Process in which chromosomes are replicated and separated into two new identical nuclei
For the type of cell division in sexually reproducing organisms used to produce gametes, see Meiosis. For excessive constriction of the pupils, see Miosis. For the parasitic infestation, see Myiasis. For muscle inflammation, see Myositis.
Mitosis (/maɪˈtoʊsɪs/) 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.[1] Mitosis is preceded by the S phase of interphase (during which DNA replication occurs) and is followed by telophase and cytokinesis, which divide the cytoplasm, organelles, and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components.[2] The different stages of mitosis altogether define the mitotic phase (M phase) of a cell cycle—the division of the mother cell into two daughter cells genetically identical to each other.[3]
The process of mitosis is divided into stages corresponding to the completion of one set of activities and the start of the next. These stages are preprophase (specific to plant cells), prophase, prometaphase, metaphase, anaphase, and telophase. During mitosis, the chromosomes, which have already duplicated during interphase, condense and attach to spindle fibers that pull one copy of each chromosome to opposite sides of the cell.[4] The result is two genetically identical daughter nuclei. The rest of the cell may then continue to divide by cytokinesis to produce two daughter cells.[5] The different phases of mitosis can be visualized in real time, using live cell imaging.[6]
An error in mitosis can result in the production of three or more daughter cells instead of the normal two. This is called tripolar mitosis and multipolar mitosis, respectively. These errors can be the cause of non-viable embryos that fail to implant.[7] Other errors during mitosis can induce mitotic catastrophe, apoptosis (programmed cell death) or cause mutations. Certain types of cancers can arise from such mutations.[8]
Mitosis occurs only in eukaryotic cells and varies between organisms.[9] For example, animal cells generally undergo an open mitosis, where the nuclear envelope breaks down before the chromosomes separate, whereas fungal cells generally undergo a closed mitosis, where chromosomes divide within an intact cell nucleus.[10][11] Most animal cells undergo a shape change, known as mitotic cell rounding, to adopt a near spherical morphology at the start of mitosis. Most human cells are produced by mitotic cell division. Important exceptions include the gametes – sperm and egg cells – which are produced by meiosis. Prokaryotes, bacteria and archaea which lack a true nucleus, divide by a different process called binary fission.[12]
Discovery
Numerous descriptions of cell division were made during 18th and 19th centuries, with various degrees of accuracy.[13] In 1835, the German botanist Hugo von Mohl, described cell division in the green algaeCladophora glomerata, stating that multiplication of cells occurs through cell division.[14][15][16] In 1838, Matthias Jakob Schleiden affirmed that "formation of new cells in their interior was a general rule for cell multiplication in plants", a view later rejected in favour of Mohl's model, due to contributions of Robert Remak and others.[17]
In animal cells, cell division with mitosis was discovered in frog, rabbit, and cat cornea cells in 1873 and described for the first time by the Polish histologistWacław Mayzel in 1875.[18][19]
Bütschli, Schneider and Fol might have also claimed the discovery of the process presently known as "mitosis".[13] In 1873, the German zoologist Otto Bütschli published data from observations on nematodes. A few years later, he discovered and described mitosis based on those observations.[20][21][22]
The term "mitosis", coined by Walther Flemming in 1882,[23] is derived from the Greek word μίτος (mitos, "warp thread").[24][25] There are some alternative names for the process,[26] e.g., "karyokinesis" (nuclear division), a term introduced by Schleicher in 1878,[27][28] or "equational division", proposed by August Weismann in 1887.[29] However, the term "mitosis" is also used in a broad sense by some authors to refer to karyokinesis and cytokinesis together.[30] Presently, "equational division" is more commonly used to refer to meiosis II, the part of meiosis most like mitosis.[31]
The primary result of mitosis and cytokinesis is the transfer of a parent cell's genome into two daughter cells. The genome is composed of a number of chromosomes—complexes of tightly coiled DNA that contain genetic information vital for proper cell function.[32] Because each resultant daughter cell should be genetically identical to the parent cell, the parent cell must make a copy of each chromosome before mitosis. This occurs during the S phase of interphase.[33]Chromosome duplication results in two identical sister chromatids bound together by cohesin proteins at the centromere.
When mitosis begins, the chromosomes condense and become visible. In some eukaryotes, for example animals, the nuclear envelope, which segregates the DNA from the cytoplasm, disintegrates into small vesicles. The nucleolus, which makes ribosomes in the cell, also disappears. Microtubules project from opposite ends of the cell, attach to the centromeres, and align the chromosomes centrally within the cell. The microtubules then contract to pull the sister chromatids of each chromosome apart.[34] Sister chromatids at this point are called daughter chromosomes. As the cell elongates, corresponding daughter chromosomes are pulled toward opposite ends of the cell and condense maximally in late anaphase. A new nuclear envelope forms around each set of daughter chromosomes, which decondense to form interphase nuclei.
