Slipped strand DNA structures.

Slipped strand DNA structures are formed when complementary strands comprising direct repeats pair in a misaligned, or slipped, fashion along the DNA helix axis. Although slipped strand DNA may form in almost any direct repeat, to date, these structures have only been detected in short DNA repeats, termed unstable DNA repeats, in which expansion is associated with many neurodegenerative diseases. This alternative DNA structure, or a similar slipped intermediate DNA that may form during DNA replication or repair, may be a causative factor in the instability of the DNA sequences that can form these structures.