Super Coiling of DNA: A summary

    The DNA double helix (red) wraps around a Nucleosome. Six nucleosomes form one turn of a Solenoid. Loops of solenoid coils are attached to a non-histone protein Scaffold. The scaffold is coiled, and is in turn coiled as a supercoil that constitutes a single chromatin fiber. During metaphase of the cell cycle, the chromatin condenses in an orderly manner to form a microscopically-visible chromosome (comprising two identical chromatids joined at a centromere) with distinctive size and morphology. The chromatin in any single chromosome appears to be a single, continuous DNA helix

    Super-coiling of DNA resembles the coiling of an unfastened rope for throwing, as in the following series showing the coiling of a rope as a maximally-compact, repetitive, organized "Bird's Nest or Daisy Chain" structure. Note that in the final photo, casting the loose bight at bottom allows the coiled rope to pay out smoothly, just as the DNA molecule unwinds without tangling.

Daisey Chain 1Daisy Chain 2Daisy Chain 3Daisy Chain 4

Top figure © 2000 by Griffiths et al.; "Bird's Nest" figures ©2013 by bcworkz; text © 2014 by Steven M. Carr