During mitotic progression, typically after the anaphase onset, the cell may undergo cytokinesis. In animal cells, a cell membrane pinches inward between the two developing nuclei to produce two new cells. In plant cells, a cell plate forms between the two nuclei. Cytokinesis does not always occur; coenocytic (a type of multinucleate condition) cells undergo mitosis without cytokinesis.
Diagram of interphase and the following five mitotic stages of the M phase that includes cytokinesis.
The interphase is a much longer phase of the cell cycle than the relatively short M phase. During interphase the cell prepares itself for the process of cell division. Interphase is divided into three subphases: G1 (first gap), S (synthesis), and G2 (second gap). During all three parts of interphase, the cell grows by producing proteins and cytoplasmic organelles. However, chromosomes are replicated only during the S phase. Thus, a cell grows (G1), continues to grow as it duplicates its chromosomes (S), grows more and prepares for mitosis (G2), and finally divides (M) before restarting the cycle.[33] All these phases in the cell cycle are highly regulated by cyclins, cyclin-dependent kinases, and other cell cycle proteins. The phases follow one another in strict order and there are cell cycle checkpoints that give the cell cues to proceed or not, from one phase to another.[35] Cells may also temporarily or permanently leave the cell cycle and enter G0 phase to stop dividing. This can occur when cells become overcrowded (density-dependent inhibition) or when they differentiate to carry out specific functions for the organism, as is the case for human heart muscle cells and neurons. Some G0 cells have the ability to re-enter the cell cycle.
DNA double-strand breaks can be repaired during interphase by two principal processes.[36] The first process, non-homologous end joining (NHEJ), can join the two broken ends of DNA in the G1, S and G2 phases of interphase. The second process, homologous recombinational repair (HRR), is more accurate than NHEJ in repairing double-strand breaks. HRR is active during the S and G2 phases of interphase when DNA replication is either partially accomplished or after it is completed, since HRR requires two adjacent homologs.
Interphase helps prepare the cell for mitotic division. It dictates whether the mitotic cell division will occur. It carefully stops the cell from proceeding whenever the cell's DNA is damaged or has not completed an important phase. The interphase is very important as it will determine if mitosis completes successfully. It will reduce the amount of damaged cells produced and the production of cancerous cells. A miscalculation by the key Interphase proteins could be crucial as the latter could potentially create cancerous cells.[37]
In plant cells only, prophase is preceded by a preprophase stage. In highly vacuolated plant cells, the nucleus has to migrate into the center of the cell before mitosis can begin. This is achieved through the formation of a phragmosome, a transverse sheet of cytoplasm that bisects the cell along the future plane of cell division. In addition to phragmosome formation, preprophase is characterized by the formation of a ring of microtubules and actin filaments (called preprophase band) underneath the plasma membrane around the equatorial plane of the future mitotic spindle. This band marks the position where the cell will eventually divide. The cells of higher plants (such as the flowering plants) lack centrioles; instead, microtubules form a spindle on the surface of the nucleus and are then organized into a spindle by the chromosomes themselves, after the nuclear envelope breaks down.[38] The preprophase band disappears during nuclear envelope breakdown and spindle formation in prometaphase.[39]: 58–67
During prophase, which occurs after G2 interphase, the cell prepares to divide by tightly condensing its chromosomes and initiating mitotic spindle formation. During interphase, the genetic material in the nucleus consists of loosely packed chromatin. At the onset of prophase, chromatin fibers condense into discrete chromosomes that are typically visible at high magnification through a light microscope. In this stage, chromosomes are long, thin, and thread-like. Each chromosome has two chromatids. The two chromatids are joined at the centromere.
