Name: cell cycle stages in mitosis
Uploaded: 2019-03-11T09:21:14.000Z
Duration: 2 min 3 s
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K12 Standards

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North Carolina K-12 Science Standard Course of Study

9-12

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms- Structures and Processes

LS.Bio.2.1

Mitosis and Cytokinesis

<p>Composta de cinco fases únicas a mitose é uma forma de divisão onde o material genético de uma célula é particionado entre duas células filhas. Primeiro, durante prófase em humanos a cromatina nucleica se condensa em cromossomos em forma de x composto por pares de cromatídeas irmãs anexadas as junções dos centrómeros. Simultaneamente, fora do núcleo, duas organelas em forma de L, chamadas centrossomas migram para lados opostos de célula.</p><p>Ao fazê-lo filamentos de microtúbulos começam a crescer em cada um, ou em direção ao interior ou exterior da célula para formar um aparelho de fuso semelhante a uma teia. Em seguida, o envelope nuclear dissolve-se durante a prometáfase expondo os cromossomos a outros conteúdos da célula. Estruturas proteicas também aparecem em ambos os lados dos centrómeros, uma para cada cromatídeo.</p><p>Uma vez que estes cinetócoros se formam os microtúbulos interiores presos a eles são estendidos com cada cromatídea-irmã sendo amarrada em um polo diferente da célula. Assim, a mitose progride para a metáfase onde o aparelho de fuso reorganiza os cromossomos de modo a estarem igualmente orientados numa linha fixa ao longo do equador da célula. Com a anáfase, os cinetócoros fixos encurtam os microtúbulos e as cromatídeas-irmãs, agora individualmente referenciadas como cromossomas, são separados.</p><p>Estas e outras dinâmicas do microtúbulo também alongam a célula. Finalmente, os cromossomas aterram em lados opostos da célula durante a telófase, onde o aparelho de fuso se desintegra. O material genético se solta e dois envelopes nucleares, um ao redor de cada conjunto de cromossomas, surge.</p><p>Durante a telófase, em um processo distinto denominado citocinese, a célula é dividida citoplasmicamente. Assim, o resultado final da mitose é um par de células geneticamente idêntico ao seu precursor.</p>

<p>Guertin, David A., Susanne Trautmann e Dannel McCollum. "Citocinese em eucariotos." <em>Microbiol. Mol. Biol. Rev.</em> 66, nº 2 (1º de junho de 2002): 155–78. [<a href="https://doi.org/10.1128/MMBR.66.2.155-178.2002" target="__blank">Fonte</a>]</p>

mitose e citocinese

<p>Nas células eucarióticas, o ciclo da célula—o ciclo de divisão—é dividido em processos celulares distintos e coordenados que incluem crescimento celular, replicação de DNA/duplicação de cromossomas, distribuição de cromossomas pelas células filhas e, por fim, divisão celular. O ciclo celular é fortemente regulado pelos seus sistemas de controlo, bem como por sinais extracelulares que afetam a proliferação celular.</p>
 
 <p>Os processos do ciclo celular ocorrem ao longo de aproximadamente 24 horas (em células humanas típicas) e em duas grandes fases distintas. A primeira fase é a replicação de DNA, durante a fase S da interfase. A segunda fase é a fase mitótica (M), que envolve a separação dos cromossomas duplicados em dois novos núcleos (mitose) e divisão citoplasmática (citocinese). As duas fases estão separadas por intervalos (intervalos G<sub>1</sub> e G<sub>2</sub>), durante os quais a célula se prepara para a replicação e divisão.</p>
 
 <h4>O Processo da Mitose</h4>
 
 <p>A mitose pode ser dividida em cinco fases distintas—profase, prometafase, metafase, anafase e telofase. A citocinese, que começa durante a anafase ou telofase (dependendo da célula), faz parte da fase M, mas não faz parte da mitose.</p>
 
 <h4>Profase</h4>
 
 <p>À medida que a célula entra em mitose, os seus cromossomas replicados começam a condensar e tornam-se visíveis como estruturas filiformes com o auxílio de proteínas conhecidas como condensinas. O aparelho do fuso mitótico começa a formar-se entre os centrossomas—que foram duplicados durante a fase S—e migra para pólos opostos da célula. O fuso é composto por estruturas filamentosas chamadas microtúbulos que são compostos por monómeros da proteína tubulina. Microtúbulos do fuso começam a estender-se em direção aos cromossomas condensados. O nucléolo, um componente do núcleo que produz ribossomas, desaparece, indicando a iminente quebra do núcleo.</p>
 
 <h4>Prometafase</h4>
 
 <p>Durante a prometafase, os filamentos de microtúbulos do aparelho do fuso continuam a crescer, e os cromossomas terminam a condensação. O envelope nuclear quebra completamente, libertando os cromossomas. Alguns dos microtúbulos ligam-se aos cromossomas libertados, ligando-se a uma estrutura proteica chamada cinetocoro que está presente no centrómero de cada par de cromatídeos irmãos. Microtúbulos do fuso de pólos opostos prendem-se aos cinetocoros e capturam os pares de cromatídeos irmão condensados. Microtúbulos do fuso que não se prendem a cromossomas—microtúbulos polares e astrais—ajudam a separar os fusos e a ancorar os pólos do fuso à membrana celular.</p>
 
 <h4>Metafase</h4>
 
 <p>Os microtúbulos do fuso alinham cada par de cromatídeos irmãos totalmente condensados ao longo do equador da célula—na placa da metafase. A célula está pronta para se dividir.</p>
 
