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

בסוף המטאפאזה, הכרומוזומים הדו-כיווניים מתיישרים בצלחת המטאפאזה. במהלך שלב זה, קומפלקסים טבעתיים של חלבון הקוהסין מחזיקים את הכרומטידים האחיות יחד באזור הצנטרומר ומונעים מהם להתפרק.
התקדמות מטא-פאזה לאנאפאזה, מופעלת על-ידי זרחון המושרה על-ידי ציקלין-Cdk של אנזים רב-תת-יחידתי, יוביקוויטין ליגאז – קומפלקס מקדם אנאפאזה, הידוע גם בשם ציקלוזום או APC/C. APC/C פוספורילציה נקשר לחלבון, Cdc20, ויוצר קומפלקס פעיל.
קומפלקס APC/C הפעיל מזהה חלבון מעכב בשם סקורין הקשור לאנזים פרוטאז הנקרא separase. לפני הכרה זו, securin מעכב את הפעילות של separase.
קומפלקס APC/C הפעיל מתייג את סקורין עם החלבון יוביקוויטין, ומכוון אותו לפירוק פרוטאזומלי. הרס של securin משחרר הפרדה.
קומפלקס cyclin-Cdk גם מווסת באופן שלילי פעילות הפרדה בלתי קשורה באמצעות זרחן מעכב.
קומפלקס הנגמ"ש/C הפעיל גורם לאוביקוויטינציה של ציקלינים, ומכוון אותם לפירוק פרוטאזומלי. הרס הציקלין מסיר את הפעילות האנזימטית של קינאזות תלויות ציקלין או Cdks.
השבתה של Cdks מאפשרת לאנזימי פוספטאז לפרק את הפרדת הפוספורילט ומונעת זרחן מחדש של הפרדות בתיווך Cdk. דה-פוספורילציה מאפשרת לאנזים הפראז לבקע את קומפלקס טבעות הקוהסין המחזיק כרומטידים אחים יחד.
מחשוף הקוהסין גורם לאובדן מוחלט של לכידות אחות-כרומטית, ומסמן את המעבר ממטא-פאזה לאנאפאזה. אובדן הלכידות מאפשר לכרומטידים האחיות להיפרד ולעבור לקטבים מנוגדים של הציר.

<ol>
	<li>קלייר אקוויווה ויונתן פינס. 20016. "קומפלקס מקדם אנאפאזה/ציקלוזום: APC/C". כתב עת למדעי התא. 119: 2401-2404. [<a href="https://jcs.biologists.org/content/119/12/2401#sec-2">מקור</a>]</li>
	<li>פרנק אולמן, פרידריך לוטספייך וקים נאסמית'. 1999. "הפרדה אחות-כרומטידית בתחילת אנאפאזה מקודמת על ידי מחשוף של תת-יחידת הקוהסין Scc1." טבע 400 (6739). קבוצת הוצאת טבע: 37–42. [<a href="https://mcb.berkeley.edu/courses/mcb230/WEB/PAPERS/SCC1.pdf">מקור</a>]</li>
	<li>פאר, קטי א. ואורנה כהן-פיקס. "המעבר ממטאפאזות לאנאפאזה: מקרה של הרס פרודוקטיבי". כתב העת האירופי לביוכימיה 263, מס '1 (1999): 14-19.</li>
	<li>פאנג, גואווי, הונגטאו יו וו. קירשנר. "שליטה במעברים מיטוטיים על ידי קומפלקס מקדם אנאפאזה". עסקאות פילוסופיות של החברה המלכותית של לונדון. סדרה ב': מדעי הביולוגיה 354, מס' 1389 (1999): 1583-1590.</li>
</ol>

הפרדת כרומטידים אחיות

<div style="direction: rtl;">
במעבר מפרופזה למטאפאזה, יש הפחתה בלכידות לאורך הזרועות הכרומוזומליות, וכתוצאה מכך רזולוציה של כרומטידות אחיות. עם זאת, נשארים קשרי קוהזין שיוריים כדי להחזיק את הכרומטידות האחיות יחד עד המעבר ממטאפאזה לאנאפאזה. הקשר השיורי מונע כל הפרדה מוקדמת של כרומטידות אחיות, וחוסם את הסיכונים לאנאופלואידה בתוך תאי הבת.