Close to the nucleus of an animal cell are structures called centrosomes, consisting of a pair of centrioles surrounded by a loose collection of proteins. The centrosome is the coordinating center for the cell's microtubules. A cell inherits a single centrosome at cell division, which is duplicated by the cell before a new round of mitosis begins, giving a pair of centrosomes. The two centrosomes polymerize tubulin to help form a microtubule spindle apparatus. Motor proteins then push the centrosomes along these microtubules to opposite sides of the cell. Although centrosomes help organize microtubule assembly, they are not essential for the formation of the spindle apparatus, since they are absent from plants,[38] and are not absolutely required for animal cell mitosis.[44]
At the beginning of prometaphase in animal cells, phosphorylation of nuclear lamins causes the nuclear envelope to disintegrate into small membrane vesicles. As this happens, microtubules invade the nuclear space. This is called open mitosis, and it occurs in some multicellular organisms. Fungi and some protists, such as algae or trichomonads, undergo a variation called closed mitosis where the spindle forms inside the nucleus, or the microtubules penetrate the intact nuclear envelope.[45][46]
In late prometaphase, kinetochore microtubules begin to search for and attach to chromosomal kinetochores.[47] A kinetochore is a proteinaceous microtubule-binding structure that forms on the chromosomal centromere during late prophase.[47][48] A number of polar microtubules find and interact with corresponding polar microtubules from the opposite centrosome to form the mitotic spindle.[49] Although the kinetochore structure and function are not fully understood, it is known that it contains some form of molecular motor.[50] When a microtubule connects with the kinetochore, the motor activates, using energy from ATP to "crawl" up the tube toward the originating centrosome. This motor activity, coupled with polymerisation and depolymerisation of microtubules, provides the pulling force necessary to later separate the chromosome's two chromatids.[50]
After the microtubules have located and attached to the kinetochores in prometaphase, the two centrosomes begin pulling the chromosomes towards opposite ends of the cell. The resulting tension causes the chromosomes to align along the metaphase plate at the equatorial plane, an imaginary line that is centrally located between the two centrosomes (at approximately the midline of the cell).[49] To ensure equitable distribution of chromosomes at the end of mitosis, the metaphase checkpoint guarantees that kinetochores are properly attached to the mitotic spindle and that the chromosomes are aligned along the metaphase plate.[51] If the cell successfully passes through the metaphase checkpoint, it proceeds to anaphase.
During anaphase A, the cohesins that bind sister chromatids together are cleaved, forming two identical daughter chromosomes.[52] Shortening of the kinetochore microtubules pulls the newly formed daughter chromosomes to opposite ends of the cell. During anaphase B, polar microtubules push against each other, causing the cell to elongate.[53] In late anaphase, chromosomes also reach their overall maximal condensation level, to help chromosome segregation and the re-formation of the nucleus.[54] In most animal cells, anaphase A precedes anaphase B, but some vertebrate egg cells demonstrate the opposite order of events.[52]
Telophase (from the Greek word τελος meaning "end") is a reversal of prophase and prometaphase events. At telophase, the polar microtubules continue to lengthen, elongating the cell even more. If the nuclear envelope has broken down, a new nuclear envelope forms using the membrane vesicles of the parent cell's old nuclear envelope. The new envelope forms around each set of separated daughter chromosomes (though the membrane does not enclose the centrosomes) and the nucleolus reappears. Both sets of chromosomes, now surrounded by new nuclear membrane, begin to "relax" or decondense. Mitosis is complete. Each daughter nucleus has an identical set of chromosomes. Cell division may or may not occur at this time depending on the organism.
Cytokinesis is not a phase of mitosis, but rather a separate process necessary for completing cell division. In animal cells, a cleavage furrow (pinch) containing a contractile ring, develops where the metaphase plate used to be, pinching off the separated nuclei.[55] In both animal and plant cells, cell division is also driven by vesicles derived from the Golgi apparatus, which move along microtubules to the middle of the cell.[56] In plants, this structure coalesces into a cell plate at the center of the phragmoplast and develops into a cell wall, separating the two nuclei. The phragmoplast is a microtubule structure typical for higher plants, whereas some green algae use a phycoplast microtubule array during cytokinesis.[39]: 64–7, 328–9 Each daughter cell has a complete copy of the genome of its parent cell. The end of cytokinesis marks the end of the M-phase.
There are many cells where mitosis and cytokinesis occur separately, forming single cells with multiple nuclei. The most notable occurrence of this is among the fungi, slime molds, and coenocytic algae, but the phenomenon is found in various other organisms. Even in animals, cytokinesis and mitosis may occur independently, for instance during certain stages of fruit fly embryonic development.[57]
Function
The function or significance of mitosis, is the maintenance of the chromosomal set; each formed cell receives chromosomes that are alike in composition and equal in number to the chromosomes of the parent cell.
Mitosis occurs in the following circumstances:
Development and growth: The number of cells within an organism increases by mitosis. This is the basis of the development of a multicellular body from a single cell, i.e., zygote and also the basis of the growth of a multicellular body.
Cell replacement: In some parts of the body, e.g. skin and digestive tract, cells are constantly sloughed off and replaced by new ones.[58] New cells are formed by mitosis and so are exact copies of the cells being replaced. In like manner, red blood cells have a short lifespan (only about 3 months) and new RBCs are formed by mitosis.[59]
Regeneration: Some organisms can regenerate body parts. The production of new cells in such instances is achieved by mitosis. For example, starfish regenerate lost arms through mitosis.
