Cholesteric organization of DNA in vivo and in vitro

In concentrated solutions DNA organizes spontaneously to form the "cholesteric" phase which is one type of liquid crystal. We have reproducibly obtained both continuous cholesteric phases and isolated cholesteric globules in equilibrium with the isotropic phase. A comparison is made between this in vitro cholesteric organization and dinoflagellate chromosomes which present the same organization in vivo. The observed defects are analyzed in the two cases. It appears that the cholesteric organization is due to self-assembly phenomena and that the shape of globules and chromosomes is due both to surface tensions and to the presence of defects.