query: how many cycles of cell division does mitosis undergo

pos: Cell cycle cells. In cells with a nucleus, as in eukaryotes, the cell cycle is also divided into three periods: interphase, the mitotic (M) phase, and cytokinesis. During interphase, the cell grows, accumulating nutrients needed for mitosis, preparing it for cell division and duplicating its DNA. During the mitotic phase, the chromosomes separate. During the final stage, cytokinesis, the chromosomes and cytoplasm separate into two new daughter cells. To ensure the proper division of the cell, there are control mechanisms known as cell cycle checkpoints. The cell-division cycle is a vital process by which a single-celled fertilized egg develops into a mature

pos: Mitosis 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. The mitotic phase is a relatively short period of the cell cycle. It alternates with the much longer "interphase", where the cell prepares itself for the process of cell division. Interphase is divided into three phases: G (first gap), S

pos: Mitosis three or more daughter cells instead of the normal two is a mitotic error called tripolar mitosis or multipolar mitosis (direct cell triplication / multiplication). Other errors during mitosis can induce apoptosis (programmed cell death) or cause mutations. Certain types of cancer can arise from such mutations. Mitosis occurs only in eukaryotic cells. Prokaryotic cells, which lack a nucleus, divide by a different process called binary fission. Mitosis varies between organisms. For example, animal cells undergo an "open" mitosis, where the nuclear envelope breaks down before the chromosomes separate, whereas fungi undergo a "closed" mitosis, where chromosomes divide within an

pos: Endoreduplication endomitosis. An alternative pathway is an ordinary mitosis-again without cell division instead of one of the endomitotic cycles. The cytological picture in the tapetum is further complicated by restitution in anaphase and fusion of metaphase and anaphase groups during mitosis, processes which could give rise to cells with one, two, or three nuclei, instead of the expected two or four. No sign of the so-called "inhibited" mitosis is seen in these tapetal cells. When the PMCs are in leptotene-zygotene, very few tapetal nuclei are in endomitosis. When the PMCs have reached diplotene, almost 100% of cells which are not in

pos: Microgametogenesis These microspore mother cells, also called microsporocytes, then undergo meiosis and become four microspore haploid cells. These new microspore cells then undergo mitosis and form a tube cell and a generative cell. The generative cell then undergoes mitosis one more time to form two male gametes, also called sperm. Microgametogenesis Microgametogenesis is the process in plant reproduction where a microgametophyte develops in a pollen grain to the three-celled stage of its development. In flowering plants it occurs with a microspore mother cell inside the anther of the plant. When the microgametophyte is first formed inside the pollen grain four sets

pos: Trichomonas describe this form as a pseudocystic form. In its trophozoite form, "Trichomonas" undergoes cell division through an interesting process called cryptopleuromitosis. There are three common forms of mitosis: open, closed, and semi-open. In open mitosis, the nuclear envelope disappear so that mitotic spindles can interact with the chromosomes. In closed mitosis, the nuclear envelope does not disappear but mitotic spindles appear within the nucleus to separate the chromosomes. In semi-open mitosis, the nuclear envelope remains intact but the mitotic spindles pierce through the nuclear envelope to divide the chromosomes. Cryptopleuromitosis is different from all the other more commonly known methods

pos: Cell division the amount of cyclin increases, more and more cyclin dependent kinases attach to cyclin signaling the cell further into interphase. The peak of the cyclin attached to the cyclin dependent kinases this system pushes the cell out of interphase and into the M phase, where mitosis, meiosis, and cytokinesis occur. There are three transition checkpoints the cell goes through before entering the M phase. The most important being the G1-S transition checkpoint. If the cell does not pass this phase, then the cell will most likely not go through the rest of the cell division cycle. Prophase is the first

pos: Nondisjunction form of cell division that involves ordered distribution of chromosomal material. Higher animals have three distinct forms of such cell divisions: Meiosis I and meiosis II are specialized forms of cell division occurring during generation of gametes (eggs and sperm) for sexual reproduction, mitosis is the form of cell division used by all other cells of the body. Ovulated eggs become arrested in metaphase II until fertilization triggers the second meiotic division. Similar to the segregation events of mitosis, the pairs of sister chromatids resulting from the separation of bivalents in meiosis I are further separated in anaphase of meiosis

pos: Extrachromosomal array Extrachromosomal array An extrachromosomal array is a method for mosaic analysis in genetics. It is a cosmid, and contains two functioning (wild-type) closely linked genes: a "gene of interest" and a "mosaic marker". Such an array is injected into germ line cells, which already contain mutant (specifically, loss of function) alleles of all three genes in their chromosomal DNA. The cosmid, which is not packed correctly during mitosis, is occasionally present in only one daughter cell following cell division. The daughter cell containing the array expresses the gene of interest; the cell lacking the array does not. The "mosaic marker"

neg: Homologous chromosome the same in mitosis as they do in meiosis. Prior to every single mitotic division a cell undergoes, the chromosomes in the parent cell replicate themselves. The homologous chromosomes within the cell will ordinarily not pair up and undergo genetic recombination with each other. Instead, the replicants, or sister chromatids, will line up along the metaphase plate and then separate in the same way as meiosis II - by being pulled apart at their centromeres by nuclear mitotic spindles. If any crossing over does occur between sister chromatids during mitosis, it does not produce any new recombinant genotypes. Homologous pairing

neg: Cell division in order for the genetic content to be maintained. During G2, the cell undergoes the final stages of growth before it enters the M phase, where spindles are synthesized. The M phase, can be either mitosis or meiosis depending on the type of cell. Germ cells, or gametes, undergo meiosis, while somatic cells will undergo mitosis. After the cell proceeds successfully through the M phase, it may then undergo cell division through cytokinesis. The control of each checkpoint is controlled by cyclin and cyclin dependent kinases. The progression of interphase is the result of the increased amount of cyclin. As

neg: Cell nucleus mitosis. However, this disassembly of the nucleus is not a universal feature of mitosis and does not occur in all cells. Some unicellular eukaryotes (e.g., yeasts) undergo so-called closed mitosis, in which the nuclear envelope remains intact. In closed mitosis, the daughter chromosomes migrate to opposite poles of the nucleus, which then divides in two. The cells of higher eukaryotes, however, usually undergo open mitosis, which is characterized by breakdown of the nuclear envelope. The daughter chromosomes then migrate to opposite poles of the mitotic spindle, and new nuclei reassemble around them. At a certain point during the cell cycle

neg: Cell (biology) into two daughter cells. This leads to growth in multicellular organisms (the growth of tissue) and to procreation (vegetative reproduction) in unicellular organisms. Prokaryotic cells divide by binary fission, while eukaryotic cells usually undergo a process of nuclear division, called mitosis, followed by division of the cell, called cytokinesis. A diploid cell may also undergo meiosis to produce haploid cells, usually four. Haploid cells serve as gametes in multicellular organisms, fusing to form new diploid cells. DNA replication, or the process of duplicating a cell's genome, always happens when a cell divides through mitosis or binary fission. This occurs during