Asexual reproduction: Some organisms produce genetically similar offspring through asexual reproduction. For example, the hydra reproduces asexually by budding. The cells at the surface of hydra undergo mitosis and form a mass called a bud. Mitosis continues in the cells of the bud and this grows into a new individual. The same division happens during asexual reproduction or vegetative propagation in plants.
Variations
Forms of mitosis
The mitosis process in the cells of eukaryotic organisms follows a similar pattern, but with variations in three main details. "Closed" and "open" mitosis can be distinguished on the basis of nuclear envelope remaining intact or breaking down. An intermediate form with partial degradation of the nuclear envelope is called "semiopen" mitosis. With respect to the symmetry of the spindle apparatus during metaphase, an approximately axially symmetric (centered) shape is called "orthomitosis", distinguished from the eccentric spindles of "pleuromitosis", in which mitotic apparatus has bilateral symmetry. Finally, a third criterion is the location of the central spindle in case of closed pleuromitosis: "extranuclear" (spindle located in the cytoplasm) or "intranuclear" (in the nucleus).[9]
closed intranuclear pleuromitosis
closed extranuclear pleuromitosis
closed orthomitosis
semiopen pleuromitosis
semiopen orthomitosis
open orthomitosis
Nuclear division takes place only in cells of organisms of the eukaryotic domain, as bacteria and archaea have no nucleus. Bacteria and archaea undergo a different type of division.[60][61] Within each of the eukaryotic supergroups, mitosis of the open form can be found, as well as closed mitosis, except for unicellular Excavata, which show exclusively closed mitosis.[62] Following, the occurrence of the forms of mitosis in eukaryotes:[9][63]
Semiopen pleuromitosis is typical of most Apicomplexa.
Semiopen orthomitosis occurs with different variants in some amoebae (Lobosa) and some green flagellates (e.g., Raphidophyta or Volvox).
Open orthomitosis is typical in mammals and other Metazoa, and in land plants; but it also occurs in some protists.
Errors and other variations
Errors can occur during mitosis, especially during early embryonic development in humans.[64] During each step of mitosis, there are normally checkpoints as well that control the normal outcome of mitosis.[65] But, occasionally to almost rarely, mistakes will happen. Mitotic errors can create aneuploid cells that have too few or too many of one or more chromosomes, a condition associated with cancer.[66][67] Early human embryos, cancer cells, infected or intoxicated cells can also suffer from pathological division into three or more daughter cells (tripolar or multipolar mitosis), resulting in severe errors in their chromosomal complements.[7]
In nondisjunction, sister chromatids fail to separate during anaphase.[68] One daughter cell receives both sister chromatids from the nondisjoining chromosome and the other cell receives none. As a result, the former cell gets three copies of the chromosome, a condition known as trisomy, and the latter will have only one copy, a condition known as monosomy. On occasion, when cells experience nondisjunction, they fail to complete cytokinesis and retain both nuclei in one cell, resulting in binucleated cells.[69]
Anaphase lag occurs when the movement of one chromatid is impeded during anaphase.[68] This may be caused by a failure of the mitotic spindle to properly attach to the chromosome. The lagging chromatid is excluded from both nuclei and is lost. Therefore, one of the daughter cells will be monosomic for that chromosome.
Endoreduplication (or endoreplication) occurs when chromosomes duplicate but the cell does not subsequently divide. This results in polyploid cells or, if the chromosomes duplicates repeatedly, polytene chromosomes.[68][70] Endoreduplication is found in many species and appears to be a normal part of development.[70]Endomitosis is a variant of endoreduplication in which cells replicate their chromosomes during S phase and enter, but prematurely terminate, mitosis. Instead of being divided into two new daughter nuclei, the replicated chromosomes are retained within the original nucleus.[57][71] The cells then re-enter G1 and S phase and replicate their chromosomes again.[71] This may occur multiple times, increasing the chromosome number with each round of replication and endomitosis. Platelet-producing megakaryocytes go through endomitosis during cell differentiation.[72][73]
Amitosis in ciliates and in animal placental tissues results in a random distribution of parental alleles.
In histopathology, the mitosis rate (mitotic count or mitotic index) is an important parameter in various types of tissue samples, for diagnosis as well as to further specify the aggressiveness of tumors. For example, there is routinely a quantification of mitotic count in breast cancer classification.[74] The mitoses must be counted in an area of the highest mitotic activity. Visually identifying these areas, is difficult in tumors with very high mitotic activity.[75] Also, the detection of atypical forms of mitosis can be used both as a diagnostic and prognostic marker.[citation needed] For example, lag-type mitosis (non-attached condensed chromatin in the area of the mitotic figure) indicates high risk human papillomavirus infection-related Cervical cancer.[citation needed] In order to improve the reproducibility and accuracy of the mitotic count, automated image analysis using deep learning-based algorithms have been proposed.[76] However, further research is needed before those algorithms can be used to routine diagnostics.
