Chiral discotic columnar germs of nucleosome core particles

In concentrated solution and in the presence of high concentrations of mono valent cations, nucleosome core particles order into a discotic columnar me sophase. This phase is limited to finite-sized hexagonal germs that further divide into six coiled branches, following an iterative process. We show h ow the structure of the germs comes from the competition between hexagonal packing and chirality with a combination of dendritic facetting and double- twist configurations. Geometrical considerations lead us to suspect that th e chirality of the eukaryotic chromosomes may originate from the same compe tition.