Name: chromatid pulling in cell division
Uploaded: 2023-04-30T18:28:50.000Z
Duration: 2 min 17 s
Channel: JoVE

K12 Standards

Pennsylvania State Academic Standards

9-12

Life Science

Inheritance and Variation of Traits

3.1.9-12.D

Separation of Sister Chromatids

Am Ende der Metaphase richten sich die bi-orientierten Chromosomen an der Metaphasenplatte aus. In dieser Phase halten die Kohäsin-Protein-Ringkomplexe die Schwesterchromatiden im Zentromerbereich zusammen und verhindern, dass sie auseinandergezogen werden.
Die Progression von Metaphase zu Anaphase wird durch die Cyclin-Cdk-induzierte Phosphorylierung eines Ubiquitin-Ligase-Enzyms mit mehreren Untereinheiten ausgelöst – des Anaphase-fördernden Komplexes, der auch als Zyklosom oder APC/C bekannt ist. Phosphoryliertes APC/C bindet an ein Protein, Cdc20, und bildet einen aktiven Komplex.
Der aktive APC/C-Komplex erkennt ein hemmendes Protein namens Securin, das an ein Proteaseenzym namens Separase gebunden ist. Vor dieser Erkennung hemmt Securin die Aktivität von Separase.
Der aktive APC/C-Komplex markiert Securin mit dem Protein Ubiquitin und zielt auf dessen proteasomalen Abbau ab. Durch die Zerstörung von Securin wird Separese freigesetzt.
Der Cyclin-Cdk-Komplex reguliert auch die ungebundene Separaseaktivität durch inhibitorische Phosphorylierung negativ.
Der aktive APC/C-Komplex bewirkt die Ubiquitinierung von Cyclinen und zielt auf deren proteasomalen Abbau ab. Durch die Zerstörung von Cyclin wird die enzymatische Aktivität von Cyclin-abhängigen Kinasen oder Cdks beseitigt.
Die Inaktivierung von Cdks ermöglicht es Phosphatase-Enzymen, Separase zu dephosphorylieren und verhindert die Cdk-vermittelte inhibitorische Rephosphorylierung von Separase. Die Dephosphorylierung ermöglicht es dem Separase-Enzym, den Cohesin-Ring-Komplex zu spalten, der die Schwesterchromatiden zusammenhält.
Die Kohäsinspaltung führt zu einem absoluten Verlust der Schwesterchromatiden-Kohäsion, was den Übergang von der Metaphase zur Anaphase markiert. Der Verlust der Kohäsion ermöglicht es den Schwesterchromatiden, sich zu trennen und sich zu entgegengesetzten Polen der Spindel zu bewegen.

<ol>
	<li>Claire Acquaviva und Jonathon Pines. 20016. "Der Anaphase-fördernde Komplex/Zyklosom: APC/C". Zeitschrift für Zellwissenschaft. 119: 2401-2404. [<a href="https://jcs.biologists.org/content/119/12/2401#sec-2">Quelltext</a>]</li>
	<li>Frank Uhlmann, Friedrich Lottspeich und Kim Nasmyth. 1999. "Die Schwester-Chromatiden-Trennung zu Beginn der Anaphase wird durch die Spaltung der Kohäsin-Untereinheit Scc1 gefördert." Nature 400 (6739). Nature Publishing Group: 37–42. [<a href="https://mcb.berkeley.edu/courses/mcb230/WEB/PAPERS/SCC1.pdf">Quelltext</a>]</li>
	<li>Farr, Katie A. und Orna Cohen-Fix. "Der Übergang von der Metaphase zur Anaphase: ein Fall von produktiver Zerstörung." Europäische Zeitschrift für Biochemie 263, Nr. 1 (1999): 14-19.</li>
	<li>Fang, Guowei, Hongtao Yu und W. Kirschner. "Kontrolle mitotischer Übergänge durch den anaphasenfördernden Komplex." Philosophische Transaktionen der Royal Society of London. Reihe B: Biological Sciences 354, Nr. 1389 (1999): 1583-1590.</li>
</ol>

abtrennung der schwesterchromatiden

Beim Übergang von der Prophase zur Metaphase verringert sich die Kohäsion entlang der chromosomalen Arme, was zur Auflösung der Schwesterchromatiden führt. Es verbleiben jedoch residuelle Kohäsinkontakte, die die Schwesterchromatiden zusammenhalten, bis der Übergang von der Metaphase zur Anaphase erfolgt. Diese residuale Verbindung verhindert eine vorzeitige Trennung der Schwesterchromatiden und blockiert damit das Risiko einer Aneuploidie in den Tochterzellen.