Normal and atypical forms of mitosis in cancer cells. A, normal mitosis; B, chromatin bridge; C, multipolar mitosis; D, ring mitosis; E, dispersed mitosis; F, asymmetrical mitosis; G, lag-type mitosis; and H, micronuclei. H&E stain.
In animal tissue, most cells round up to a near-spherical shape during mitosis.[77][78][79] In epithelia and epidermis, an efficient rounding process is correlated with proper mitotic spindle alignment and subsequent correct positioning of daughter cells.[78][79][80][81] Moreover, researchers have found that if rounding is heavily suppressed it may result in spindle defects, primarily pole splitting and failure to efficiently capture chromosomes.[82] Therefore, mitotic cell rounding is thought to play a protective role in ensuring accurate mitosis.[81][83]
Rounding forces are driven by reorganization of F-actin and myosin (actomyosin) into a contractile homogeneous cell cortex that 1) rigidifies the cell periphery[83][84][85] and 2) facilitates generation of intracellular hydrostatic pressure (up to 10 fold higher than interphase).[86][87][88] The generation of intracellular pressure is particularly critical under confinement, such as would be important in a tissue scenario, where outward forces must be produced to round up against surrounding cells and/or the extracellular matrix. Generation of pressure is dependent on formin-mediated F-actin nucleation[88] and Rho kinase (ROCK)-mediated myosin II contraction,[84][86][88] both of which are governed upstream by signaling pathways RhoA and ECT2[84][85] through the activity of Cdk1.[88] Due to its importance in mitosis, the molecular components and dynamics of the mitotic actomyosin cortex is an area of active research.
Mitotic recombination
Mitotic cells irradiated with X-rays in the G1 phase of the cell cycle repair recombinogenic DNA damages primarily by recombination between homologous chromosomes.[89] Mitotic cells irradiated in the G2 phase repair such damages preferentially by sister-chromatid recombination.[89]Mutations in genes encoding enzymes employed in recombination cause cells to have increased sensitivity to being killed by a variety of DNA damaging agents.[90][91][92] These findings suggest that mitotic recombination is an adaptation for repairing DNA damages including those that are potentially lethal.
Evolution
There are prokaryotic homologs of all the key molecules of eukaryotic mitosis (e.g., actins, tubulins). Being a universal eukaryotic property, mitosis probably arose at the base of the eukaryotic tree. As mitosis is less complex than meiosis, meiosis may have arisen after mitosis.[93] However, sexual reproduction involving meiosis is also a primitive characteristic of eukaryotes.[94] Thus meiosis and mitosis may both have evolved, in parallel, from ancestral prokaryotic processes.
While in bacterial cell division, after duplication of DNA, two circular chromosomes are attached to a special region of the cell membrane, eukaryotic mitosis is usually characterized by the presence of many linear chromosomes, whose kinetochores attaches to the microtubules of the spindle. In relation to the forms of mitosis, closed intranuclear pleuromitosis seems to be the most primitive type, as it is more similar to bacterial division.[9]
Early prophase: Polar microtubules, shown as green strands, have established a matrix around the currently intact nucleus, with the condensing chromosomes in blue. The red nodules are the centromeres.
Early prometaphase: The nuclear membrane has just disassembled, allowing the microtubules to quickly interact with the kinetochores, which assemble on the centromeres of the condensing chromosomes.
Metaphase: The centrosomes have moved to the poles of the cell and have established the mitotic spindle. The chromosomes have congressed at the metaphase plate.
Anaphase: Kinetochore microtubules pull the two sets of chromosomes apart, and lengthening polar microtubules push the halves of the dividing cell further apart, while chromosomes are condensed maximally.
Telophase: Reversal of prophase and prometaphase events and thus completing the cell cycle.
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^ abcdRaikov IB (1994). "The diversity of forms of mitosis in protozoa: A comparative review". European Journal of Protistology. 30 (3): 253–69. doi:10.1016/S0932-4739(11)80072-6.
^ abRoss, Anna E. "Human Anatomy & Physiology I: A Chronology of the Description of Mitosis". Christian Brothers University. Retrieved 02 May 2018. linkArchived 2016-05-12 at the Wayback Machine.
^"Notes and memoranda: The late professor von Mohl". Quarterly Journal of Microscopical Science, v. XV, New Series, p. 178-181, 1875. link.
^Weyers, Wolfgang (2002). 150 Years of cell division. Dermatopathology: Practical & Conceptual, Vol. 8, No. 2. linkArchived 2019-04-02 at the Wayback Machine
^Iłowiecki M (1981). Dzieje nauki polskiej. Warszawa: Wydawnictwo Interpress. p. 187. ISBN978-83-223-1876-8.
