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

Alla fine della metafase, i cromosomi biorientati si allineano sulla piastra di metafase. Durante questa fase, i complessi ad anello proteici della coesina tengono insieme i cromatidi fratelli nella regione del centromero e impediscono loro di essere separati.
La progressione da metafase ad anafase è innescata dalla fosforilazione indotta da ciclina-Cdk di un enzima ubiquitina ligasi multisubunità, il complesso che promuove l'anafase, noto anche come ciclosoma o APC/C. L'APC/C fosforilato si lega a una proteina, Cdc20, formando un complesso attivo.
Il complesso attivo APC/C riconosce una proteina inibitoria chiamata securina che è legata a un enzima proteasi chiamato separasi. Prima di questo riconoscimento, la securina inibisce l'attività della separasi.
Il complesso attivo APC/C marcava la securina con la proteina ubiquitina, mirandola alla degradazione del proteasoma. La distruzione della securina rilascia la separasi.
Il complesso ciclina-Cdk regola negativamente anche l'attività della separasi non legata attraverso la fosforilazione inibitoria.
Il complesso attivo APC/C provoca l'ubiquitinazione delle cicline, mirandole alla degradazione proteasomiale. La distruzione della ciclina rimuove l'attività enzimatica delle chinasi ciclina-dipendenti o Cdk.
L'inattivazione di Cdks consente agli enzimi fosfatasi di defosforilare la separasi e previene la rifosforilazione inibitoria della separasi mediata da Cdk. La defosforilazione consente all'enzima separasi di scindere il complesso dell'anello di coesina che tiene insieme i cromatidi fratelli.
La scissione della coesina provoca la perdita assoluta della coesione dei cromatidi fratelli, segnando il passaggio dalla metafase all'anafase. La perdita di coesione permette ai cromatidi fratelli di separarsi e spostarsi ai poli opposti del fuso.

<ol>
	<li>Claire Acquaviva e Jonathon Pines. 20016. "Il complesso/ciclosoma che promuove l'anafase: APC/C". Giornale di scienza cellulare. 119: 2401-2404. [<a href="https://jcs.biologists.org/content/119/12/2401#sec-2">Sorgente</a>]</li>
	<li>Frank Uhlmann, Friedrich Lottspeich e Kim Nasmyth. 1999. "La separazione sorella-cromatide all'inizio dell'anafase è promossa dalla scissione della subunità della coesina Scc1." Natura 400 (6739). Gruppo editoriale Nature: 37–42. [<a href="https://mcb.berkeley.edu/courses/mcb230/WEB/PAPERS/SCC1.pdf">Sorgente</a>]</li>
	<li>Farr, Katie A. e Orna Cohen-Fix. "La transizione da metafase ad anafase: un caso di distruzione produttiva." European journal of biochemistry 263, n. 1 (1999): 14-19.</li>
	<li>Fang, Guowei, Hongtao Yu e W. Kirschner. "Controllo delle transizioni mitotiche da parte del complesso che promuove l'anafase". Transazioni filosofiche della Royal Society di Londra. Serie B: Scienze Biologiche 354, n. 1389 (1999): 1583-1590.</li>
</ol>

separazione dei cromatidi fratelli

Nel passaggio dalla profase alla metafase si verifica una riduzione della coesione lungo i bracci cromosomici, con conseguente risoluzione dei cromatidi fratelli. Tuttavia, rimangono connessioni di coesione residue per tenere insieme i cromatidi fratelli fino alla transizione dalla metafase all'anafase. La connessione residua impedisce qualsiasi separazione prematura dei cromatidi fratelli, bloccando i rischi di aneuploidia all'interno delle cellule figlie.

All'inizio dell'anafase viene attivata la separasi, un enzima proteolitico. La separasi attivata scinde la subunità Scc1 degli anelli di coesione residui, determinando una perdita totale di coesione. I cromatidi fratelli si separano in assenza di forza che li tenga insieme. La mancanza di coesione consente alle forze verso i poli, che tendono lungo i microtubuli, di trascinare i cromatidi separati verso i poli del fuso.

Nella mitosi iniziale, il punto di controllo dell'assemblaggio del fuso (SAC) impedisce al complesso di promozione dell'anafase o ciclosoma (APC/C) di proteine ubiquitinanti, come la securina e le cicline della fase M, la cui degradazione è necessaria per l'anafase. Solo quando ciascun cromosoma si allinea correttamente sul fuso mitotico, il SAC viene disattivato per consentire la fosforilazione e l'attivazione delle subunità regolatorie APC/C: CDC20 e CDH1.