neg: Cell growth inhibition of Wee1. This finding shows how cell size plays a direct role in regulating the start of mitosis. In this model, Pom1 acts as a molecular link between cell growth and mitotic entry through a Cdr2-Cdr1-Wee1-Cdk1 pathway. The Pom1 polar gradient successfully relays information about cell size and geometry to the Cdk1 regulatory system. Through this gradient, the cell ensures it has reached a defined, sufficient size to enter mitosis. Many different types of eukaryotic cells undergo size-dependent transitions during the cell cycle. These transitions are controlled by the cyclin-dependent kinase Cdk1. Though the proteins that control Cdk1 are

neg: Mitosis intact cell nucleus. 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. Numerous descriptions of cell division were made during 18th and 19th centuries, with various degrees of accuracy. In 1835, the German botanist Hugo von Mohl, described cell division in the green alga "Cladophora glomerata", stating that multiplication of cells occurs through cell division. In 1838, Schleiden affirmed that the

neg: Cell cycle to opposite sides of the cell. Mitosis occurs exclusively in eukaryotic cells, but occurs in different ways in different species. For example, animals undergo an "open" mitosis, where the nuclear envelope breaks down before the chromosomes separate, while fungi such as "Aspergillus nidulans" and "Saccharomyces cerevisiae" (yeast) undergo a "closed" mitosis, where chromosomes divide within an intact cell nucleus. Prokaryotic cells, which lack a nucleus, divide by a process called binary fission. Mitosis is immediately followed by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly equal shares of these cellular components. Mitosis and

neg: Amitosis Amitosis Amitosis ("a-" + "mitosis") is cell proliferation that does not occur by mitosis, the mechanism usually identified as essential for cell division in eukaryotes. The polyploid macronucleus found in Ciliates divides amitotically. While normal mitosis results in a precise division of parental alleles amitosis results in a random distribution of parental alleles. Ploidy levels of >1000 in some species means both parental alleles can be maintained over many generations, while species with fewer numbers of each chromosome will tend to become homozygous for one or the other parental allele through a process known as phenotypic or allelic assortment. It

neg: Green algae with flat cristae. When present, paired flagella are used to move the cell. They are anchored by a cross-shaped system of microtubules and fibrous strands. Flagella are only present in the motile male gametes of charophytes bryophytes, pteridophytes, cycads and "Ginkgo", but are absent from the gametes of Pinophyta and flowering plants. Members of the class Chlorophyceae undergo closed mitosis in the most common form of cell division among the green algae, which occurs via a phycoplast. By contrast, charophyte green algae and land plants (embryophytes) undergo open mitosis without centrioles. Instead, a 'raft' of microtubules, the phragmoplast, is formed

neg: Cellular senescence longer replicate themselves through the process of cellular mitosis; i.e., cells experience "replicative senescence". How and why some cells become post-mitotic in some species has been the subject of much research and speculation, but it has been suggested that cellular senescence evolved as a way to prevent the onset and spread of cancer. Somatic cells that have divided many times will have accumulated DNA mutations and would therefore be in danger of becoming cancerous if cell division continued. As such, it is becoming apparent that senescent cells undergo conversion to an immunogenic phenotype that enables them to be eliminated by

neg: Preprophase band predicted by the position of the preprophase band. Preprophase band The preprophase band is a microtubule array found in plant cells that are about to undergo cell division and enter the preprophase stage of the plant cell cycle. Besides the phragmosome, it is the first microscopically visible sign that a plant cell is about to enter mitosis. The preprophase band was first observed and described by Jeremy Pickett-Heaps and Donald Northcote at Cambridge University in 1966. Just before mitosis starts, the preprophase band forms as a dense band of microtubules around the phragmosome and the future division plane just below

neg: Preprophase band Preprophase band The preprophase band is a microtubule array found in plant cells that are about to undergo cell division and enter the preprophase stage of the plant cell cycle. Besides the phragmosome, it is the first microscopically visible sign that a plant cell is about to enter mitosis. The preprophase band was first observed and described by Jeremy Pickett-Heaps and Donald Northcote at Cambridge University in 1966. Just before mitosis starts, the preprophase band forms as a dense band of microtubules around the phragmosome and the future division plane just below the plasma membrane. It encircles the nucleus at

neg: Neuroepithelial cell the subventricular zone (SVZ), the olfactory bulb and the dentate gyrus of the hippocampus. These cells do not appear in any of the peripheral nervous system. Often categorized as neural stem cells, neuroepithelial cells give rise to only a few varieties of neural cells, making them multipotent - a definite distinction from the pluripotent stem cells found in embryonic development. Neuroepithelial cells undergo mitosis generating more neuroepithelial cells, radial glial cells or progenitor cells, the latter two differentiating into either neurons or glial cells. The neuroepithelial cells undergo two different forms of mitosis: asymmetric differentiating division and symmetric prolific division.

neg: Maturation promoting factor is also present in somatic cells, where it induces entry into M phase of the mitotic cycle. Evidence that a diffusible factor regulates the entry into mitosis had been previously obtained in 1966 using the slime mold "Physarum polycephalum" in which the nuclei of the multi-nucleate plasmodial form undergo synchronous mitoses. Fusing plasmodia whose cell cycles were out of phase with each other led to a synchronous mitosis in the next mitotic cycle. This result demonstrated that mitotic entry was controlled by a diffusible cytoplasmic factor and not by a "nuclear clock." MPF is composed of two subunits: During G

neg: Saccharomyces cerevisiae of the cell cycle. Cytokinesis enables budding yeast "Saccharomyces cerevisiae" to divide into two daughter cells. "S. cerevisiae" forms a bud which can grow throughout its cell cycle and later leaves its mother cell when mitosis has completed. "S. cerevisiae" is relevant to cell cycle studies because it divides asymmetrically by using a polarized cell to make two daughters with different fates and sizes. Similarly, stem cells use asymmetric division for self-renewal and differentiation. For many cells, M phase does not happen until S phase is complete. However, for entry into mitosis in "S. cerevisiae" this is not true. Cytokinesis

neg: Carcinogen thus, their effect can be insidious. Cancer is any disease in which normal cells are damaged and do not undergo programmed cell death as fast as they divide via mitosis. Carcinogens may increase the risk of cancer by altering cellular metabolism or damaging DNA directly in cells, which interferes with biological processes, and induces the uncontrolled, malignant division, ultimately leading to the formation of tumors. Usually, severe DNA damage leads to programmed cell death, but if the programmed cell death pathway is damaged, then the cell cannot prevent itself from becoming a cancer cell. There are many natural carcinogens. Aflatoxin

