Higher-order chromatin structure. A proposed model for chromatin arranged in a helical array consisting of six nucleosomes per turn of helix. The DNA double helix (shown in red) is wound around each histone octamer (shown in blue). The actual structure in cells is likely more heterogeneous and dynamic than suggested by this model.

[Information from J. T. Finch and A. Klug, Proc. Natl. Acad. Sci. U. S. A. 73:1897–1901, 1976.]