Mammalian Nuclei (image) Florida State University Share Print E-Mail Caption In mammalian nuclei, replication takes place at punctate sites or foci. Early-replicating foci localize to the interior of the nucleus (green), while the periphery of the nucleus and nucleoli harbor late replicating foci (red). Cytogenetic studies suggest very stable organization of the DNA within these labeled sites, but the molecular boundaries separating differentially replicating segments have remained elusive. High-resolution, microarray-based replication timing profiles (translucent graphs) revealed the sizes and locations of early- and late-replicating chromosome segments and demonstrated that they are highly conserved within a cell type, but globally re-organized and consolidated into larger coordinately replicating segments during differentiation of embryonic stem cells. Credit Courtesy of Florida State University Department of Biological Sciences Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.