עם תחילת האנפאזה מופעל ספראזה, אנזים פרוטאוליטי. הפרדה המופעלת מבקעת את תת-היחידה Scc1 של טבעות הקוהזין השיוריות, וכתוצאה מכך לאובדן מוחלט של לכידות. האחיות-כרומטידות נפרדות בהיעדרות של כוח שמהחזיקה אותן יחד. חוסר הלכידות מאפשר לכוחות הקוטב, המתאמצים לאורך המיקרוטובולים, למשוך את הכרומטידות המופרדות לכיוון מוטות הציר.

במיטוזה מוקדמת, נקודת המחסום להרכבת הציר (SAC) אוסרת על הקומפלקס או הציקלוזום (APC/C) המעודד אנפאזה להעלות חלבונים, כגון Securin ו-M-phase cyclins, שההתפרקות שלהם נחוצה לאנפאזה. רק כאשר כל כרומוזום מתיישר בצורה נכונה על הציר המיטוטי, ה-SAC מושבת כדי לאפשר זרחון והפעלה של תת-יחידות הרגולטוריות של APC/C- CDC20 ו-CDH1.

ה-CDC20 עובר זרחון על ידי Cdk1/cyclin B ליצירת APC/C-CDC20 פעיל. Active APC/C-CDC20 אז מזרז את הפירוק של Securin, cyclin A ו-cyclin B כדי לקדם מעבר אנאפאזה. מכיוון שפעילות Cdk תלויה בציקלין, פירוק ציקלין B מביא לאובדן פעילות Cdk1. אובדן קומפלקס Cdk1/cyclin B משבית את APC/C-CDC20 אך מפעיל תת-יחידה רגולטורית אחרת, APC/C-CDH1, המאותתת על השלמת המעבר מטאפאזה לאנאפאזה. ה-APC/C-CDH1 הפעיל מקל על יציאה מיטוטית ומייצב את שלב ה-G1 העוקב על ידי מניעת הצטברות מוקדמת של ציקלינים מיטוטיים.

למעבר בפעילויות של APC/C-CDC20 ו-APC/C-CDH1 יש השלכות משמעותיות משמעותיות. ראשית, תת-יחידות רגולטוריות אלו מעוררות סגוליות מצע חופפות אך ברורות ובכך מקדמות מעבר מסודר של מחזור תאים. שנית, CDC20 ו-CDH1 מוסדרים באמצעות מנגנונים שונים. כאשר APC/C-CDC20 פעיל, CDH1 עובר זרחון מעכב על ידי cyclin B/Cdk1, ומונע ממנו להיקשר ל-APC/C. לעומת זאת, פעילות ה-CDC20 מעוכבת על ידי קומפלקס מיטוטי מחסום - מולטי חלבון (BUBR1, BUB3, CDC20 ו-MAD2) המופעל על ידי ה-SAC.
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במעבר מפרופזה למטאפאזה, יש ירידה בלכידות לאורך הזרועות הכרומוזומליות, וכתוצאה מכך רזולוציה של אחות ...

Education

JoVE Core

Cell Biology

ביולוגיה של התא

Unit 1

יחידה 1

Cell Division

חלוקת תאים

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

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.

What is the Cell Cycle?

The cell cycle refers to the sequence of events occurring throughout a typical cell&#8217;s life. In eukaryotic cells, the somatic cell cycle has two ...

Interphase

The cell cycle occurs over approximately 24 hours (in a typical human cell) and in two distinct stages: interphase, which includes three phases of the ...

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

An Introduction to Cell Division

Cell division is the process by which a parent cell divides and gives rise to two or more daughter cells. It is a means of reproduction for single-cell ...

Cell Cycle Analysis

Cell cycle refers to the set of events through which a cell grows, replicates its genome, and ultimately divides into two daughter cells through the ...

Live Cell Imaging of Mitosis

Mitosis is a form of cell division in which a cell&#8217;s genetic material is divided equally between two daughter cells. Mitosis can be broken down into ...

