Super Coiling of DNA
The DNA double helix
wraps around a nucleosome.
Six nucleosomes form one turn of a solenoid. Loops of solenoid
coils are attached to a non-histone protein scaffold. At the
fourth structural level, the scaffold forms a spiral 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 with
distinctive size and morphology. The chromatin in any
single chromosome appears
to be a single, continuous DNA helix.
Figure © 2000 by
Griffiths et al. ; text © 2014 by Steven M. Carr