Il CDC20 viene fosforilato da Cdk1/ciclina B per formare APC/C-CDC20 attivo. L'APC/C-CDC20 attivo catalizza quindi la degradazione della securina, della ciclina A e della ciclina B per promuovere la transizione anafase. Poiché l'attività di Cdk dipende dalla ciclina, la degradazione della ciclina B comporta la perdita dell'attività di Cdk1. La perdita del complesso Cdk1/ciclina B inattiva APC/C-CDC20 ma attiva un'altra subunità regolatoria, APC/C-CDH1, che segnala il completamento della transizione metafase-anafase. L'APC/C-CDH1 attivo facilita l'uscita mitotica e stabilizza la successiva fase G1 prevenendo l'accumulo prematuro di cicline mitotiche.

Lo scambio delle attività di APC/C-CDC20 e APC/C-CDH1 ha due conseguenze significative. Innanzitutto, queste subunità regolatorie innescano specificità di substrato sovrapposte ma distinte e quindi promuovono la transizione ordinata del ciclo cellulare. In secondo luogo, CDC20 e CDH1 sono regolati attraverso meccanismi diversi. Quando APC/C-CDC20 è attivo, CDH1 subisce fosforilazione inibitoria da parte della ciclina B/Cdk1, impedendole di legarsi ad APC/C. Al contrario, l'attività del CDC20 è inibita da un complesso di checkpoint mitotico, una multiproteina (BUBR1, BUB3, CDC20 e MAD2) attivata dal SAC.

Separazione dei cromatidi fratelli

Al passaggio dalla profase alla metafase, si verifica una riduzione della coesione lungo i bracci cromosomici, con conseguente risoluzione della sorella ...

Education

Didattica

JoVE Core

Cell Biology

Biologia cellulare

Unit 1

Unità 1

Cell Division

Divisione cellulare

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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 Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

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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The Cell Cycle Control System

Positive Regulator Molecules

Inhibition of CDK Activity

Mitosis and Cytokinesis

In eukaryotes, the cell division cycle is divided into distinct, coordinated cellular processes that include cell growth, DNA replication/chromosome ...

Chromosome Duplication

Cohesins

Condensins

The Mitotic Spindle

Centrosome Duplication

Spindle Assembly

Attachment of Sister Chromatids

Forces Acting on Chromosomes

The Spindle Assembly Checkpoint

Anaphase A and B

Anaphase Promoting Complex

The Contractile Ring

Determining the Plane of Cell Division

The Phragmoplast

Distribution of Cytoplasmic Content

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Fate Mapping

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Students who demonstrate understanding can use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.  Assessment Boundary: Assessment does not include specific gene control mechanisms or rote memorization of the steps of mitosis.

DNA Packaging

DNA as a Genetic Template

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Organization of Genes

Structure of a Gene

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Chromosome Structure

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Chromosome Replication

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The Nucleosome

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Chromatin Packaging

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Karyotyping

Proteins: From Genes to Degradation

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genome-size-and-the-evolution-of-new-genes

Genome Size and the Evolution of New Genes

Gene Families

Students who demonstrate understanding can ask questions to clarify relationships about the role of DNA and chromosomes in coding the instructions for characteristic traits passed from parents to offspring. Assessment Boundary: Assessment does not include the phases of meiosis or the biochemical mechanism of specific steps in the process.

3.1.9-12.P

Genomic DNA in Prokaryotes

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Binary Fission

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Genomic DNA in Eukaryotes

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What is Meiosis?

Meiosis is the process by which diploid cells divide to produce haploid daughter cells. In humans, each diploid cell contains 46 chromosomes, half from ...

Meiosis I

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Meiosis II

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Crossing Over

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Students who demonstrate understanding can make and defend a claim based on evidence that inheritable genetic variations may result from (1) new genetic combinations through meiosis, (2) viable errors occurring during replication, and/or (3) mutations caused by environmental factors. Assessment Boundary: Assessment does not include the phases of meiosis or the biochemical mechanism of specific steps in the process.

3.1.9-12.Q

Chromatid Pulling in Cell Division

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