DNA strand displacement. Animation of a double-stranded DNA (deoxyribonucleic acid) sequence having one of its strands displaced by a single strand. At the end of the double strand (green and blue) there is a single-stranded tail that acts as a 'toe-hold' region. This region includes a sequence that is complementary to a sequence in the single strand (red), allowing this strand to bind to the 'toe-hold' area. The reaction then progresses, displacing the previously attached strand (green) and creating a new double-stranded DNA molecule (red and blue). DNA strand displacement has been used in research into DNA computing and molecular programming, the technique being used to construct a variety of components, devices, and circuits.