^Bütschli, O. (1873). Beiträge zur Kenntnis der freilebenden Nematoden. Nova Acta der Kaiserlich Leopoldinisch-Carolinischen Deutschen Akademie der Naturforscher 36, 1-144. linkArchived 2018-08-11 at the Wayback Machine.
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^Battaglia E (1987). "Embryological questions: 12. Have the Polygonum and Allium types been rightly established?". Ann Bot. 45. Rome: 81–117. p. 85: Already in 1887, Weismann gave the names Aequationstheilung to the usual cell division, and Reduktionstheilungen to the two divisions involved in the halving process of the number of Kernsegmente
^Mauseth JD (1991). Botany: an Introduction to Plant Biology. Philadelphia: Saunders College Publishing. ISBN9780030302220. p. 102: Cell division is cytokinesis, and nuclear division is karyokinesis. The words "mitosis" and "meiosis" technically refer only to karyokinesis but are frequently used to describe cytokinesis as well.
^Prescott DM, Bender MA (March 1962). "Synthesis of RNA and protein during mitosis in mammalian tissue culture cells". Experimental Cell Research. 26 (2): 260–8. doi:10.1016/0014-4827(62)90176-3. PMID14488623.
^Olson MO (2011). The Nucleolus. Vol. 15 of Protein Reviews. Berlin: Springer Science & Business Media. p. 15. ISBN9781461405146.
^Heywood P (June 1978). "Ultrastructure of mitosis in the chloromonadophycean alga Vacuolaria virescens". Journal of Cell Science. 31: 37–51. doi:10.1242/jcs.31.1.37. PMID670329.
^Ribeiro KC, Pereira-Neves A, Benchimol M (June 2002). "The mitotic spindle and associated membranes in the closed mitosis of trichomonads". Biology of the Cell. 94 (3): 157–72. doi:10.1016/S0248-4900(02)01191-7. PMID12206655. S2CID29081466.
^ abChan GK, Liu ST, Yen TJ (November 2005). "Kinetochore structure and function". Trends in Cell Biology. 15 (11): 589–98. doi:10.1016/j.tcb.2005.09.010. PMID16214339.
^Cheeseman IM, Desai A (January 2008). "Molecular architecture of the kinetochore-microtubule interface". Nature Reviews. Molecular Cell Biology. 9 (1): 33–46. doi:10.1038/nrm2310. PMID18097444. S2CID34121605.
^Chan GK, Yen TJ (2003). "The mitotic checkpoint: a signaling pathway that allows a single unattached kinetochore to inhibit mitotic exit". Progress in Cell Cycle Research. 5: 431–9. PMID14593737.
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^ abcIourov IY, Vorsanova SG, Yurov YB (2006). "Chromosomal Variations in Mammalian Neuronal Cells: Known Facts and Attractive Hypotheses". In Jeon KJ (ed.). International Review Of Cytology: A Survey of Cell Biology. Vol. 249. Waltham, MA: Academic Press. p. 146. ISBN9780080463506.
^ abLancaster OM, Baum B (October 2014). "Shaping up to divide: coordinating actin and microtubule cytoskeletal remodelling during mitosis". Seminars in Cell & Developmental Biology. 34: 109–15. doi:10.1016/j.semcdb.2014.02.015. PMID24607328.
^Botthof JG, Bielczyk-Maczyńska E, Ferreira L, Cvejic A (May 2017). "rad51 leads to Fanconi anemia-like symptoms in zebrafish". Proceedings of the National Academy of Sciences of the United States of America. 114 (22): E4452–E4461. doi:10.1073/pnas.1620631114. PMC5465903. PMID28512217. Here we provide in vivo evidence that the decrease in HSPC numbers in adult fish indeed stems from a combination of decreased proliferation and increased apoptosis during embryonic development. This defect appears to be mediated via p53(10), as our p53/rad51 double mutants did not display any observable hematological defects in embryos or adults.
^Bernstein, H., Bernstein, C. Evolutionary origin and adaptive function of meiosis. In "Meiosis", Intech Publ (Carol Bernstein and Harris Bernstein editors), Chapter 3: 41-75 (2013).
Further reading
Morgan DL (2007). The cell cycle: principles of control. London: Published by New Science Press in association with Oxford University Press. ISBN978-0-9539181-2-6.
Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2002). "Mitosis". Molecular Biology of the Cell (4th ed.). Garland Science. Retrieved 2006-01-22.
Lodish H, Berk A, Zipursky L, Matsudaira P, Baltimore D, Darnell J (2000). "Overview of the Cell Cycle and Its Control". Molecular Cell Biology (4th ed.). W. H. Freeman. Retrieved 2006-01-22.
