Comparison of chimeras generated by PCR and those hypothetically generated during the PacBio library preparation. (a) PCR-generated chimeras are typically created when an aborted amplicon acts as a primer for a heterologous template. Subsequent chimeras are about the same length as the non-chimeric amplicon and contain the forward (for.) and reverse (rev.) primer sequence at each end of the amplicon. (b) PacBio-generated chimeras originate during the adaptor ligation step. The length of these chimeras is measured in multiples of non-chimeric amplicon length, and they contain multiple forward and reverse primer sequences (found at the beginning and end of each segment).