neg: Phycoplast undergo "closed" mitosis where the nuclear envelope persists throughout mitosis. Phycoplast The phycoplast is a microtubule structure observed during cytokinesis in members of the "Chlorophyceae", the largest class of green algae. Cytokinesis in green algae occurs via a diverse range of mechanisms, including cleavage furrows in some algae and cell plates in others. Some green algae of the class "Charophyceae" use phragmoplasts similar to those in embryophytes to organize and guide the growing cell plate. In these algae, the microtubules of the telophase spindle give rise to the phragmoplast and are oriented perpendicular to the plane of cell division and

neg: Mitosis 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 the more similar to bacterial division. Mitotic cells can be visualized microscopically by staining them with fluorescent antibodies and dyes. Mitosis In cell biology, mitosis () is a part of the cell cycle when replicated chromosomes are separated into two new nuclei. Cell division

neg: Symbiodinium hence, in published literature, the alga in hospite is often referred to as a vegetative cyst. The term "cyst" usually refers to a dormant, metabolically quiescent stage in the life history of other dinoflagellates, initiated by several factors, including nutrient availability, temperature, and day length. Such cysts permit extended resistance to unfavourable environmental conditions. Coccoid "Symbiodinium" cells are metabolically active, as they photosynthesize, undergo mitosis, and actively synthesize proteins and nucleic acids. While most dinoflagellates undergo mitosis as a mastigote, in "Symbiodinium", mitosis occurs exclusively in the coccoid cell. The coccoid cell is surrounded by a cellulosic, usually smooth cell

neg: Schizosaccharomyces pombe in diameter, that grows entirely by elongation at the ends. After mitosis, division occurs by the formation of a septum, or cell plate, that cleaves the cell at its midpoint. The central events of cell reproduction are chromosome duplication, which takes place in S (Synthetic) phase, followed by chromosome segregation and nuclear division (mitosis) and cell division (cytokinesis), which are collectively called M (Mitotic) phase. G1 is the gap between M and S phases, and G2 is the gap between S and M phases. In the budding yeast, the G1 phase is particularly extended, and cytokinesis (daughter-cell segregation) does not

neg: Marteilia similar genera "Paramarteilia" and "Paramyxa" have bicellular and tetracellular spores respectively (Feist, Hine, Bateman, Stentiford, & Longshaw, 2009). "Marteilia"’s morphology is derived from its unique cell cycle. The primary cell undergoes mitosis and produces the secondary cell within the primary cell rather than outside the primary cell. The secondary cell then undergoes mitosis to produce more secondary cells. After reaching a certain number of secondary cells, each secondary cell then undergoes mitosis to produce a spore within itself. The spores undergo a series of endogenous mitosis until it becomes a tricellular spore (Feist, Hine, Bateman, Stentiford, & Longshaw, 2009). "Marteilia"

neg: Amitosis DNA content. Placenta, May;22(5):490-8. Zybina EV, Zybina TG, Bogdanova MS, Stein GI 2005 Cell Biol Int. 29 (12): 1066-1070 Zybina EV, Zybina TG. 2008, Modifications of nuclear envelope during differentiation and depolyploidization of rat trophoblast cells. Micron. 39(5):593-606. Epub 2007 May 31. Amitosis Amitosis ("a-" + "mitosis") is cell proliferation that does not occur by mitosis, the mechanism usually identified as essential for cell division in eukaryotes. The polyploid macronucleus found in Ciliates divides amitotically. While normal mitosis results in a precise division of parental alleles amitosis results in a random distribution of parental alleles. Ploidy levels of >1000 in

neg: Pollination year two sperm cells are produced by mitosis of the body cell of the male gametophyte. The pollen tube elongates and pierces and grows through the megasporangium wall and delivers the sperm cells to the female gametophyte inside. Fertilisation takes place when the nucleus of one of the sperm cells enters the egg cell in the megagametophyte’s archegonium. In flowering plants, the anthers of the flower produce microspores by meiosis. These undergo mitosis to form male gametophytes, each of which contains two haploid cells. Meanwhile, the ovules produce megaspores by meiosis, further division of these form the female gametophytes, which

neg: Mitogen also play a role in the regulation of PTGS2. Mitogen A mitogen is a chemical substance that encourages a cell to commence cell division, triggering mitosis. A mitogen is usually some form of protein. Mitogenesis is the induction (triggering) of mitosis, typically via a mitogen. Mitogens trigger signal transduction pathways in which mitogen-activated protein kinase (MAPK) is involved, leading to mitosis. Mitogens act primarily by influencing a set of proteins which are involved in the restriction of progression through the cell cycle. The G1 checkpoint is controlled most directly by mitogens: further cell cycle progression does not need mitogens to

neg: Mitogen Mitogen A mitogen is a chemical substance that encourages a cell to commence cell division, triggering mitosis. A mitogen is usually some form of protein. Mitogenesis is the induction (triggering) of mitosis, typically via a mitogen. Mitogens trigger signal transduction pathways in which mitogen-activated protein kinase (MAPK) is involved, leading to mitosis. Mitogens act primarily by influencing a set of proteins which are involved in the restriction of progression through the cell cycle. The G1 checkpoint is controlled most directly by mitogens: further cell cycle progression does not need mitogens to continue. The point where mitogens are no longer needed

neg: Multipolar spindles cancer cells is one of many differences from normal cells which can be seen under a microscope. Cancer is defined by uncontrolled cell growth and malignant cells can undergo cell division with multipolar spindles because they can group multiple centrosomes into two spindles. These multipolar spindles are often assembled early in mitosis and rarely seen towards the later stages. Research has shown possible causes of formation of multipolar spindles. A possible causes of multipolar spindle formation involve regulation of protein kinase family known as Aurora kinase. Aurora kinase has two forms which are designated Aurora kinase A and Aurora kinase

neg: Iain Mattaj important contributions to our knowledge concerning how RNA and proteins are transported between the cell nucleus and cytoplasm. These findings stemmed from his early work on the import and export of ribonucleoproteins particles — RNA–protein complexes — at the cell nucleus. Iain subsequently uncovered the role of enzymes known as GTPases in the regulation of mitosis — the division of the cell nucleus into two daughter nuclei. Under the influence of Ran, a GTPase signalling protein, the cell cytoskeleton remodels to form the mitotic spindle — a crucial structure in mitosis. By dissecting Ran's role in facilitating mitosis, Iain is

neg: Booster dose and some such as tetanus need boosters. The prevailing theory is that if the immune system responds to a primary vaccine rapidly, the body does not have time to sufficiently develop immunological memory against the disease, and memory cells will not persist in high numbers for the lifetime of the human. After a primary response of the immune system against a vaccination, memory T helper cells and B cells persist at a fairly constant level in germinal centers, undergoing cell division at a slow to nonexistent rate. While these cells are long-lived, they do not typically undergo mitosis, and eventually

neg: Microtubule organizing center cell. Movements of the microtubules are based on the actions of the centrosome. Each daughter cell after the cessation of mitosis contains one primary MTOC. Before cell division begins, the interphase MTOC replicates to form two distinct MTOCs (now typically referred to as centrosomes). During cell division, these centrosomes move to opposite ends of the cell and nucleate microtubules to help form the mitotic/meiotic spindle. If the MTOC does not replicate, the spindle cannot form, and mitosis ceases prematurely. γ-tubulin is a protein located at the centrosome that nucleates the microtubules by interacting with the tubulin monomer subunit in the

