scispace - formally typeset
Search or ask a question
Topic

Metaphase

About: Metaphase is a research topic. Over the lifetime, 6925 publications have been published within this topic receiving 291590 citations. The topic is also known as: GO:0007091 & mitotic metaphase/anaphase transition.


Papers
More filters
Journal ArticleDOI
TL;DR: The first evidence is obtained that merotelic kinetochore orientation occurs very frequently during early mitosis in mammalian tissue cells and that two different correction mechanisms are critical for accurate chromosome segregation in cells possessing bipolar spindles and unperturbed chromosomes.
Abstract: Merotelic kinetochore orientation is an error that occurs when a single kinetochore becomes attached to microtubules from two spindle poles rather than just to one pole. We obtained the first evidence that merotelic kinetochore orientation occurs very frequently during early mitosis in mammalian tissue cells and that two different correction mechanisms are critical for accurate chromosome segregation in cells possessing bipolar spindles and unperturbed chromosomes. Our data show that about 30% of prometaphase PtK1 cells possess one or more merotelically oriented kinetochores. This frequency is increased to over 90% in cells recovering from a nocodazole-induced mitotic block. A delay in establishing spindle bipolarity is responsible for the high frequency of merotelic orientations seen in cells recovering from nocodazole, but not in untreated cells. The frequency of anaphase cells with merotelically oriented lagging chromosomes is 1% in untreated cells and 18% in cells recovering from nocodazole. Prolonging metaphase by 2 hours reduced the frequency of anaphase cells with lagging chromosomes both for untreated and for nocodazole-treated cells. Surprisingly, anaphase lagging chromosomes represented a very small fraction of merotelic kinetochore orientations present in late metaphase. Our data indicate that two correction mechanisms operate to prevent chromosome missegregation due to merotelic kinetochore orientation. The first, a pre-anaphase correction mechanism increases the ratio of kinetochore microtubules attached to the correct versus incorrect pole and might eventually result in kinetochore reorientation before anaphase onset. The increase in microtubule ratio to opposite poles is the groundwork for a second mechanism, active in anaphase, that promotes the segregation of merotelically oriented chromosomes to the correct pole.

280 citations

Journal ArticleDOI
01 Mar 1985-Science
TL;DR: The locus for the alpha-chain T-cells receptor may participate in oncogene activation in T-cell tumors through translocations and inversions detectable in human T- cell leukemias and lymphomas.
Abstract: A human complementary DNA clone specific for the alpha-chain of the T-cell receptor and a panel of rodent X human somatic cell hybrids were used to map the alpha-chain gene to human chromosome 14 in a region proximal to the immunoglobulin heavy chain locus. Analysis by means of in situ hybridization of human metaphase chromosomes served to further localize the alpha-chain gene to region 14q11q12, which is consistently involved in translocations and inversions detectable in human T-cell leukemias and lymphomas. Thus, the locus for the alpha-chain T-cell receptor may participate in oncogene activation in T-cell tumors.

