Slipped Strand Mispairing - Self-acceleration

Self-acceleration

SSM events can result in either insertions or deletions. Insertions are thought to be self-accelerating: as repeats grow longer, the probability of subsequent mispairing events increases. Insertions can expand simple tandem repeats by one or more units. In long repeats, expansions may involve two or more units. For example, insertion of a single repeat unit in GAGAGA expands the sequence to GAGAGAGA, while insertion of two repeat units in ₆ would produce ₈. Genomic regions with a high proportion of repeated DNA sequences (tandem repeats, microsatellites) are prone to strand slippage during DNA replication.