neg: Gametogenesis of gametogenesis and the sexual cycle), some authors emphasize diversity, and others emphasize DNA repair. Gametogenesis Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic division of diploid gametocytes into various gametes, or by mitosis. For example, plants produce gametes through mitosis in gametophytes. The gametophytes grow from haploid spores after sporic meiosis. The existence of a multicellular, haploid phase in the life cycle between meiosis and gametogenesis is also referred to as alternation

neg: Gametogenesis Gametogenesis Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic division of diploid gametocytes into various gametes, or by mitosis. For example, plants produce gametes through mitosis in gametophytes. The gametophytes grow from haploid spores after sporic meiosis. The existence of a multicellular, haploid phase in the life cycle between meiosis and gametogenesis is also referred to as alternation of generations. Animals produce gametes directly through meiosis in organs called gonads (testis in males

neg: Tetraselmis production. For example, the species "T. indica" is being used to study how asymmetric cell-division during mitosis results in clonal cell heterogeneity. This species forms a clonal colony in which the cells are morphologically and ultrastructurally different, and many cells specialize and develop independent physical properties. The asymmetric division of daughter cells results in the unequal division of both cytoplasm and nucleoplasm. Scientists believe this phenomenon allows clones to form “sub-populations” that remain close to one another, in which the cells cooperate with one another and act as one large population. Asymmetric cell division clearly plays an important role in

neg: Klerokinesis The group generated a population of human retinal pigment epithelial (RPE) cells that would undergo karyokinesis but miss the cytokinesis stage. Using live cell imaging, klerokinesis was found while studying human RPE cells to establish the hypothesis of German biologist Theodor Boveri, that the presence of an abnormal number of sets of chromosomes in a cell (polyploidy) would lead to out-of-control cell division, causing cancer. However, contrary to Boveri's hypothesis, researchers found that abnormal cell division rarely has long-term negative effects in human cells, rather, some cell divisions occurred later than the end of mitosis in such a way that

neg: Cell cycle cytokinesis together define the division of the mother cell into two daughter cells, genetically identical to each other and to their parent cell. This accounts for approximately 10% of the cell cycle. Because cytokinesis usually occurs in conjunction with mitosis, "mitosis" is often used interchangeably with "M phase". However, there are many cells where mitosis and cytokinesis occur separately, forming single cells with multiple nuclei in a process called endoreplication. This occurs most notably among the fungi and slime moulds, but is found in various groups. Even in animals, cytokinesis and mitosis may occur independently, for instance during certain stages

neg: Microfluidic whole genome haplotyping a metaphase cell – remain difficult and labour intensive. Other automated techniques for metaphase cell separation would improve throughput. In addition, this method is only applicable to cells in metaphase, which inherently limits the technique to cell types and tissues that undergo mitosis. Single cell analysis does not account for the possibility of mosaicism; therefore, applications in cancer diagnosis and research would necessarily require processing of multiple cells. Finally, since this entire process is based on amplification from a single cell, the accuracy of any genetic analysis is limited to the ability of commercially available platforms to produce sufficient amounts

neg: Mitotic cell rounding Mitotic cell rounding Mitotic cell rounding is a shape change that occurs in most animal cells that undergo mitosis. Cells abandon the spread or elongated shape characteristic of interphase and contract into a spherical morphology during mitosis. The phenomena is seen both in artificial cultures "in vitro" and naturally forming tissue "in vivo". In 1935, one of the first published accounts of mitotic rounding in live tissue described cell rounding in the pseudostratified epithelium of the mammalian neural tube. Sauer noticed that cells in mitosis rounded up to the apical, or luminal, surface of the columnar epithelium before dividing and

neg: Germ cell cells produce gametes and are the only cells that can undergo meiosis as well as mitosis. These cells are sometimes said to be immortal because they are the link between generations. Somatic cells are all the other cells that form the building blocks of the body and they only divide by mitosis. The lineage of germ cells is called germ line. Germ cell specification begins during cleavage in many animals or in the epiblast during gastrulation in birds and mammals. After transport, involving passive movements and active migration, germ cells arrive at the developing gonads. In humans, sexual differentiation starts

neg: Meiosis by mitosis, developing into the haploid gametophyte generation, which then gives rise to gametes directly (i.e. without further meiosis). In both animals and plants, the final stage is for the gametes to fuse, restoring the original number of chromosomes. In females, meiosis occurs in cells known as oocytes (singular: oocyte). Each primary oocyte divides twice in meiosis, unequally in each case. The first division produces a daughter cell, and a much smaller polar body which may or may not undergo a second division. In meiosis II, division of the daughter cell produces a second polar body, and a single haploid

neg: Cell division in the first division, and sister chromatids are separated in the second division. 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. Prokaryotes (bacteria) undergo a vegetative cell division known as binary fission, where their genetic material is segregated equally into two daughter cells. All cell divisions, regardless of organism, are preceded by a single round of DNA replication. For simple unicellular microorganisms such as the amoeba, one cell division is equivalent to reproduction – an

neg: Mitotic catastrophe cell death in cancer cells treated with ionizing radiation. Not all cells die immediately following abnormal mitosis caused by mitotic catastrophe, but many do. Cells that do not immediately die are likely to create aneuploid cells following subsequent attempts at cell division posing a risk of oncogenesis (i.e. potentially leading to cancer). A very small fraction of these aneuploid cells produced by mitotic catastrophe might later reduce DNA ploidy by reductive division involving meiotic cell division pathways. Mitotic catastrophe Mitotic catastrophe refers to a mechanism of delayed mitosis-linked cell death, a sequence of events resulting from premature or inappropriate entry

neg: Reticulomyxa many haploid nuclei, approximately 5 µm in diameter. Cysts produced by "Reticulomyxa" can be covered or uncovered. Covered cysts are enclosed by two layers, with the outer mucus layer being much thicker. Uncovered cysts do not have the thick outer layer as seen in covered cysts and have irregular sizes. Plasmodia of this genera have only been seen to undergo mitosis in culture conditions. Asexual reproduction through multiple fission, where the nuclei will undergo many rounds of mitotic division before the cytoplasm separates. In "Reticulomyxa," mitosis is closed, the nuclear membrane remains intact during spindle formation and chromosome separation. Under

neg: Mitosis Mitosis In cell biology, mitosis () is a part of the cell cycle when replicated chromosomes are separated into two new nuclei. Cell division gives rise to genetically identical cells in which the number of chromosomes is maintained. In general, mitosis (division of the nucleus) is preceded by the S stage of interphase (during which the DNA is replicated) and is often accompanied or followed by cytokinesis, which divides the cytoplasm, organelles and cell membrane into two new cells containing roughly equal shares of these cellular components. Mitosis and cytokinesis together define the mitotic (M) phase of an animal cell

