Fig. 7.

Secondary deletion via large loop mismatch repair. A tandem duplication forms via ectopic recombination or replication slippage. At some point prior to fixation in the population the duplication pairs with an unduplicated chromatid in meiosis or mitosis, invoking the action of the large loop mismatch repair system. Imprecise excision results in a modified duplicate with partially deleted sequence. Large loop mismatch repair requires that duplications are polymorphic, and would therefore produce secondary modification over short timescales, resulting in rapid modification of tandem duplicates.