we are studying a 5bp insertion and for this, we perform a PCR method followed by SDS-PAGE electrophoresis. The method has been validated and yet, this gel was given to me today. So far, I has been given gels having only a single band as the ones shown in lanes 3-4. This molecular weight corresponds to the wild type. Do you have any idea what the other could be? Could they be a heteroduplex?