Question

What are some examples of mesokaryotic organisms?

Answer 1

Mesokaryotes are organisms that fall between the nucleoid of prokaryotes and the nucleus of eukaryotes, and their nucleus lacks histone proteins, rather possessing a novel class of proteins known as viral nucleoproteins. The nucleus of these organisms is covered by a nuclear membrane.

Complete answer:
The terms 'meso' and 'karyon' denotes 'in between' and 'nucleus,' respectively. Because mesokaryotic cells have a coherent nucleus like eukaryotic cells yet divide through amitosis like prokaryotes, the cells are called mesokaryotes, implying that their nucleus resembles both eukaryotic and prokaryotic nuclei. When the rest of the cell segregates, the nucleus of a mesokaryotic cell multiplies, with one nucleus accompanying each cell portion.
Mesokaryotic organisms include dinoflagellates, marine algae (Gymnodium, Peridinium), protozoa (Noctiulea), and some planktons.
Dinoflagellate nuclei are constricted for the entire interphase instead of during mitosis, which is closed and characterized by an extranuclear mitotic spindle. This type of nucleus was formerly thought to be a bridge between the prokaryotic' nucleoid region and eukaryotes' tangible nuclei, and was named "mesokaryotic," but it is now regarded as derivative rather than primitive.

Additional information:
The nucleus of the mesokaryotes shows the presence of a nuclear membrane. The DNA is usually linear but without histone proteins. RNA and protein synthesis of mesokaryotes are similar to that of eukaryotes. Cell movement is aided by gliding and flagella. Cell division takes place by binary fission.

Note:
Dodge (1966) coined the word "mesokaryotic" to describe the nucleus of dinoflagellates, owing to its transitional qualities between the coiled DNA regions of prokaryotic bacteria and the coherent eukaryotic nucleus. Typical eukaryotic organelles, such as Golgi bodies, mitochondria, and chloroplasts, are found in this group.