A dinokaryon is a

eukaryotic The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

nucleus present in dinoflagellates in which the

chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...

s are fibrillar in appearance (i.e. with unmasked DNA fibrils) and are more or less continuously condensed. Oxyrrhis marina

The nuclear envelope does not break down during

mitosis Mitosis () is a part of the cell cycle in eukaryote, eukaryotic cells in which replicated chromosomes are separated into two new Cell nucleus, nuclei. Cell division by mitosis is an equational division which gives rise to genetically identic ...

, which is thus termed closed

, or "dinomitosis". The mitotic spindle is extranuclear. Histones are absent. However, recent EST sequencing has revealed the presence of histones in one of the closest relative to dinoflagellates, '' Perkinsus marinus'' and an early-branching dinoflagellate, '' Hematodinium'' sp. However, histone-like proteins of bacterial origins are found in the coding regions at periphery of the dinokaryon's chromosomes.

References

Dinoflagellate biology Cell nucleus {{dinoflagellate-stub