Chromatin fibre differences between condensed and dispersed chromatin: a comparative ultrastructure study.

Cells of different types from different species were investigated to determine if there are significant variations between chromatin fibre measurements in electron micrographs of thin sections. A larger chromatin fibre of 20 plus nm is seen in both condensed chromatin and dispersed chromatin and contains an irregularly folded or coiled fibril of 2.1 to 3.7 nm. In all cell types the larger fibre of dispersed chromatin was significantly thicker than the larger fibre of condensed chromatin. Numerous significant differences were also found between chromatin measurements of the different species. The ultrastructural differences may help explain the functional differences already known to exist between dispersed and condensed chromatin.