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Mitosis is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis is an equational division which gives rise to genetically identical cells in which the total number of chromosomes is maintained. Mitosis is preceded by the S phase of interphase and is followed by telophase and cytokinesis; which divides the cytoplasm, organelles and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components. The different stages of mitosis altogether define the mitotic phase of a cell cycle—the division of the mother cell into two daughter cells genetically identical to each other.
Cell division is the process by which a parent cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukaryotes, there are two distinct types of cell division: a vegetative division (mitosis), producing daughter cells genetically identical to the parent cell, and a cell division that produces haploid gametes for sexual reproduction (meiosis), reducing the number of chromosomes from two of each type in the diploid parent cell to one of each type in the daughter cells. In Mitosis is a part of the cell cycle, in which, replicated chromosomes are separated into two new nuclei. Cell division gives rise to genetically identical cells in which the total number of chromosomes is maintained. In general, mitosis is preceded by the S stage of interphase and is followed by telophase and cytokinesis; which divides the cytoplasm, organelles, and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components. The different stages of mitosis all together define the M phase of an animal cell cycle—the division of the mother cell into two genetically identical daughter cells. To ensure proper progression through the cell cycle, DNA damage is detected and repaired at various checkpoints throughout the cycle. These checkpoints can halt progression through the cell cycle by inhibiting certain cyclin-CDK complexes. Meiosis undergoes two divisions resulting in four haploid daughter cells. Homologous chromosomes are separated in the first division of meiosis, such that each daughter cell has one copy of each chromosome. These chromosomes have already been replicated and have two sister chromatids which are then separated during the second division of meiosis. Both of these cell division cycles are used in the process of sexual reproduction at some point in their life cycle. Both are believed to be present in the last eukaryotic common ancestor.
In cell biology, the spindle apparatus is the cytoskeletal structure of eukaryotic cells that forms during cell division to separate sister chromatids between daughter cells. It is referred to as the mitotic spindle during mitosis, a process that produces genetically identical daughter cells, or the meiotic spindle during meiosis, a process that produces gametes with half the number of chromosomes of the parent cell.
Telophase is the final stage in both meiosis and mitosis in a eukaryotic cell. During telophase, the effects of prophase and prometaphase are reversed. As chromosomes reach the cell poles, a nuclear envelope is re-assembled around each set of chromatids, the nucleoli reappear, and chromosomes begin to decondense back into the expanded chromatin that is present during interphase. The mitotic spindle is disassembled and remaining spindle microtubules are depolymerized. Telophase accounts for approximately 2% of the cell cycle's duration.
Clathrin is a protein that plays a major role in the formation of coated vesicles. Clathrin was first isolated by Barbara Pearse in 1976. It forms a triskelion shape composed of three clathrin heavy chains and three light chains. When the triskelia interact they form a polyhedral lattice that surrounds the vesicle. The protein's name refers to this lattice structure, deriving from Latin clathri meaning lattice. Barbara Pearse named the protein clathrin at the suggestion of Graeme Mitchison, selecting it from three possible options. Coat-proteins, like clathrin, are used to build small vesicles in order to transport molecules within cells. The endocytosis and exocytosis of vesicles allows cells to communicate, to transfer nutrients, to import signaling receptors, to mediate an immune response after sampling the extracellular world, and to clean up the cell debris left by tissue inflammation. The endocytic pathway can be hijacked by viruses and other pathogens in order to gain entry to the cell during infection.
The spindle checkpoint, also known as the metaphase-to-anaphase transition, the spindle assembly checkpoint (SAC), the metaphase checkpoint, or the mitotic checkpoint, is a cell cycle checkpoint during metaphase of mitosis or meiosis that prevents the separation of the duplicated chromosomes (anaphase) until each chromosome is properly attached to the spindle. To achieve proper segregation, the two kinetochores on the sister chromatids must be attached to opposite spindle poles. Only this pattern of attachment will ensure that each daughter cell receives one copy of the chromosome. The defining biochemical feature of this checkpoint is the stimulation of the anaphase-promoting complex by M-phase cyclin-CDK complexes, which in turn causes the proteolytic destruction of cyclins and proteins that hold the sister chromatids together.
A kinetochore is a disc-shaped protein structure associated with duplicated chromatids in eukaryotic cells where the spindle fibers attach during cell division to pull sister chromatids apart. The kinetochore assembles on the centromere and links the chromosome to microtubule polymers from the mitotic spindle during mitosis and meiosis. The term kinetochore was first used in a footnote in a 1934 Cytology book by Lester W. Sharp and commonly accepted in 1936. Sharp's footnote reads: "The convenient term kinetochore has been suggested to the author by J. A. Moore", likely referring to John Alexander Moore who had joined Columbia University as a freshman in 1932.
Aurora kinases are serine/threonine kinases that are essential for cell proliferation. They are phosphotransferase enzymes that help the dividing cell dispense its genetic materials to its daughter cells. More specifically, Aurora kinases play a crucial role in cellular division by controlling chromatid segregation. Defects in this segregation can cause genetic instability, a condition which is highly associated with tumorigenesis. The first aurora kinases were identified in Drosophila melanogaster, where mutations led to failure of centrosome separation with the monopolar spindles reminiscent of the North Pole, suggesting the name aurora.
