[Electron microscopic demonstration of links between DNA filaments and fibrillar areas of nucleolar RNA in interphase nuclei of L 929 cells].

Electronic opacification by DAB, following ribonuclease digestion, allowed us to observe a network of DNA filaments which appeared in close relation with both intranucleolar clumps of DNA on one hand, and with the nucleolar fibrillar RNA structure on the other hand. It is inferred that the ribosomal genes may be located on these filaments of DNA.