Timings of DNA synthesis in the nucleoli of Allium cepa L
01 Feb 1990-Cell Biology International Reports (No longer published by Elsevier)-Vol. 14, Iss: 2, pp 173-177
TL;DR: The timing of nucleolar DNA synthesis in root tip cells of Allium cepa LAs has been studied in this article, where the authors found that nucleolar chromatin in this plant species replicates in two phases during S period, once in the early and again towards the end of S phase.
About: This article is published in Cell Biology International Reports.The article was published on 1990-02-01. It has received 4 citations till now. The article focuses on the topics: Nucleolar chromatin & Chromatin.
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TL;DR: This review addresses the problem of understanding nucleolar morphology in terms of nucleolar function by reviewing in situ-cytochemical results that have not led to a generally accepted view on the structure-function correlation for nucleoli.
138 citations
01 Jan 1993
TL;DR: Its visibility both in the light-and the electron microscope is due to the fact that the genes for ribosomal RNA are not only transcribed but also processed and complexed with ribosomes in nucleoli, rendering them morphologically different from the rest of the karyoplasm.
Abstract: Nucleoli were noted by biologists very early (Fontana, 1781) and a lot of data has been accumulated on the structure of nucleoli in the last decades. Due to the work of Perry (1962; Perry et al., 1961) it is known that the nucleolus is the site of ribosome biogenesis. Its visibility both in the light-and the electron microscope is due to the fact that the genes for ribosomal RNA are not only transcribed but also processed and complexed with ribosomal proteins in nucleoli, rendering them morphologically different from the rest of the karyoplasm.
8 citations
TL;DR: In okadaic acid treated HeLa cells, the chromosomes sometimes condense without being accompanied by nuclear envelope breakdown, which strongly speak for the localization of nucleolar chromatin (ribosomal cistrons) within the dense nucleolar component of the interphase nucleolus.
6 citations
TL;DR: The nucleolar chromatin is traced from early prophase to the metaphase stage, where in metaphase it is fully condensed and in mitotic chromosomes this chromatin remains surrounded by achromatic materials resembling the fibrillar centre.
4 citations
References
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TL;DR: A low-viscosity embedding medium based on ERL-4206 is recommended for use in electron microscopy and has a long pot life of several days and infiltrates readily because of its low viscosity.
12,930 citations
Journal Article•
333 citations
TL;DR: Chromosomes in G1, S, G2 and early prophase of Allium cepa root tip nuclei are oriented in the same position as telophase chromosomes, and telomere-centromere DNA is late replicating.
Abstract: Chromosomes in G1, S, G2 and early prophase of Allium cepa root tip nuclei are oriented in the same position as telophase chromosomes. The centromeric heteroehromatin is aggregated in a chromocenter at one side of the nucleus, the telomeres scattered at the opposite side. Telomeres appear to associate with other telomeres in interphase in a roughly two by two fashion. Telomere-centromere DNA is late replicating. These results support the conclusion that chromosomes in higher organisms frequently maintain their telophase orientation from the end of telophase, during interphase and well into the next prophase.
85 citations
TL;DR: Premeiotic associations appear to be resolved prior to meiotic pairing, and there is no indication that premeiotic centromere associations are involved in prezygotene alignment of homologous chromosomes.
Abstract: Centromeres at premeiotic interphase are clustered and situated in a small area of the nucleus opposite to the nuclear envelope associated heterochromatic masses. The centromeres may occur singly or they may associate to form a structure composed of 2 or more centromeres. Many centromere associations are nonhomologous. Interphase centromeres are not attached to the nuclear envelope. — At zygotene and pachytene centromeres are no longer clustered at one pole of the nucleus but rather are distributed throughout the nucleus. Premeiotic associations appear to be resolved prior to meiotic pairing. Only homologous centromere associations occur during zygotene and pachytene. There is no indication that premeiotic centromere associations are involved in prezygotene alignment of homologous chromosomes.
77 citations
58 citations