Figure 1.

Structure of the nucleolus. (A) Live-cell laser-scanning confocal microscope image showing the localization of a fluorescently tagged nucleolar marker protein (red) with a fluorescently tagged cytoplasmic marker protein (green). The nucleolus constitutes a significant proportion of the nucleus and contains defined features. (B) Diagrammatic representation of the mammalian nucleolus showing the positions of the FC, DFC and GC. (C) Scanning electron micrograph of a nucleolus purified from HeLa cells. The surface corresponds to a shell of highly condensed heterochromatin that surrounds the nucleolus in vivo (image courtesy of Angus Lamond, University of Dundee, UK). DFC, dense fibrillar component; FC, fibrillar centre; GC, granular component.