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OerzjoemУржум Plaats in Rusland Locatie in Rusland Kerngegevens Oblast Kirov Coördinaten 57° 7′ NB, 50° 0′ OL Algemeen Inwoners (oktober 2010) 10.213 Overig Netnummer(s) (+7) (+7) 83363 OKATO-code 33 241 501 Tijdzone SAMT (UTC+4) Portaal Rusland Oerzjoem (Russisch: Уржум) is een kleine stad in Rusland, gelegen in het oblast Kirov, 195 kilometer ten zuiden van de districtshoofdstad Kirov. Geschiedenis Oorspronkelijk bevonden zich op de plek van Oerzjoem ne...
Araña Ficha técnicaDirección Andrés WoodProducción Alejandra GarcíaGuion Guillermo Calderón Andrés WoodMúsica Antonio PintoFotografía M. I. Littin-MenzMontaje Andrea ChignoliProtagonistas Mercedes Morán María Valverde Marcelo Alonso Pedro Fontaine Felipe Armas Gabriel Urzúa Caio Blat María Gracia Omegna Mario Horton Ver todos los créditos (IMDb)Datos y cifrasPaís ChileArgentinaBrasilAño 2019Género Thriller políticoDuración 100 minutosIdioma(s) EspañolFicha en IMDbFicha en...
NSKK-Mann The ranks and insignia of the National Socialist Motor Corps (Nationalsozialistisches Kraftfahrkorps, abbr. NSKK) were a paramilitary rank system in Germany used between the years of 1931 and 1945. They were based closely on the ranks and insignia of the Sturmabteilung (SA), of which the NSKK was originally a part. Rank Insignia Collar insignia[1] Shoulder insignia NSKK Rank[2][3] Translation Heer equivalent[3] Korpsführer Corps Leader Generalfeldmar...
Bilateral relationsIsrael–United Arab Emirates relations Israel United Arab Emirates Diplomatic missionEmbassy of Israel, Abu DhabiEmbassy of United Arab Emirates, Tel AvivEnvoyIsraeli Ambassador to United Arab Emirates Eitan Na'ehEmirati Ambassador to Israel Mohamed Al Khaja Flags of Israel and the UAE, together with the flag of Netanya, flown on Netanya's Shalom Bridge over Highway 2. August 2020, Netanya, Israel. 4X-EHD, the El Al Boeing 737-900ER plane used in the historic first direct ...
Villa Metzler Villa Metzler, Schaumainkai 15, flankiert von Ginkgo (links) und Urweltmammutbaum (rechts) Daten Ort Frankfurt am Main, Hessen Baumeister Architektenfamilie Kayser oder Mack Baujahr 1802/04, Umbau 1863/65 Höhe ca. 16 m Grundfläche ca. 220 m² Koordinaten 50° 6′ 25″ N, 8° 40′ 54″ O50.1069444444448.6816666666667Koordinaten: 50° 6′ 25″ N, 8° 40′ 54″ O Besonderheiten Klassizistisches Geb...
1999 single by Robbie Williams It's Only UsSingle by Robbie Williamsfrom the album FIFA 2000: The Album and I've Been Expecting You (2002 re-release) A-sideShe's the OneReleased8 November 1999 (1999-11-08)[1]Length 2:50 (It's Only Us) 4:18 (She's the One) LabelChrysalisSongwriter(s) Robbie Williams Guy Chambers Producer(s) Guy Chambers Steve Power Robbie Williams singles chronology Strong (1999) She's the One / It's Only Us (1999) Win Some Lose Some (2000) Music videoIt...
Symphony by Krzysztof Penderecki Symphony No. 3by Krzysztof PendereckiThe composer in 2008OccasionCentenary of the Munich PhilharmonicComposed1988 (1988)–95Performed6 December 1995 (1995-12-06), MunichDuration50 min.Movements5Scoringorchestra The Symphony No. 3 is a symphony in five movements composed between 1988 and 1995 by Krzysztof Penderecki. It was commissioned and completed for the centenary of the Munich Philharmonic.[1] Its earliest version, Passacaglia ...
TroxyFormer namesTroxy Cinema, London Opera Centre, Top Rank Bingo, Mecca BingoAddress490 Commercial RoadLondon E1 0HXEnglandLocationStepneyOwnerAshburn Estates LtdOperatorAshburn Estates LtdTypeEarly 20th century art deco cinemaSeating typeFixed tiered seating and booths in the circleCapacity3,100ConstructionBuilt1932Opened11 September 1933Renovated2012-2013Construction cost£250 thousand(£75.1 million in 2021 pounds [1])ArchitectGeorge ColesWebsiteVenue Website Troxy is a Grad...