Mit dem Beginn der Anaphase wird Separase, ein proteolytisches Enzym, aktiviert. Die aktivierte Separase spaltet die Scc1-Untereinheit der residualen Kohäsinringe, was zu einem totalen Verlust der Kohäsion führt. Die Schwesterchromatiden trennen sich in Abwesenheit einer Kraft, die sie zusammenhält. Das Fehlen von Kohäsion erlaubt es den polwärts gerichteten Kräften, die entlang der Mikrotubuli ziehen, die getrennten Chromatiden zu den Spindelpolen zu ziehen.

In der frühen Mitose verhindert der Spindel-Assemblierungs-Checkpoint (SAC) die Ubiquitinierung von Proteinen durch den anaphasefördernden Komplex oder Cyclosom (APC/C), wie Securin und M-Phase-Cycline, deren Abbau für die Anaphase notwendig ist. Erst wenn jedes Chromosom korrekt auf dem mitotischen Spindel ausgerichtet ist, wird der SAC deaktiviert, um die Phosphorylierung und Aktivierung der regulatorischen Untereinheiten des APC/C – CDC20 und CDH1 – zu ermöglichen.

CDC20 wird durch Cdk1/Cyclin B phosphoryliert, um aktives APC/C-CDC20 zu bilden. Aktives APC/C-CDC20 katalysiert dann den Abbau von Securin, Cyclin A und Cyclin B, um den Übergang zur Anaphase zu fördern. Da die Cdk-Aktivität cyclinabhängig ist, führt der Abbau von Cyclin B zum Verlust der Cdk1-Aktivität. Der Verlust des Cdk1/Cyclin B-Komplexes deaktiviert APC/C-CDC20, aber aktiviert eine andere regulatorische Untereinheit, APC/C-CDH1, die das Ende der Metaphase-Anaphase-Transition signalisiert. Das aktive APC/C-CDH1 erleichtert den Austritt aus der Mitose und stabilisiert die anschließende G1-Phase, indem es die vorzeitige Anhäufung von mitotischen Cyclinen verhindert.

Der Wechsel in den Aktivitäten von APC/C-CDC20 und APC/C-CDH1 hat zwei bedeutende Konsequenzen. Erstens lösen diese regulatorischen Untereinheiten überlappende, aber unterschiedliche Substratspezifitäten aus und fördern dadurch einen geordneten Zellzyklusübergang. Zweitens werden CDC20 und CDH1 durch unterschiedliche Mechanismen reguliert. Wenn APC/C-CDC20 aktiv ist, erfährt CDH1 eine hemmende Phosphorylierung durch Cyclin B/Cdk1, was dessen Bindung an APC/C verhindert. Im Gegensatz dazu wird die Aktivität von CDC20 durch einen mitotischen Kontrollkomplex – einen multiproteinaktivierten Komplex (BUBR1, BUB3, CDC20 und MAD2) – gehemmt, der vom SAC aktiviert wird.

Abtrennung der Schwesterchromatiden

Beim Übergang von der Prophase zur Metaphase kommt es zu einer Verringerung der Kohäsion entlang der Chromosomenarme, was zur Auflösung der Schwester ...

Education

Lehre

JoVE Core

Cell Biology

Zellbiologie

Unit 1

Einheit 1

Cell Division

Zellteilung

KEY TERMS AND CONCEPTS

KERNBEGRIFFE UND KONZEPTE

chromatid pulling in cell division

Separation of sister chromatids is a key step in cell division. Sister chromatids are two identical copies of a chromosome that stay attached until the cell is ready to split them apart. Their separation helps each new cell receive the correct genetic material.

During this stage, the sister chromatids are pulled to opposite sides of the cell. This movement happens as the cell prepares to divide into two daughter cells. Once the chromatids separate, each side of the cell has a complete set of chromosomes.

This process is essential for accurate chromosome distribution. If sister chromatids do not separate properly, the new cells may not get the right genetic information. Understanding this step helps explain how cells copy and pass on DNA during division.

