Name: cell division: mitosis and cytokinesis
Uploaded: 2023-06-23T15:38:45.000Z
Duration: 1 min 35 s
Channel: JoVE

La mitosis es una forma de división celular en la que el material genético de una célula se divide entre dos células hijas. 
En primer lugar, durante la profase, la cromatina nucleica se condensa en cromosomas en forma de x compuestos por pares de cromátidas hermanas unidas en uniones de centrómero.
Al mismo tiempo, los centrosomas migran a lados celulares opuestos. A medida que lo hacen, los bastones de microtúbulos comienzan a crecer de cada uno, formando un aparato de huso similar a una red.
A continuación, la envoltura nuclear se disuelve durante la prometafase y las estructuras proteicas, denominadas cinetocoros, aparecen a ambos lados de los centrómeros, una por cada cromatina.
Una vez que se forman estos cinetocoros, los microtúbulos interiores que se extienden se adhieren a ellos, y cada cromátida hermana está atada a un polo celular diferente.
En la metafase, el aparato fusiforme reorganiza los cromosomas para que estén orientados en una fila fija a lo largo del ecuador de la célula.
Con la anafase, los microtúbulos fijos del cinetocoro se acortan y las cromátidas hermanas se separan. Estas y otras dinámicas de microtúbulos también alargan la célula.
Durante la telofase, el aparato fusiforme se disuelve, las cromátidas se aflojan y las envolturas nucleares se reforman.
Finalmente, la célula se divide citoplasmáticamente por citocinesis, formando un par de células genéticamente idénticas a su precursora.

<ol>
	<li>Guertin, David A., Susanne Trautmann y Dannel McCollum. "Citocinesis en eucariotas". Microbiol. Mol. Biol. Rev. 66, no. 2 (1 de junio de 2002): 155–78.</li>
</ol>

mitosis y citocinesis

Mitosis And Cytokinesis

En las eucariotas, el ciclo de división celular se divide en procesos celulares distintos y coordinados que incluyen el crecimiento celular, la replicación del ADN/duplicación de los cromosomas, la distribución de los cromosomas a las células hijas y, finalmente, la división celular. El ciclo celular está estrechamente regulado por sus sistemas reguladores, así como por señales extracelulares que afectan la proliferación celular.

Los procesos del ciclo celular ocurren durante aproximadamente 24 horas (en células humanas típicas) y en dos etapas principales distinguibles. La primera etapa es la replicación del ADN, durante la fase S de la interfase. La segunda etapa es la fase mitótica (M), que implica la separación de los cromosomas duplicados en dos nuevos núcleos (mitosis) y la división citoplasmática (citocinesis). Las dos fases están separadas por intervalos (espacios G1 y G2), durante los cuales la célula se prepara para la replicación y la división.

El proceso de la mitosis

La mitosis se puede dividir en cinco etapas distintas: profase, prometafase, metafase, anafase y telofase. La citocinesis, que comienza durante la anafase o la telofase (según la célula), es parte de la fase M pero no de la mitosis.

Profase

A medida que la célula entra en mitosis, sus cromosomas replicados comienzan a condensarse y hacerse visibles como estructuras filiformes con la ayuda de proteínas conocidas como condensinas. El aparato del huso mitótico comienza a formarse entre los centrosomas (que se duplicaron durante la fase S) y migra a los polos opuestos de la célula. El huso está formado por estructuras filamentosas llamadas microtúbulos que se componen de monómeros de proteína tubulina. Los microtúbulos del huso comienzan a extenderse hacia los cromosomas condensados. El nucleolo, un componente del núcleo que produce ribosomas, desaparece, lo que indica la inminente ruptura del núcleo.

Prometafase

Durante la prometafase, los filamentos de microtúbulos del aparato del huso continúan creciendo y los cromosomas terminan de condensarse. La envoltura nuclear se rompe por completo, liberándose los cromosomas. Algunos de los microtúbulos se unen a los cromosomas liberados, uniéndose a una estructura proteica llamada cinetocoro que está presente en el centrómero de cada par de cromátidas hermanas. Los microtúbulos del huso de polos opuestos se unen a los cinetocoros y capturan los pares de cromátidas hermanas condensadas. Los microtúbulos del huso que no se unen a los cromosomas (microtúbulos polares y astrales) ayudan a separar los husos y a anclar los polos del huso a la membrana celular.

metafase

Los microtúbulos del huso alinean cada par de cromátidas hermanas completamente condensadas a lo largo del ecuador de la célula, en la placa metafásica. La célula ahora está lista para dividirse.

Anafase

Los microtúbulos de los polos opuestos del huso, que están unidos a la estructura del cinetocoro, acortan y separan las cromátidas hermanas en el centrómero. Las proteínas de cohesión que mantienen unidas las cromátidas ahora se descomponen. El acortamiento de los microtúbulos cinetocoros hace que cada cromátida del par (ahora llamada cromosomas) migre a un polo opuesto.

Telofase

Una vez que los cromosomas alcanzan los polos opuestos de la célula, se descondensan y se desenrollan para formar cromatina. Los filamentos de microtúbulos del huso se despolimerizan en sus monómeros de tubulina, que entonces se utilizan como elementos citoesqueléticos en las células hijas. Las envolturas nucleares se vuelven a ensamblar alrededor de cada conjunto de cromosomas.

Citocinesis

Durante la citocinesis en las células animales, los filamentos de actina forman un anillo contráctil en la membrana plasmática para crear un surco de escisión, que eventualmente divide la célula en dos. En las células vegetales, las vesículas del aparato de Golgi que transportan glucosa, enzimas y proteínas estructurales se unen para formar una nueva placa celular en el lugar de la antigua placa metafásica. La placa celular en crecimiento se fusiona con las membranas plasmáticas de cada lado, formando eventualmente una nueva pared celular que divide la célula en dos.

La mitosis ahora se completa y genera dos células hijas que son idénticas a la célula madre. En la mayoría de las células humanas, la mitosis representa aproximadamente una hora del ciclo celular de aproximadamente 24 horas.

Mitosis y citocinesis

En los eucariotas, el ciclo de división celular se divide en procesos celulares distintos y coordinados que incluyen el crecimiento celular, la replicación del ADN/cromosomas ...

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Essential Cellular Processes

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KEY TERMS AND CONCEPTS

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Cell division depends on mitosis and cytokinesis. Mitosis is the stage when the cell’s nucleus divides and the copied chromosomes are separated into two sets. Cytokinesis is the step that follows and splits the cell into two daughter cells.

These two processes work together to make sure each new cell receives genetic material and its own cytoplasm. Mitosis keeps the chromosome sets organized, while cytokinesis finishes the division of the whole cell. Together, they create two separate cells from one starting cell.

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Cell division depends on mitosis and cytokinesis. Mitosis is the stage when the cell’s nucleus divides and the copied chromosomes are separated into two sets. Cytokinesis is the step that follows and splits the cell into two daughter cells. These two processes work together to make sure each new cell receives genetic material and its own cytoplasm. Mitosis keeps the chromosome sets organized, while cytokinesis finishes the division of the whole cell. Together, they create two separate cells...

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key terms and concepts

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Cell Division: Mitosis and Cytokinesis | JoVE K12

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JoVE Core Anatomy and Physiology showcases the anatomical and physiological details of the human body in comprehensive, clear, and engaging video animations. This collection of lessons focuses on the structures, components, functions, and requirements of the human body. It is complemented by scientist-in-action videos that demonstrate the application of this knowledge in real-world medical and research settings.

Cell Division: Mitosis and Cytokinesis

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