Isolation of chromatin bearing nascent RNA from nuclei of sea urchin embryos

Sea urchin embryos were labeled with C¹⁴ thymidine and H³ Uridine, the nuclei isolated, and a chromatin preparation partially deproteinized in salt and detergent. After banding this preparation in a Cs₂SO₄ gradient, the nascent RNA is associated with a small fraction of the chromatin at a density lighter than the bulk chromatin.