Chromatid Pulling in Cell Division

mitosis and cytokinesis

Stages of Cell Division in Eukaryotes

Cell division in eukaryotes follows a tightly regulated cycle that includes cell growth, DNA replication, chromosome duplication, chromosome distribution to daughter cells, and cell division. Regulatory systems and extracellular signals help control when cells divide. In typical human cells, the cycle takes about 24 hours. The cycle has two major stages. DNA is copied during the S phase of interphase. The mitotic, or M, phase then separates the duplicated chromosomes into two new nuclei and...

chromosome duplication

Chromosome Copying in Cell Division

Chromosome copying is an important step in cell division. Before a cell divides, it must make an exact copy of its chromosomes so each new cell can receive the same genetic information. A chromosome is a DNA-containing structure that carries genes. During duplication, the chromosome is copied into two identical sister chromatids. These copies stay attached until the cell is ready to separate them. This process helps ensure that daughter cells inherit a complete set of chromosomes. Accurate...

cohesins

Cohesins in Sister Chromatid Separation

Cohesins are protein complexes that help hold sister chromatids together after DNA is copied. They play a key role in cell division by keeping the two copies of a chromosome connected until the right time. These proteins act like a link between the sister chromatids. When the cell is ready to separate them, cohesins must be removed or released so each new cell can get one complete set of chromosomes. Cohesins are an important part of chromosome behavior during mitosis and meiosis. Their...

condensins

Condensin Proteins in Chromosome Packing

Condensin proteins help pack DNA into condensed chromosomes during cell division. They are part of the larger set of proteins that organize genetic material so it can be separated correctly when a cell divides. These proteins act by shaping and tightening chromosome structure. This process is important because DNA must be compacted before it can move through the stages of division. Condensins are therefore closely linked to chromosome condensation, the step that makes chromosomes more compact...

the mitotic spindle

How the Mitotic Spindle Guides Cell Division

The mitotic spindle guides chromosome movement during cell division. It is a structure made of microtubules, which are thin protein fibers in the cell. These fibers organize and help separate the genetic material before the cell splits. The spindle forms as the cell prepares to divide. Its fibers attach to chromosomes and line them up so they can be moved apart in an orderly way. This careful organization helps each new cell receive the correct set of chromosomes. The mitotic spindle is a key...

centrosome duplication

Centrosome Duplication in Cell Division

Centrosome duplication is an important step in cell division. The centrosome helps organize the cell’s internal structure, and it must be copied before a cell divides.

spindle assembly

Spindle Formation in Cell Division

Spindle formation in cell division is the process that builds the microtubule-based spindle needed to separate chromosomes. Microtubules are long protein fibers that help move and organize cell parts during division. During this process, microtubules grow and are arranged into a spindle structure around the chromosomes. The spindle forms in a way that supports chromosome movement to opposite sides of the cell. This step is essential for accurate cell division. Spindle formation depends on the...

attachment of sister chromatids

Sister Chromatid Attachment in Mitosis

Sister chromatid attachment in mitosis helps align duplicated chromosomes before they separate. Sister chromatids are the matching copies made after DNA replication. They stay connected until the cell is ready to divide. The attachment step is closely tied to the metaphase plate, the middle of the cell where chromosomes line up. This alignment helps each new cell receive one copy of every chromosome. Proper attachment is an important part of accurate cell division.

forces acting on chromosomes

Chromosome Movement During Cell Division

Chromosome movement during cell division depends on forces that act on the chromosomes. These forces help move the chromosomes into the right position as the cell divides. The transcript focuses on how these forces affect chromosome behavior during division. It highlights the role of the mitotic spindle, which is the structure that helps organize and move chromosomes. The spindle uses force to guide chromosome movement at the right time. Understanding these forces helps explain how...

separation of sister chromatids

Separation of sister chromatids is a key step in cell division. Sister chromatids are two identical copies of a chromosome that stay attached until the cell is ready to split them apart. Their separation helps each new cell receive the correct genetic material. During this stage, the sister chromatids are pulled to opposite sides of the cell. This movement happens as the cell prepares to divide into two daughter cells. Once the chromatids separate, each side of the cell has a complete set of...

the spindle assembly checkpoint

How Cells Verify Chromosome Spindle Attachment

The spindle assembly checkpoint helps cells verify that chromosomes are attached to the spindle before division continues. It acts as a safety step during cell division and helps prevent errors in chromosome separation. This checkpoint is controlled by kinetochores, which are protein structures on chromosomes that connect to spindle fibers. If a chromosome is not attached correctly, the checkpoint can delay progression until the problem is fixed. Once the attachment is correct, the cell can...