 <h4>Anafase</h4>
 
 <p>Os microtúbulos do fuso de pólos opostos, que estão ligados à estrutura do cinetocoro, encurtam e separam os cromatídeos irmãos pelo centrómero. As proteínas de coesão que mantêm os cromatídeos juntos agora quebram. Os microtúbulos do cinetocoro ao encurtar fazem com que cada cromatídeo do par—agora chamados cromossomas—migre para um pólo oposto.</p>
 
 <h4>Telofase</h4>
 
 <p>Assim que os cromossomas atingem pólos opostos da célula, eles descondensam e desenrolam para formar cromatina. Os filamentos de microtúbulos do fuso despolimerizam nos seus monómeros de tubulina, que são então usados como elementos do citoesqueleto em células filhas. Envelopes nucleares voltam a formar-se em volta de cada conjunto de cromossomas.</p>
 
 <h4>Citocinese</h4>
 
 <p>Durante a citocinese em células animais, filamentos de actina formam um anel contráctil na membrana plasmática para criar um sulco de decote, que eventualmente separa a célula em duas. Nas células vegetais, vesículas do aparelho de Golgi que transportam glicose, enzimas e proteínas estruturais unem-se para formar uma nova placa celular na localização da antiga placa metafásica. A placa celular em crescimento funde-se com as membranas plasmáticas de cada lado, eventualmente formando uma nova parede celular que divide a célula em duas.</p>
 
 <p>A mitose está completa, gerando duas células filhas idênticas à célula mãe. Na maioria das células humanas, a mitose é responsável por cerca de uma hora do ciclo celular de aproximadamente 24 horas.</p>

Mitose e Citocinese

Nos eucariotos, o ciclo de divisão celular é dividido em processos celulares distintos e coordenados que incluem crescimento celular, replicação de DNA / cromossomo ...

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Cell Cycle and Division

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cell cycle stages in mitosis

<p class="jove_content">Cell cycle stages in mitosis show how a eukaryotic cell copies its DNA and then divides into two daughter cells. The cycle is controlled by regulatory systems and by outside signals that affect cell growth and division. In typical human cells, the full cycle takes about 24 hours and includes two major phases. The first is DNA replication during the S phase of interphase. The second is the mitotic, or M, phase, which includes mitosis and cytokinesis. G1 and G2 are the gap stages between these phases, and they give the cell time to prepare for replication and division.</p>

<p class="jove_content">Mitosis has five stages: prophase, prometaphase, metaphase, anaphase, and telophase. Cytokinesis may begin during anaphase or telophase, depending on the cell, and it is part of the M phase but not part of mitosis. As mitosis begins in prophase, the replicated chromosomes condense and become visible with the help of condensin proteins. The spindle apparatus starts to form between the duplicated centrosomes, which move to opposite poles. This spindle is made of microtubules, which are built from tubulin proteins, and the nucleolus disappears as the nucleus prepares to break down.</p>

<p class="jove_content">During prometaphase, the chromosomes finish condensing and the nuclear envelope breaks down. This releases the chromosomes into the cell. Some spindle microtubules attach to kinetochores, which are protein structures on the centromere of each pair of sister chromatids. Microtubules from opposite poles capture the sister chromatid pairs. Other microtubules, called polar and astral microtubules, help push the spindle poles apart and anchor them to the cell membrane.</p>

<p class="jove_content">In metaphase, the spindle microtubules line up each pair of fully condensed sister chromatids at the equator of the cell. This position is called the metaphase plate. The cell is then ready to divide. In anaphase, the kinetochore microtubules shorten and pull the sister chromatids apart at the centromere. The cohesion proteins that hold the chromatids together break down. Each chromatid is now a chromosome, and it moves toward an opposite pole.</p>

<p class="jove_content">In telophase, the chromosomes reach the poles and begin to decondense into chromatin. The spindle microtubules also depolymerize into tubulin monomers, which can be used again as cytoskeletal elements in the daughter cells. New nuclear envelopes form around each set of chromosomes. Cytokinesis then divides the cytoplasm. In animal cells, actin filaments form a contractile ring in the plasma membrane and create a cleavage furrow that pinches the cell in two. In plant cells, Golgi vesicles carrying glucose, enzymes, and structural proteins join to form a cell plate at the former metaphase plate. The cell plate fuses with the plasma membranes on both sides and develops into a new cell wall. Mitosis is complete, and the result is two daughter cells identical to the parent cell. In most human cells, mitosis takes about one hour of the 24-hour cell cycle.</p>

Cell Cycle Stages in Mitosis

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Cell cycle stages in mitosis show how a eukaryotic cell copies its DNA and then divides into two daughter cells. The cycle is controlled by regulatory systems and by outside signals that affect cell growth and division. In typical human cells, the full cycle takes about 24 hours and includes two major phases. The first is DNA replication during the S phase of interphase. The second is the mitotic, or M, phase, which includes mitosis and cytokinesis. G1 and G2 are the gap stages between these...

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Learn how the cell cycle leads to mitosis and cytokinesis, from DNA replication and spindle formation to chromosome separation and cell division.

Cell Cycle Stages in Mitosis | JoVE K12

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A coleção JoVE Core dá vida à biologia através de mais de 300 vídeos de animação concisos e fáceis de entender que explicam conceitos-chave de biologia, além de mais de 150 vídeos de Cientistas em ação que mostram experimentos reais em pesquisa realizados nos laboratórios atualmente.

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Cell Cycle Stages in Mitosis

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