Figure 3.

Diagrammatic representation of potential contraction/deletion pathways. (A) Strand-slippage during replication may be exacerbated by hairpins formed on the template strand. Repriming more 5′ on the template would lead to nascent strands with fewer repeats than the template strand. A subsequent round of replication would generate a contracted allele. (B) MMEJ-mediated repair of a DSB is initiated by end-resection to reveal MHs at either side of the break. Annealing of these MHs is followed by removal of non-homologous flaps, filling of any gaps, perhaps by Polθ or Polβ, and ligation by either ligase 3 (Lig3) or ligase 1 (Lig1).