The mesokaryote Gyrodinium cohnii lacks nucleosomes

The dinoflagellate Gyrodinium cohnii has a distinct nuclear membrane but apparently lacks histones associated with its chromatin. Approximately 13% of the nuclear DNA is rapidly digested by micrococcal nuclease to acid soluble fragments and not to nucleosomal sized fragments as in the typical eukaryote. Moreover in the electron microscope the chromatin of G. cohnii appears as a thin filament of 40-60 Å in width without regularly spaced nucleosomes. These observations support the view that the dinoflagellates exhibit characteristics of both prokaryotes and eukaryotes.