The observation by electron microscopists that chromatin appeared similar to beads on a string provided an early clue that nucleosomes exist (Olins and Olins, 1974; Woodcock et al., 1976).

In an attempt to gain further insight into the dynamic processes of the in vitro nucleosome reconstitution, the linker histones-depleted oligo-nucleosomes were prepared from chicken erythrocytes.

However, the DNA is contained within the nucleus, which is only around 6 μm in diameter, due to compaction by packaging it as chromatin. Chromatin consists of nucleosomes, the basic structural unit of ...