anaphase a and b

Chromosome and Spindle Movement in Anaphase

Anaphase is the stage of cell division when chromosomes move apart. In this phase, sister chromatids separate and travel toward opposite poles of the cell. Chromosome movement in anaphase can happen in two ways. In anaphase A, chromosomes move closer to the poles as the microtubules attached to them shorten. In anaphase B, the spindle poles themselves move farther apart and help stretch the cell. These two movements work together to ensure that the separated chromosomes are pulled to opposite...

anaphase promoting complex

Cell Cycle Control by APC

The anaphase-promoting complex, or APC, helps control cell cycle progression. It acts during cell division to help move the process from one stage to the next. This control is important for proper timing in the cell cycle. APC is a protein complex that works as a regulator. It helps trigger key steps that allow division to continue in an ordered way. By guiding this transition, APC supports normal cell cycle control.

the contractile ring

Cell Division and the Contractile Ring

The contractile ring helps cells divide at the end of cell division. It forms at the cell's center and tightens to split one cell into two. This process is part of cytokinesis, the stage when the cytoplasm divides. The ring is made of actin and myosin, two proteins that can work together to create force. As the ring contracts, it draws the cell membrane inward. This pinch helps separate the two daughter cells. Understanding the contractile ring is important for studying how cells complete...

determining the plane of cell division

Spindle Position and Cell Division Plane

The plane of cell division is set by the position of the spindle during mitosis. Cells use this internal structure to help decide where the cell will split. The result affects how the two daughter cells are arranged after division. This process is important in many developing tissues. It helps explain how cells divide in a controlled direction. A clear plane of division supports proper cell organization as new cells form. The transcript focuses on how the spindle is used to determine that...

the phragmoplast

Phragmoplast in Plant Cell Division

The phragmoplast is a plant cell structure that forms during cell division. It helps guide the final stage of division, when the cell begins to split into two daughter cells. In plant cells, the phragmoplast appears between the two new nuclei. It is part of the process that leads to the formation of a new cell wall. This wall separates the daughter cells after division is complete. The phragmoplast plays an important role in plant cytokinesis, which is the physical division of the cytoplasm.

distribution of cytoplasmic content

Cytoplasmic Content During Cell Division

Cytoplasmic content is distributed as a cell divides. This process helps each new cell receive the materials it needs to function. The cytoplasm includes the fluid and structures inside the cell membrane, but outside the nucleus. During cell division, this content is separated between the two daughter cells. The division must be organized so both cells can continue normal activity after the split. The video focuses on how this distribution occurs as part of cell division. It highlights the...

key terms and concepts

Learn how sister chromatids separate during cell division and move to opposite sides of the cell so daughter cells receive the correct genetic material.

Chromatid Pulling in Cell Division | JoVE K12

cell biology

JoVE Core Zellbiologie veranschaulicht komplexe zelluläre Prozesse in leicht verständlichen und dennoch umfassenden animierten Videolektionen. Diese Sammlung konzentriert sich auf die wesentlichen Bestandteile und Funktionen von Zellen, einschließlich Organellen und Membranen, Zelltransport und Zellenergie. Ergänzt wird sie durch Videos von Wissenschaftlern in Aktion, die die Anwendung der Zellbiologie in realen Forschungsexperimenten demonstrieren.

Louisiana Student Standards for Science

High School

Life Sciences

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

From Molecules To Organisms: Structures And Processes

HS-LS1-4

Tennessee Academic Standards

Biology

From Molecules to Organisms: Structures and Processes

BIO1.LS1.6

Minnesota Academic Standards in Science

3.1.1 9L.3.1.1.2

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

Arizona Science Standards

HS+B.L1

HS+B.L1U1.9

Alabama Course of Study Science

9-12.B.1.3

Florida Department of Education

SC.912.L.16

SC.912.L.16.14

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

B-LS1-4.

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Interphase

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Cohesins

Condensins

The Mitotic Spindle

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Attachment of Sister Chromatids

Forces Acting on Chromosomes

The Spindle Assembly Checkpoint

Anaphase A and B

Anaphase Promoting Complex

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Determining the Plane of Cell Division

The Phragmoplast

Distribution of Cytoplasmic Content

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DNA Packaging

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Organization of Genes

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3.1.9-12.P

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Genomic DNA in Eukaryotes

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What is Meiosis?

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3.1.9-12.Q

Chromatid Pulling in Cell Division

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