English vocalist and musician Martina Topley-BirdTopley-Bird performing with Massive Attack at Conegliano in 2009Background informationBirth nameMartina Gillian TopleyBorn (1975-05-07) 7 May 1975 (age 48)St Pancras, London, EnglandOriginBristol, EnglandGenresTrip hopindie popindie rockalternative hip hopOccupation(s)SingersongwritermusicianInstrument(s)VocalsguitarkeyboardsukulelebassdrumstambourineYears active1993–presentLabelsIndependienteHonest Jon'sMusical artist Martina Gillian To...
Polish painter Marcin ZaleskiMarcin Zaleski, Self-Portrait, 1840Born1796Kraków, PolandDied1877Warsaw, PolandNationalityPolishKnown forPainting Marcin Zaleski (1796 – 16 September 1877) was a Polish painter, a representative of Neoclassicism, considered the greatest Polish vedutist of the 19th century.[1] He mostly painted the cityscapes of Warsaw, Kraków and Vilnius. Biography Zaleski was born in Kraków. He received his education in Kraków and Warsaw. In 1817−1822, Za...
British retired officer For the two Australian sportsmen of the same name, see Barry Thornton (cricketer) and Barry Thornton (footballer). Sir Barry Michael ThorntonAir Marshal Sir Barry Thornton in March 2007AllegianceUnited KingdomService/branchRoyal Air ForceYears of service1976–2009RankAir MarshalCommands heldAir Member for Material (2007–09)Personnel and Training Command (2006–07)Air Member for Logistics (2004–06)Battles/warsGulf WarAwardsKnight Commander of the Order of the...
American actor (1925–2002) Rod SteigerSteiger in Al Capone (1959)Born(1925-04-14)April 14, 1925Westhampton, New York, U.S.DiedJuly 9, 2002(2002-07-09) (aged 77)Los Angeles, California, U.S.OccupationActorYears active1946–2002WorksFull listAwardsFull list Rodney Stephen Steiger (/ˈstaɪɡər/ STY-gər; April 14, 1925 – July 9, 2002) was an American actor, noted for his portrayal of offbeat, often volatile and crazed characters. Ranked as one of Hollywood's most charismatic and...
Takur Periode Pleistocene to Recent Megalaimidae Fire-tufted barbetTaksonomiKerajaanAnimaliaFilumChordataKelasAvesOrdoPiciformesFamiliMegalaimidae Blyth, 1852 GeneraPsilopogonCaloramphuslbs Megalaimidae, burung takur, adalah keluarga burung, terdiri dari dua genera dengan 34 spesies asli hutan di wilayah Indomalayan dari Tibet hingga Indonesia . Mereka pernah disatukaj dengan burung lain dalam famili Capitonidae tetapi spesies Dunia Lama ditemukan memiliki ciri khas dan dianggap, bersama deng...
Posiciones del Polo Norte Magnético El desplazamiento polar es el movimiento de un polo en relación con algún marco de referencia. Se puede utilizar, por ejemplo, para medir el grado en que se ha observado que los polos magnéticos de la Tierra se mueven en relación con el eje de rotación de la Tierra. También es posible usar continentes como referencia y observar el movimiento relativo del polo magnético en relación con los diferentes continentes; al hacerlo, el movimiento relativo d...
1534 treaty between Gujarat and Portugal Treaty of Baçaim (1534)Signed23 December 1534LocationAt sea, aboard the Portuguese galleon São MateusMediatorsAn envoy from the Ottoman EmpireNegotiators Nuno da Cunha Sultan Bahadur Signatories Kingdom of Portugal Sultanate of Gujarat The Treaty of Baçaim was signed by Sultan Bahadur of Gujarat and the Kingdom of Portugal on 23 December 1534 while on board the galleon São Mateus. Based on the terms of the agreement, the Portuguese Empire gained co...
Washington Heights dilihat dari menara barat Jembatan George Washington, jembatan kendaraan bermotor tersibuk di dunia.[1] Little Red Lighthouse terdapat di dasar menara timur. Washington Heights adalah sebuah permukiman di New York City yang terletak di tepi utara borough Manhattan. Permukiman ini dinamai menurut nama Fort Washington, sebuah benteng yang dibangun di titik tertinggi pulau Manhattan oleh Pasukan Kontinental pada Perang Revolusi Amerika Serikat untuk mempertahankan daer...
This biography of a living person relies on a single source. You can help by adding reliable sources to this article. Contentious material about living people that is unsourced or poorly sourced must be removed immediately. (November 2020) (Learn how and when to remove this template message) His EminenceHrizostom JevićMetropolitan Bishop of Dabar-BosnaHrizostom Jević in 2017 at the celebration of the 700th anniversary of the Tronoša monasteryChurchSerbian Orthodox ChurchMetropolisDabar-Bos...