The ultrastructural localization of deoxyribonucleic acid (DNA) synthesis was studied by electron-microscope autoradiography in human transforming lymphocytes, embryonic lung fibroblasts, epithelial cells and normoblasts. Euchromatin was found to be active in DNA synthesis in all cell types studied, whereas heterochromatin was inactive. However, DNA synthesis was also prominent in the regions where heterochromatin was thought to be decondensing to form euchromatin. Analysis of sequential changes in nuclear morphology of the transforming lymphocyte suggested that there is decondensation of heterochromatin during the S-phase until none is left. In nuclei with no heterochromatin a prominent localization of DNA synthesis was at the nuclear membrane. This sequence of complete decondensation of heterochromatin also seemed likely for fibroblasts and epithelial cells. Normoblasts however showed no stage where the nucleus was wholly euchromatic and it is suggested that in this cell decondensation of heterochromatin for replication is localized and transient.
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JOURNAL ARTICLE| 01 May 1969
Nuclear Morphology and the Ultra-Structural Localization of Deoxyribonucleic Acid Synthesis during Interphase
GILLIAN R. MILNER
Department of Medicine, University of Cambridge England
Received: 06 Aug 1968
Online Issn: 1477-9137
Print Issn: 0021-9533
Copyright © 1969 The Company of Biologists Ltd.
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GILLIAN R. MILNER; Nuclear Morphology and the Ultra-Structural Localization of Deoxyribonucleic Acid Synthesis during Interphase. J Cell Sci 1 May 1969; 4 (3): 569–582. doi: https://doi.org/10.1242/jcs.4.3.569
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