2. Sanger sequencing chromatogram generated for the APC PCR amplicon.