neg: Jonathon Pines Cambridge then the Institute of Cancer Research in 2015. Pines research investigates cyclin, the cell cycle and mitosis. He pioneered the use of fluorescent tags to analyse the dynamic behaviour and stability of these regulators in living cells. Pines discoveries have revealed that mitotic regulators are targeted to specific substructures at specific times, and that mitosis is exquisitely coordinated by the destruction of key regulators at different times in cell division. Pines work has provided insights into how chromosome behaviour in mitosis controls both the time and the rate at which essential mitotic regulators are destroyed, and these discoveries have

neg: Nuclear envelope surface area and doubles its number of nuclear pore complexes. In eukaryotes, such as yeast, which undergo closed mitosis, the nuclear membrane stays intact during cell division. The spindle fibers either form within the membrane, or penetrate it without tearing it apart. In other eukaryotes (animals as well as plants), the nuclear membrane must break down during the prometaphase stage of mitosis to allow the mitotic spindle fibers to access the chromosomes inside. The breakdown and reformation processes are not well understood. In mammals, the nuclear membrane can break down within minutes, following a set of steps during the early

neg: Endoreduplication degradation of E2F. Post-transcriptional regulation of cyclin E-Cdk2 activity involves Ago/Fbw7-mediated proteolytic degradation of cyclin E and direct inhibition by factors such as Dacapo and p57. True endomitosis in the anther tapetum of the liliaceous plant Eremurus is described. The nuclear membrane does not disappear, but during metaphase the chromosomes are condensed, often considerably more than in normal mitosis. When the pollen mother cells (PMCs) go through the last premeiotic mitosis, the tapetal cells have one diploid nucleus which divides while the cell remains undivided. The two diploid nuclei may undergo an endomitosis and the resulting tetraploid nuclei a second

neg: Cellular adaptation number of cells. It is the result of increased cell mitosis, or division. The two types of physiologic hyperplasia are compensatory and hormonal. Compensatory hyperplasia permits tissue and organ regeneration. It is common in epithelial cells of the epidermis and intestine, liver hepatocytes, bone marrow cells, and fibroblasts. It occurs to a lesser extent in bone, cartilage, and smooth muscle cells. Hormonal hyperplasia occurs mainly in organs that depend on estrogen. For example, the estrogen-dependent uterine cells undergo hyperplasia and hypertrophy following pregnancy. Pathologic hyperplasia is an abnormal increase in cell division. A common pathologic hyperplasia in women occurs in

neg: Biological life cycle meiosis, also called somatic meiosis, which is a rare phenomenon. Vegetative meiosis can occur in haplodiplontic and also in diplontic life cycles. The gametophytes remain attached to and part of the sporophyte. Vegetative (non-reproductive) diploid cells undergo meiosis, generating vegetative haploid cells. These undergo many mitosis, and produces gametes. A different phenomenon, called vegetative diploidization, a type of apomixis, occurs in some brown algae (e.g., "Elachista stellaris"). Cells in a haploid part of the plant spontaneously duplicate their chromosomes to produce diploid tissue. The primitive type of life cycle probably had haploid individuals with asexual reproduction. Bacteria and archaea exhibit

neg: Tetraselmis non-motile stage, producing two daughter cells, and most species only undergo one division cycle. During cell division, organelles divide synchronously before nuclear division. Cell division is aided by a phycoplast, which is a microtubule structure that helps the cell divide the nuclei into each daughter cell. Daughter cells can develop into flagellated cells or remain non-motile, depending on environmental conditions. Additionally, vegetative cells whether flagellate or immotile are anchored to the thecal wall by four microtubule contact points. "Tetraselmis" species have been important for cellular biology research, for studying plankton growth cycles, and they may have future use in biofuel

neg: Saccharomyces cerevisiae of yeast cells can survive and grow: haploid and diploid. The haploid cells undergo a simple lifecycle of mitosis and growth, and under conditions of high stress will, in general, die. This is the asexual form of the fungus. The diploid cells (the preferential 'form' of yeast) similarly undergo a simple lifecycle of mitosis and growth. The rate at which the mitotic cell cycle progresses often differs substantially between haploid and diploid cells. Under conditions of stress, diploid cells can undergo sporulation, entering meiosis and producing four haploid spores, which can subsequently mate. This is the sexual form of the

neg: Endoreduplication new cell membrane and it often occurs in cells that have already differentiated. As such it may represent an energetically efficient alternative to cell proliferation among differentiated cell types that can no longer afford to undergo mitosis. While evidence establishing a connection between ploidy and tissue size is prevalent in the literature, contrary examples also exist. In developing plant tissues the transition from mitosis to endoreplication often coincides with cell differentiation and morphogenesis. However it remains to be determined whether endoreplication and polypoidy contribute to cell differentiation or vice versa. Targeted inhibition of endoreplication in trichome progenitors results in the

neg: Interphase later cell division, so the name was changed. A common misconception is that interphase is the first stage of mitosis. However, since mitosis is the division of the nucleus, prophase is actually the first stage. In interphase, the cell gets itself ready for mitosis or meiosis. Somatic cells, or normal diploid cells of the body, go through mitosis in order to reproduce themselves through cell division, whereas diploid germ cells (i.e., primary spermatocytes and primary oocytes) go through meiosis in order to create haploid gametes (i.e., sperm and ova) for the purpose of sexual reproduction. Chromosomes are copied. There are

neg: Adult stem cell and therefore behave as stem cells. However, some recent studies suggest that this behaviour is induced by the culture conditions in progenitor cells, the progeny of stem cell division that normally undergo a strictly limited number of replication cycles "in vivo". Furthermore, neurosphere-derived cells do not behave as stem cells when transplanted back into the brain. Neural stem cells share many properties with haematopoietic stem cells (HSCs). Remarkably, when injected into the blood, neurosphere-derived cells differentiate into various cell types of the immune system. Olfactory adult stem cells have been successfully harvested from the human olfactory mucosa cells, which are

neg: Cell nucleus microtubules come in contact with chromosomes, whose centromeric regions are incorporated into the nuclear envelope (the so-called closed mitosis with extranuclear spindle). In many other protists (e.g., ciliates, sporozoans) and fungi, the centrosomes are intranuclear, and their nuclear envelope also does not disassemble during cell division. Apoptosis is a controlled process in which the cell's structural components are destroyed, resulting in death of the cell. Changes associated with apoptosis directly affect the nucleus and its contents, for example, in the condensation of chromatin and the disintegration of the nuclear envelope and lamina. The destruction of the lamin networks is controlled

neg: Mitotic cell rounding have recently been implicated in mitotic cell rounding. These include Parkinson’s disease associated DJ-1/Park7 and FAM134A/RETREG2. Mitotic cell rounding Mitotic cell rounding is a shape change that occurs in most animal cells that undergo mitosis. Cells abandon the spread or elongated shape characteristic of interphase and contract into a spherical morphology during mitosis. The phenomena is seen both in artificial cultures "in vitro" and naturally forming tissue "in vivo". In 1935, one of the first published accounts of mitotic rounding in live tissue described cell rounding in the pseudostratified epithelium of the mammalian neural tube. Sauer noticed that cells in

