Changes in chromatin structure during the mitotic cycle

Summary Optical density profiles of Feulgen-stained nuclei ofBryonia dioica at different stages of the mitotic cycle were determined. Nuclei in the G₂ phase have a greater fraction of dense chromatin than nuclei in G₁ phase. However, nuclei at the end of the S phase have dispersed chromatin of minimal density. Thus, chromatin density oscillates during the mitotic cycle of this species, consequently the progressive increase in density previously recorded throughout the intermitotic period of two other species (onion and mouse) cannot be a general rule.