280 citations

Journal ArticleDOI
TL;DR: The tested predictions of the Rabl-model support small time-dependent changes of the nuclear space occupied by single chromosomes and of their relative positions in the interphase nucleus seem possible, while the territorial organization of interphase chromosomes and their arrangement in general is maintained during interphase.
Abstract: In 1885 Carl Rabl published his theory on the internal structure of the interphase nucleus We have tested two predictions of this theory in fibroblasts grown in vitro from a female Chinese hamster, namely (1) the Rabl-orientation of interphase chromosomes and (2) the stability of the chromosome arrangement established in telophase throughout the subsequent interphase Tests were carried out by premature chromosome condensation (PCC) and laser-UV-microirradiation of the interphase nucleus Rabl-orientation of chromosomes was observed in G1 PCCs and G2 PCCs The cell nucleus was microirradiated in G1 at one or two sites and pulse-labelled with 3H-thymidine for 2h Cells were processed for autoradiography either immediately thereafter or after an additional growth period of 10 to 60h Autoradiographs show unscheduled DNA synthesis (UDS) in the microirradiated nuclear part(s) The distribution of labelled chromatin was evaluated in autoradiographs from 1035 cells after microirradiation of a single nuclear site and from 253 cells after microirradiation of two sites After 30 to 60h postincubation the labelled regions still appeared coherent although the average size of the labelled nuclear area fr increased from 142% (0h) to 265% (60h) The relative distance dr, ie the distance between two microirradiated sites divided by the diameter of the whole nucleus, showed a slight decrease with increasing incubation time Nine metaphase figures were evaluated for UDS-label after microirradiation of the nuclear edge in G1 An average of 43 chromosomes per cell were labelled Several chromosomes showed joint labelling of both distal chromosome arms including the telomeres, while the centromeric region was free from label This label pattern is interpreted as the result of a V-shaped orientation of these particular chromosomes in the interphase nucleus with their telomeric regions close to each other at the nuclear edge Our data support the tested predictions of the Rabl-model Small time-dependent changes of the nuclear space occupied by single chromosomes and of their relative positions in the interphase nucleus seem possible, while the territorial organization of interphase chromosomes and their arrangement in general is maintained during interphase The present limitations of the methods used for this study are discussed

279 citations

Journal ArticleDOI
TL;DR: A method for improved visualization of radial chromatin loops in undisrupted mitotic chromosomes and a nonhistone protein residual scaffold isolated from nuclease-digested chromosomes under conditions of low salt protein extraction are presented.
Abstract: We have developed procedures for depositing intact mitotic chromosomes and isolated residual scaffolds on electron microscope grids at controlled and reproducible levels of compaction. The chromosomes were isolated using a recently developed aqueous method. Our study has addressed two different aspects of chromosome structure. First, we present a method for improved visualization of radial chromatin loops in undisrupted mitotic chromosomes. Second, we have visualized a nonhistone protein residual scaffold isolated from nuclease-digested chromosomes under conditions of low salt protein extraction. These scaffolds, which have an extremely simple protein composition, are the size of chromosomes, are fibrous in nature, and are found to retain differentiated regions that appear to derive from the kinetochores and the chromatid axis. When our standard preparation conditions were used, the scaffold appearance was found to be very reproducible. If the ionic conditions were varied, however, the scaffold appearance underwent dramatic changes. In the presence of millimolar concentrations of Mg++ or high concentrations of NaCl, the fibrous scaffold protein network was observed to undergo a lateral aggregation or assembly into a coarse meshlike structure. The alteration of scaffold structure was apparently reversible. This observation is consistent with a model in which the scaffolding network plays a dynamic role in chromosome condensation at mitosis.

278 citations

Journal ArticleDOI
TL;DR: Friend leukemia cells resistant to cadmium toxicity were selected and revealed that the resistant cells are nearly tetraploid and contain, on the average, three very small chromosomes that are absent from non-resistant Friend cells.
Abstract: Friend leukemia cells resistant to cadmium toxicity were selected. More than 70% of total cysteine incorporation in these cells was into the metal-binding protein, metallothionein. We used cDNA and genomic DNA clones containing the metallothionein-I gene to measure the concentration of its mRNA, the rate of gene transcription, and the number of genes. On a per cell basis, optimally induced, cadmium-resistant cells have a 14-fold more metallothionein-I mRNA, a 6-fold higher rate of metallothionein-I gene transcription, and 6-fold more metallothionein-I genes than do nonresistant cells. Metaphase spreads revealed that the resistant cells are nearly tetraploid and contain, on the average, three very small chromosomes that are absent from non-resistant Friend cells.

274 citations


Network Information
Related Topics (5)
Chromatin
50.7K papers, 2.7M citations
86% related
Histone
28.8K papers, 1.5M citations
82% related
Mutation
45.2K papers, 2.6M citations
80% related
Gene
211.7K papers, 10.3M citations
80% related
Endoplasmic reticulum
48.3K papers, 2.4M citations
80% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202373
2022116
202182
202087
2019113
201888