neg: Blastula cleavage occurs with only the synthesis and mitosis phases of the cell cycle. The addition of the two growth phases into the cell cycle allows for the cells to increase in size, as up to this point the blastomeres undergo reductive divisions in which the overall size of the embryo does not increase, but more cells are created. This transition begins the growth in size of the organism. The mid-blastula transition is also characterised by a marked increase in transcription of new, non-maternal mRNA transcribed from the genome of the organism. Large amounts of the maternal mRNA are destroyed at

neg: Physical oncology - is the sum of the cellular and tissue phenotype. The phenotype of the cell is supposed to be the translation of the genotype (and of the environment: epigenetics) expressed in a given cell: thus, a liver cell does not look like a pancreas cell at all because it does not express the same genes (yet all present in the genome of all cells). These characteristics are summarized by: differentiation, cell division (mitosis), apoptosis (or "cell suicide") and cell death. The doctor in charge of the diagnosis under the microscope (the pathologist) will describe the biopsy based on these criteria.

neg: Rho family of GTPases stimulate actin polymerization are the Arp2/3 proteins and the Diaphanous-related formins. Rho/Rac proteins are involved in a wide variety of cellular functions such as cell polarity, vesicular trafficking, the cell cycle and transcriptomal dynamics. Animal cells form many different shapes based on their function and location in the body. Rho proteins help cells regulate changes in shape throughout their life-cycle. Before cells can undergo key processes such as budding, mitosis, or locomotion, it must have some manner of cell polarity. One example of Rho GTPases' role in cell polarity is seen in the much-studied yeast cell. Before the cell can

neg: Cleavage (embryo) are pushed to one side of the cavity (because the embryo isn't getting any bigger) to form the inner cell mass (ICM) and will give rise to the embryo and some extraembryonic membranes. At this stage, the embryo is called a blastocyst. Cleavage (embryo) In embryology, cleavage is the division of cells in the early embryo. The process follows fertilization, with the transfer being triggered by the activation of a cyclin-dependent kinase complex. The zygotes of many species undergo rapid cell cycles with no significant overall growth, producing a cluster of cells the same size as the original zygote. The

neg: Karyogamy cell, called a zygote or zygospore can then enter meiosis (a process of chromosome duplication, recombination, and division, to produce four new haploid cells), or continue to divide by mitosis. Mammalian fertilization uses a comparable process to combine haploid sperm and egg cells (gametes) to create a diploid fertilized egg. The term karyogamy comes from the Greek "karyo-" (from κάρυον "karyon") meaning "nut" and γάμος "gamos", meaning "marriage". Haploid organisms such as fungi, yeast, and algae can have complex cell cycles, in which the choice between sexual or asexual reproduction is fluid, and often influenced by the environment. Some organisms,

neg: Tapetum (botany) Tapetum (botany) The tapetum is a specialised layer of nutritive cells found within the anther, of flowering plants, where it is located between the sporangenous tissue and the anther wall. Tapetum is important for the nutrition and development of pollen grains, as well as a source of precursors for the pollen coat. The cells are usually bigger and normally have more than one nucleus per cell. As the sporogenous cells undergo mitosis, the nuclei of tapetal cells also divide. Sometimes, this mitosis is not normal due to which many cells of mature tapetum become multinucleate. Sometimes polyploidy and polyteny can

neg: Coscinodiscophyceae never have a raphe. In terms of cell cycle, vegetative cells are diploid and undergo mitosis during normal cell division. In sexual species, oogamous meiosis produces haploid gametes, either ova or sperm cells. These fuse to produce a zygote which expands in size to develop into an auxospore from which full-sized vegetative cells are produced. In some taxonomy schemes, the centric diatoms are known instead as order Coscinodiscophyceae, and in some schemes as order Biddulphiales. However, diatom taxonomy is changing due to the development of new molecular and genetical analysis tools. Coscinodiscophyceae The Coscinodiscophyceae are a class of diatoms. They

neg: Asymmetric cell division These proteins are both synthesized in the neuroblast and segregate into only the GMC during divisions. Numb is a suppressor of Notch, therefore the asymmetric segregation of Numb to the basal cortex biases the response of the daughter cells to Notch signaling, resulting in two distinct cell fates. Prospero is required for gene regulation in GMCs. It is equally distributed throughout the neuroblast cytoplasm, but becomes localized at the basal cortex when the neuroblast starts to undergo mitosis. Once the GMC buds off from the basal cortex, Prospero becomes translocated into the GMC nucleus to act as a transcription factor.

neg: Nassula elongate, and uniformly ciliated, with a single macronucleus and a partial hypostomial frange ("synhymenium") running from the left side of the cell to the oral aperture. When food is scarce, members of the genus have the ability to become dormant by forming a microbial cyst. Excystment can be induced by exposure to a medium inoculated with wild bacteria. "Nassula" reproduce asexually, by fission. During reproduction, the cell is divided transversally. As in most ciliates (with the exception of the Karyorelictea) the macronucleus splits, during division, and the micronuclei also undergo mitosis. While fission is an asexual process, it may be

neg: Cell synchronization intermediate in the mevalonate pathway responsible for synthesis of cholesterol. Addition of cholesterol to Lovastatin-treated cells does not undo the arrest affect, so Lovastatin appears to inhibit the formation of some early intermediate in the pathway that is essential for progression through early G1. Mitotic selection is a drug-free procedure for the selection of mitotic cells from a monolayer undergoing exponential growth. During mitosis, cells undergo changes in morphology, and mitotic selection takes advantage of this in adherent cells grown in a monolayer. The cells become more spherical, decreasing the surface area of cell membrane attached to the culture plate.

neg: Pennales involved in gliding movements made by diatom cells; motile diatoms always possess a raphe. In terms of cell cycle, vegetative cells are diploid and undergo mitosis during normal cell division. Periodically, meiosis produces morphologically identical haploid gametes (isogametes), which fuse to produce a (sometimes binucleate) zygote that develops into an auxospore (from which full-sized vegetative cells are produced). In some taxonomic schemes, the pennate diatoms are divided into two groups: pennate diatoms without a raphe, known as araphids (order Fragilariophyceae), and pennate diatoms with a raphe, known as raphids (order Bacillariophyceae). Pennales The order Pennales is a traditional subdivision of

neg: Morphokinetics IVF derived from the egg and the sperm cell respectively and two tiny cells called polar bodies. 2. Cleavage This begins when the zygote divides into two cells via mitosis. The division continues such that each cell divides into another two cells, which results in a multiplying effect. 3. Morula The ball of cells formed after the multiple divisions is called a morula. It consists of about 16-32 cells in a ball within a translucent, elastic layer called the zona pellucida. It will then undergo compaction which is a process where the cells bind firmly together and continue to develop into

