Dinoflagellate chromosomes

Nucleic acids. The DNA of the Dinoflagellate chromosomes forms a cholesteric network which is very similar to that often observed in the bacterial nucleus (6,9,18). Similar structures have been observed in mitochondrial DNA in certain Trypanosomes, after a treatment with certain drugs (review in. DNA in concentrated aqueous solutions can form cholesteric mesophases (4,18, 24). Remarkable cholesteric spherulites have been observed in concentrated ribosomal RNA (first considered as t-RNA, 33-35). ... 

Figure 6. Dinoflagellate chromosome (Prorocentmm micans), section plane parallel to the twist axis (courtesy of F. Lwolant.)...

Figure 7. Dinoflagellate chromosome (Trorocentnim micans), oblique sections. Arrows indicate the coiled bundles, (courtesy of F. Livolant).

The left-handedness of the mutual twist of DNA in chromosomes has been demonstrated by stereo electron microscopy of dinoflagellate chromosomes (9). 

Mitosis can now be viewed in the perspective of other chromosome motion and distribution mechanisms. The discussion here centers on the most striking contrasts afforded by recent studies of bacteria and dinoflagellates. As first argued in detail by Jacob et al. (1963) and as diagrammed in Figure 19, chromosome motion and distribution in such bacteria as Escherichia coli and Bacillus subtilis may depend upon chromosome attachment to the cell membrane (Fig. 19A), subsequent attachment of one... 

Fig. 20. Electron micrograph of a late division stage in the dinoflagellate Gyrodinium cohnii showing a portion of the nucleus with one channel lined by the nuclear envelope and filled with microtubules. Two chromosomes are labeled chm/ and the association of a third chromosome and the channel membrane is indicated by an arrow. X47,500. (From Kubai and Ris. 1969. /. Ce//5/o/., 40 508-528.)...

Electron microscope observations reveal that all dinoflagellates have common characteristics a vesicular cell covering, a two- to three-membrane chloroplast envelope, a persistent nuclear envelope with chromosomes attached to the envelope, and at some time in their life cycle, two dissimilar flagella (Taylor 1979 Steidinger 1983). In spite of the presence of flagella, the organisms are usually planktonic, and benthic in habit. 

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