Secondary & Tertiary chromosome coiling

    The DNA double helix is wrapped twice around a octamer core unit that comprises eight histone proteins. These nucleosomes are separated by a run of spacer DNA complexed with a single histone H1 unit. At the tertiary level [right], six nucleosomes form a spiral organized around their H1 histone spacers, to form a solenoid.

Figure © 2000 by Griffiths et al. ; text © 2008 by Steven M. Carr