neg: Angelika Amon continues until reactivation of CDC28 toward the end of G1. The Amon lab primarily investigates yeast ("Saccharomyces cerevisiae") as a model for understanding the controls that govern cell-cycle progression. As a Whitehead Fellow, her team discovered that CDC20 plays a crucial role in cell division. Her Whitehead team identified an interaction between phosphatase and CDC14 which initiates the exit of cells from mitosis to the G1 phase. Amon's team demonstrated that CDC20 is the target protein in the spindle checkpoint during mitosis. Amon's more recent work has investigated the regulation of chromosome segregation and how chromosomes are accurately transmitted to

neg: Anaphase lag Anaphase lag Anaphase lag is a consequence of an event during cell division where sister chromatids do not properly separate from each other because of improper spindle formation. The chromosome or chromatid does not properly migrate during anaphase and the daughter cells will lose some genetic information. It is one of many causes of aneuploidy. This event can occur during both meiosis and mitosis with unique repercussions. In either case, anaphase lag will cause one daughter cell to receive a complete set of chromosomes while the other lacks one paired set of chromosomes, creating a form of monosomy. Whether the

neg: Xenopus TGF-beta superfamily signaling pathways and other important networks, such as the MAP kinase pathway and the Wnt pathway. Moreover, new methods using egg extracts revealed novel, important targets of the Wnt/GSK3 destruction complex. Cell division: "Xenopus" egg extracts have allowed the study of many complicated cellular events "in vitro". Because egg cytosol can support successive cycling between mitosis and interphase "in vitro", it has been critical to diverse studies of cell division. For example, the small GTPase Ran was first found to regulate interphase nuclear transport, but "Xenopus" egg extracts revealed the critical role of Ran GTPase in mitosis independent

neg: Meiosis by the location of the organism phase(s). In the "diplontic life cycle" (with pre-gametic meiosis), of which humans are a part, the organism is diploid, grown from a diploid cell called the zygote. The organism's diploid germ-line stem cells undergo meiosis to create haploid gametes (the spermatozoa for males and ova for females), which fertilize to form the zygote. The diploid zygote undergoes repeated cellular division by mitosis to grow into the organism. In the "haplontic life cycle" (with post-zygotic meiosis), the organism is haploid instead, spawned by the proliferation and differentiation of a single haploid cell called the gamete.

neg: Centrosome cycle. During the prophase in the process of cell division called mitosis, the centrosomes migrate to opposite poles of the cell. The mitotic spindle then forms between the two centrosomes. Upon division, each daughter cell receives one centrosome. Aberrant numbers of centrosomes in a cell have been associated with cancer. Doubling of a centrosome is similar to DNA replication in two respects: the semiconservative nature of the process and the action of CDK2 as a regulator of the process. But the processes are essentially different in that centrosome doubling does not occur by template reading and assembly. The mother centriole

neg: Nuclear dimorphism Tetrahymena is a useful research model for studying nuclear dimorphism; it maintains two distinct nuclear genomes, the micronucleus and the macronucleus. The micronucleus genome contains five chromosomes that undergo mitosis during micronuclear division and meiosis during conjugation, which is the sexual division of the micronucleus. The macronuclear genome is broken down and catabolized once per life cycle during conjugation, allowing it to be site-specific, and a new macronucleus differentiates from a mitotic descendant of the conjugated micronucleus. Nuclear dimorphism Nuclear dimorphism is a term referred to the special characteristic of having two different kinds of nuclei in a cell. This

neg: MClone cell type to the others (and to itself too). This last one is a number smaller than 1 that subtracts from the resultant force of the relaxation (thus, keeping the cells together). Each relaxation happens has a defined "day" in which it occurs (this is the way MClone calls the relaxation process). The number of relaxations per day is defined at the beginning of the algorithm. The mitosis rate is defined as a number that indicates in how many days a cell is going to reproduce "again". For example, if the mitosis rate of a given cell type is 4,

neg: Cell growth M phase, consists of nuclear division (karyokinesis) and cytoplasmic division (cytokinesis), accompanied by the formation of a new cell membrane. This is the physical division of "mother" and "daughter" cells. The M phase has been broken down into several distinct phases, sequentially known as prophase, prometaphase, metaphase, anaphase and telophase leading to cytokinesis. Cell division is more complex in eukaryotes than in other organisms. Prokaryotic cells such as bacterial cells reproduce by binary fission, a process that includes DNA replication, chromosome segregation, and cytokinesis. Eukaryotic cell division either involves mitosis or a more complex process called meiosis. Mitosis and meiosis

neg: Mitosis 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. 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. In plants, this structure coalesces into a cell plate at the center of the

neg: Reproduction from the same individual, e.g., many vascular plants, some foraminiferans, some ciliates. The term "autogamy" is sometimes substituted for autogamous pollination (not necessarily leading to successful fertilization) and describes self-pollination within the same flower, distinguished from geitonogamous pollination, transfer of pollen to a different flower on the same flowering plant, or within a single monoecious Gymnosperm plant. Mitosis and meiosis are types of cell division. Mitosis occurs in somatic cells, while meiosis occurs in gametes. Mitosis The resultant number of cells in mitosis is twice the number of original cells. The number of chromosomes in the offspring cells is the

neg: Origin and function of meiosis one of the two copies into each of the two daughter cells, and contrast with meiosis. The mitosis theory states that meiosis evolved from mitosis. On this theory, early eukaryotes evolved mitosis first, became established and only then did meiosis and sexual reproduction arise. Support for the idea that meiosis arose from mitosis is the observation that some features, such as the meiotic spindles that draw chromosome sets into separate daughter cells upon cell division, and processes regulating cell division, employ the same, or similar, molecular machinery. Yet there is no compelling evidence for a period in the early evolution

neg: Preprophase Preprophase Preprophase is an additional phase during mitosis in plant cells that does not occur in other eukaryotes such as animals or fungi. It precedes prophase and is characterized by two distinct events: Plant cells are fixed with regards to their neighbor cells within the tissues they are growing in. In contrast to animals where certain cells can migrate within the embryo to form new tissues, the seedlings of higher plants grow entirely based on the orientation of cell division and subsequent elongation and differentiation of cells within their cell walls. Therefore, the accurate control of cell division planes and

neg: G1 phase spreading. G1 phase The g phase, or Gap 1 phase, is the first of four phases of the cell cycle that takes place in eukaryotic cell division. In this part of interphase, the cell synthesizes mRNA and proteins in preparation for subsequent steps leading to mitosis. G phase ends when the cell moves into the S phase of interphase. G phase together with the S phase and G phase comprise the long growth period of the cell cycle called interphase that takes place before cell division in mitosis (M phase). During G phase, the cell grows in size and synthesizes

