An approach to the organization of eukaryotic genomes at a macromolecular level.

DNAs from three mammals, two amphibians, two invertebrates and a unicellular eukaryote, enzymatically degraded to molecular weights in the 1×106 to 2×106 range, were analyzed in their sedimentation coefficients, and modal and mean buoyant density of their CsCl bands. These were further analyzed in terms of Gaussian curves; a more detailed analysis of these genomes was done using the combined Cs2SO4−Ag+, CsCl approach of Thiery et al. (1976). The major components of degraded mammalian DNAs were identical, in both buoyant densities and relative amounts, to those of the undergraded preparations, with only slight density shifts for some components. In contrast, the major components of degraded amphibian DNAs showed a very different pattern compared to the undergraded DNAs; changes in buoyant densities and amounts of some components, the disappearance of some components and the appearance of the components were observed. Finally, the degraded Drosophila and Saccharomyces cerevisiae DNAs were similar to the undergraded preparations in that no components could be resolved within the main bands. Mouse DNA preparations ranging in molecular weight from 1·8×106 to over 200×106 were examined. Only very slight changes in the relative amounts of some components seemed to take place in the 1·8×106 to 66×106 molecular weight range: the buoyant densities of the components did not appear to vary in the size range, 1·8×106 to over 200×106.