Fertilization

During fertilization, an egg and sperm cell fuse to create a new diploid structure. In humans, the process occurs once the egg has been released from the ...

Cleavage and Blastulation

After a large-single-celled zygote is produced via fertilization, the process of cleavage occurs while zygotes travel through the uterine tube. Cleavage ...

Gastrulation

Gastrulation establishes the three primary tissues of an embryo: the ectoderm, mesoderm, and endoderm. This developmental process relies on a series of ...

Neurulation

Neurulation is the embryological process which forms the precursors of the central nervous system and occurs after gastrulation has established the three ...

Cell Migration

Cell migration, the process by which cells move from one location to another, is essential for the proper development and viability of organisms ...

an-introduction-to-developmental-genetics

An Introduction to Developmental Genetics

Development is the complex process through which a single-celled embryo transforms into a multicellular organism. Developmental processes are guided by ...

An Introduction to Organogenesis

Organogenesis is the process by which organs arise from one of three germ layers during the later stages of embryonic development. Researchers studying ...

Fate Mapping

Fate mapping is a technique used to understand how embryonic cells divide, differentiate, and migrate during development. In classic fate mapping ...

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

Two structural features of the DNA molecule provide a basis for the mechanisms of heredity: the four nucleotide bases and its double-stranded nature. The ...

Organization of Genes

Structure of a Gene

A gene is the fundamental unit of heredity. Every individual has two copies of each gene, one inherited from each parent. Although most people contain the ...

Chromosome Structure

A functional eukaryotic chromosome must contain three elements: a centromere, telomeres, and numerous origins of replication.
The centromere is a DNA ...

Chromosome Replication

Before a cell can divide, it must accurately replicate all of its chromosomes, including the DNA and its associated histone and non-histone ...

The Nucleosome

DNA in a human cell is almost 2m long and it is packed inside a tiny nucleus that is only a few microns in diameter. The level of compaction of DNA inside ...

The Nucleosome Core Particle

Nucleosomes are the DNA-histone complex, where the DNA strand is wound around the histone core. The histone core is an octamer containing two copies of ...

Nucleosome Remodeling

Nucleosomes are the basic units of chromatin compaction. Each nucleosome consists of the DNA bound tightly around a histone core, which makes the DNA ...

Chromatin Packaging

Each human somatic cell contains 6 billion base-pairs of DNA. Each base-pair is 0.34 nm long, which means that each diploid cell contains a staggering 2 ...

Karyotyping

Proteins: From Genes to Degradation

The DNA Helix

Deoxyribonucleic acid, or DNA, is the genetic material responsible for passing traits from generation to generation in all organisms and most viruses. DNA ...

The Central Dogma

The central dogma explains the flow of genetic information from DNA nucleotides to the amino acid sequence of proteins.
RNA is the Missing Link Between ...

Mutations

Mutations are changes in the sequence of DNA. These changes can occur spontaneously or they can be induced by exposure to environmental factors. Mutations ...

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

The genome of most prokaryotic organisms consists of double-stranded DNA organized into one circular chromosome in a region of cytoplasm called the ...

Binary Fission

Fission is the division of a single entity into two or more parts, which regenerate into separate entities that resemble the original. Organisms in the ...

Genomic DNA in Eukaryotes

Eukaryotes have large genomes compared to prokaryotes. To fit their genomes into a cell, eukaryotic DNA is packaged extraordinarily tightly inside the ...

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

Meiosis is a carefully orchestrated set of cell divisions, the goal of which&#x2014;in humans&#x2014;is to produce haploid sperm or eggs, each containing ...

Meiosis II

Meiosis II is the second and final stage of meiosis. It relies on the haploid cells produced during meiosis I, each of which contain only 23 ...

Crossing Over

Unlike mitosis, meiosis aims for genetic diversity in its creation of haploid gametes. Dividing germ cells first begin this process in prophase I, where ...

Nondisjunction

During meiosis, chromosomes occasionally separate improperly. This occurs due to failure of homologous chromosome separation during meiosis I or failed ...

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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