FIG. 3.

DNA polymerase slippage model for instability in mononucleotide runs. Following a transient dissociation of the primer and template strand during DNA replication, the strands can reanneal in misaligned configuration, resulting either in a displaced single-strand loop on the primer (upper) or the template (lower) strand. If the resulting mismatches are not corrected before the next round of replication, the mispaired loops will give rise to unit size insertions or deletions, depending on whether the unpaired loop was in the primer or the template, respectively.