- supercoil
- su·per·coil 'sü-pər-.kȯi(ə)l n a double helix (as of DNA) that has undergone additional twisting in the same direction as or in the opposite direction from the turns in the original helix called also superhelixsupercoil vb
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su·per·coil (sooґpər-koil) 1. a tertiary conformation characteristic of a DNA molecule with constrained ends, as a circular plasmid or closed loops of DNA in a chromosome; the molecule is over- or underwound, with the axis of the helix twisted upon itself. In negatively supercoiled DNA, the DNA axis twists in the direction opposite that of the normal helical turns, causing underwinding of the helix, while in positively supercoiled DNA, the DNA axis twists with the direction of the normal helical turns, causing overwinding. Supercoiling plays a role in a variety of processes, including replication, transcription, and recombination. Called also superhelix. 2. to form such a tertiary structure.(A), Positively supercoiled DNA; (B), relaxed circle; (C), negatively supercoiled DNA.
Medical dictionary. 2011.