Aurora kinase inhibitors are a putative drug class for treating cancer. The Aurora kinase enzymes could be potential targets for novel small-molecule enzyme inhibitors.
David Moore Glover is a British geneticist and Research Professor of Biology and Biological Engineering at the California Institute of Technology. He served as Balfour Professor of Genetics at the University of Cambridge, a Wellcome Trust investigator in the Department of Genetics at the University of Cambridge, and Fellow of Fitzwilliam College, Cambridge. He serves as the first editor-in-chief of the open-access journal Open Biology published by the Royal Society.
Mitotic checkpoint serine/threonine-protein kinase BUB1 also known as BUB1 is an enzyme that in humans is encoded by the BUB1 gene.
Mitotic checkpoint serine/threonine-protein kinase BUB1 beta is an enzyme that in humans is encoded by the BUB1B gene. Also known as BubR1, this protein is recognized for its mitotic roles in the spindle assembly checkpoint (SAC) and kinetochore-microtubule interactions that facilitate chromosome migration and alignment. BubR1 promotes mitotic fidelity and protects against aneuploidy by ensuring proper chromosome segregation between daughter cells. BubR1 is proposed to prevent tumorigenesis.
Dynactin is a 23 subunit protein complex that acts as a co-factor for the microtubule motor cytoplasmic dynein-1. It is built around a short filament of actin related protein-1 (Arp1).
Targeting protein for Xklp2 is a protein that in humans is encoded by the TPX2 gene. It is one of the many spindle assembly factors that play a key role in inducing microtubule assembly and growth during M phase.
Transforming acidic coiled-coil-containing protein 3 is a protein that in humans is encoded by the TACC3 gene.
Nuclear pore complex protein Nup133, or Nucleoporin Nup133, is a protein that in humans is encoded by the NUP133 gene.
Shinya Inoué was a Japanese American biophysicist and cell biologist, a member of the National Academy of Sciences. His research field was the visualization of dynamic processes within living cells using light microscopy.
Mitotic catastrophe has been defined as either a cellular mechanism to prevent potentially cancerous cells from proliferating or as a mode of cellular death that occurs following improper cell cycle progression or entrance. Mitotic catastrophe can be induced by prolonged activation of the spindle assembly checkpoint, errors in mitosis, or DNA damage and operates to prevent genomic instability. It is a mechanism that is being researched as a potential therapeutic target in cancers, and numerous approved therapeutics induce mitotic catastrophe.
Anthony Arie Hyman is a British scientist and director at the Max Planck Institute of Molecular Cell Biology and Genetics.
J. Richard McIntosh is a Distinguished Professor Emeritus in Molecular, Cellular, and Developmental Biology at the University of Colorado Boulder. McIntosh first graduated from Harvard with a BA in Physics in 1961, and again with a Ph.D. in Biophysics in 1968. He began his teaching career at Harvard but has spent most of his career at the University of Colorado Boulder. At the University of Colorado Boulder, McIntosh taught biology courses at both the undergraduate and graduate levels. Additionally, he created an undergraduate course in the biology of cancer towards the last several years of his teaching career. McIntosh's research career looks at a variety of things, including different parts of mitosis, microtubules, and motor proteins.
References
- 1 2 Erp, Pepijn van (2019). "'Wetenschapsjournalistiek is nog erger dan sportjournalistiek'" [Science journalism is worse than sports journalism]. Skepter.
- 1 2 Schneider, Leonid (2008). Die Bedeutung von TACC3, eines Proteins der mitotischen Spindel, für die zelluläre Proliferation und Viabilität / Role of the mitotic spindle associated protein TACC3 in cell proliferation and survival (PDF). Universität Düsseldorf.
- ↑ Grove, Jack (7 November 2019). "Are legal concerns stifling scientific debate?". Times Higher Education .
- ↑ "Leonid Schneider, un canardeur chez les chercheurs". Le Monde (in French). 2023-08-26. Retrieved 2024-01-08.
- ↑ Else, Holly; Van Noorden, Richard (25 March 2021). "The fight against fake-paper factories that churn out sham science". Nature. 591 (7851): 516–519. Bibcode:2021Natur.591..516E. doi: 10.1038/d41586-021-00733-5 . PMID 33758408.
- ↑ Maouche, Seraya (2017-01-07). "Entretien avec Leonid Schneider : l'intégrité scientifique et la justice allemande". Club de Mediapart (in French). Retrieved 2021-09-14.
- ↑ Trossero, Denis (2021-07-01). "Pr Raoult : plainte et enquêtes ouvertes". La Provence (in French). Retrieved 2021-09-14.
- ↑ Jeff, Kiger (2021-02-08). "Retired Mayo doctor sues blogger over lost job offer". Post-Bulletin . Retrieved 2021-09-14.
