Structure of the chromosomal material in inactive nuclei of chicken red blood cells

Electron microscope sections have been cut of chicken red blood cell nuclei by a novel procedure that produces zones of material below 100 A in thickness. After fixing and staining, electron dense structures are observed that have dimensions closely correlating with those determined for nucleosomes. These structures appear as wedge-shaped or as circular objects with a diameter of approximately 90-100 A. Five to eight of these objects are arranged in a spiral around a central core giving rise to a 250-300 A structure which may represent a superbead or a cross section of a solenoidal fibre.