neg: G1 phase G1 phase The g phase, or Gap 1 phase, is the first of four phases of the cell cycle that takes place in eukaryotic cell division. In this part of interphase, the cell synthesizes mRNA and proteins in preparation for subsequent steps leading to mitosis. G phase ends when the cell moves into the S phase of interphase. G phase together with the S phase and G phase comprise the long growth period of the cell cycle called interphase that takes place before cell division in mitosis (M phase). During G phase, the cell grows in size and synthesizes mRNA

neg: Mitotic index the percentage of cells undergoing mitosis. Mitosis is the division of somatic cells when genetic information from one single cell is equally dispersed into two daughter cells. Durations of the cell cycle and mitosis vary in different cell types. An elevated mitotic index indicates more cells are dividing, and thus obvious in cancer cells, the mitotic index may be elevated during necessary processes to life, such as the normal growth of plants or animals, as well as cellular repair the site of an injury. The mitotic index is the number of cells undergoing mitosis divided by the number of cells

neg: Neuronal cell cycle 1998; Yang et al., 2003). Alzheimer diseased neurons rarely exhibit the ability to enter mitosis and, if they don’t undergo rapid mitosis, can survive for long periods of time in a tetraploid state. These neurons are able to enter the S phase and replicate their DNA, however they become blocked in the G2 state. In affected and unaffected tetraploid neurons, during development and during the progression of the disease, passing the G2/M checkpoint leads to cell death. This hints that the G2/M checkpoint aids in the survival of tetraploid neurons. This is supported by experiments in which the G2/M checkpoint

neg: Biochemical switches in the cell cycle and SBF. Biochemical switches in the cell cycle A series of biochemical switches control transitions between and within the various phases of the cell cycle. The cell cycle is a series of complex, ordered, sequential events that control how a single cell divides into two cells, and involves several different phases. The phases include the G1 and G2 phases, DNA replication or S phase, and the actual process of cell division, mitosis or M phase. During the M phase, the chromosomes separate and cytokinesis occurs. The switches maintain the orderly progression of the cell cycle and act as checkpoints to

neg: Biochemical switches in the cell cycle Biochemical switches in the cell cycle A series of biochemical switches control transitions between and within the various phases of the cell cycle. The cell cycle is a series of complex, ordered, sequential events that control how a single cell divides into two cells, and involves several different phases. The phases include the G1 and G2 phases, DNA replication or S phase, and the actual process of cell division, mitosis or M phase. During the M phase, the chromosomes separate and cytokinesis occurs. The switches maintain the orderly progression of the cell cycle and act as checkpoints to ensure that

neg: Meiomitosis to tumor and even from cell to cell. Research suggests that genomic instability affects the cancer cells' ability to metastasize. Cells able to effectively metastasize are more genomically stable than the rest of the local tumor bulk. Meiomitosis In cell biology, Meiomitosis is an aberrant cellular division pathway through which daughter cells following mitosis inherit partially expressed meiotic machinery. During normal mitosis, sister chromatids separate into two identical daughter cells. In meiosis is a diploid cell (2N) duplicates its DNA once and undergoes two rounds of cell division to produce four haploid (1N), germ cells that promotes the recombination of

neg: Nuclear pore fungi that undergo closed mitosis (where the nucleus does not disassemble), that the change of the permeability barrier of the NE was due to changes within the NPC and is what allows the entry of mitotic regulators. In Aspergillus nidulans NPC composition appears to be effected by the mitotic kinase NIMA, possibly by phosphorylating the nucleoporins Nup98 and Gle2/Rae1. This remodelling seems to allow the protein complex cdc2/cyclinB to enter the nucleus as well as many other proteins, such as soluble tubulin. The NPC scaffold remains intact throughout the whole closed mitosis. This seems to preserve the integrity of the

neg: Cleavage (embryo) Cleavage (embryo) In embryology, cleavage is the division of cells in the early embryo. The process follows fertilization, with the transfer being triggered by the activation of a cyclin-dependent kinase complex. The zygotes of many species undergo rapid cell cycles with no significant overall growth, producing a cluster of cells the same size as the original zygote. The different cells derived from cleavage are called blastomeres and form a compact mass called the morula. Cleavage ends with the formation of the blastula. Depending mostly on the amount of yolk in the egg, the cleavage can be holoblastic (total or entire

neg: Mitotic exit the eukaryotic cell cycle that are governed by systems-level control and feedback. Other examples of irreversible transition points include Start (irreversible commitment to a new cell division cycle) that can be explained by irreversible bistable switch whose control parameter is tightly regulated by the systemic feedbacks involving Cln2, Whi5, and SBF. Mitotic exit Mitotic Exit is an important transition point that signifies the end of mitosis and the onset of new G1 phase for a cell, and the cell needs to rely on specific control mechanisms to ensure that once it exits mitosis, it never returns to mitosis until it

neg: Biochemical switches in the cell cycle initiates mitotic entry. To conclude, spatial localization of cyclin B plays a role in mitotic entry. Translocation of cyclin B from the cytoplasm to the nucleus is necessary for cell division, but not sufficient, as its inhibitors do not allow the cell to enter mitosis prematurely. In addition to the back up inhibition of the cyclin B-Cdk1 complex, premature cellular division is prevented by the translocation of the cyclin B itself. The cyclin B-Cdk1 complex will remain in the cytoplasm in cells with DNA damage, rather than translocate to the nucleus, keeping the cell inhibiting the cell from entering mitosis.

neg: Clone (cell biology) cells cannot divide indefinitely as after a few cycles of cell division the cells stop expressing an enzyme telomerase. The genetic material, in the form of deoxyribonucleic acid (DNA), continues to shorten with each cell division, and cells eventually stop dividing when they sense that their DNA is critically shortened. However, this enzyme in "youthful" cells replaces these lost bits (nucleotides) of DNA, thus making almost unlimited cycles of cell division possible. It is believed that the above-mentioned tissues have a constitutional elevated expression of telomerase. When ultimately many cells are produced by a single cell, "clonal expansion" is said

neg: Meiomitosis Meiomitosis In cell biology, Meiomitosis is an aberrant cellular division pathway through which daughter cells following mitosis inherit partially expressed meiotic machinery. During normal mitosis, sister chromatids separate into two identical daughter cells. In meiosis is a diploid cell (2N) duplicates its DNA once and undergoes two rounds of cell division to produce four haploid (1N), germ cells that promotes the recombination of large expanses of chromosomal DNA, potentially similar in size to those lost or gained in cancer. In meiotic division, homologous chromosomes are held together by cohesions, and after resolution of chiasma (the recombination crossover points with the

neg: Survivin proteins called IAPs plays a role in regulating cell death by inhibiting the process. IAPs like survivin, inhibit apoptosis by physically binding to and inhibiting proper caspase function. The function of IAPs is evolutionarily conserved as Drosophila homologues of IAPs have been shown to be essential for cell survival. IAPs have been implicated in studies to have a regulatory effect on cell division. Yeast cells with knock-outs of certain IAP genes did not show problems associated with cell death, but showed defects in mitosis characterized by improper chromosome segregation or failed cytokinesis. Deletion of particular IAPs does not seem to