Distribution of globin genes in chicken reticulocyte chromatin fractionated on urografin gradients.

Buoyant density centrifugation in Urografin solutions resolved French Pressure Cell-sheared, and micrococcal nuclease-digested avian reticulocyte chromatin into a broad profile of two peaks. Hybridization experiments using a globin cDNA probe suggested minimal fractionation of transcriptionally active and inactive components with chromatin sheared at 6000 psi, while no evidence was obtained for any fractionation with chromatin sheared at lower or higher pressures, or with chromatin digested to various extents with micrococcal nuclease, despite a considerable spread of chromatin material across gradients.