Name: mitosis and cytokinesis stages
Uploaded: 2021-04-07T12:12:01.000Z
Duration: 2 min 3 s
Channel: JoVE

K12 Standards

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

9-12

Biology

Heredity

Cellular genetics

Mitosis and Cytokinesis

Mitoza, składająca się z pięciu unikalnych etapów, jest formą podziału, w której materiał genetyczny komórki jest podzielony między dwie komórki potomne.  Po pierwsze, podczas profazy u ludzi, chromatyna nukleinowa kondensuje się w chromosomy w kształcie litery X złożone z par chromatyd siostrzanych przyłączonych w połączeniach centromerowych.
Jednocześnie na zewnątrz jądra dwie organelle w kształcie litery L zwane centrosomami migrują na przeciwległe strony komórki. Gdy to robią, pręciki mikrotubul zaczynają rosnąć z każdego z nich, albo w kierunku wnętrza komórki, albo na zewnątrz, tworząc wrzeciono przypominające pajęczynę.
Następnie otoczka jądrowa rozpuszcza się podczas prometafazy, odsłaniając chromosomy przed inną zawartością komórki. Struktury białkowe pojawiają się również po obu stronach centromerów, po jednej dla każdej chromatyny.
Gdy te kinetochory się uformują, wydłużające się wewnętrzne mikrotubule przyczepiają się do nich, przy czym każda siostrzana chromatyda jest przywiązana do innego bieguna komórkowego.
Mitoza następnie przechodzi do metafazy, w której aparat wrzeciona przestawia chromosomy tak, aby były podobnie zorientowane w ustalonym rzędzie wzdłuż równika komórki.
W przypadku anafazy mikrotubule z utrwalonymi kinetochorami skracają się, a chromatydy siostrzane, obecnie indywidualnie określane jako chromosomy, są rozsuwane. Ta i inna dynamika mikrotubul również wydłuża komórkę.
Wreszcie chromosomy lądują po przeciwnych stronach komórki podczas telofazy, gdzie na wrzecionie aparat rozpada się. Materiał genetyczny rozluźnia się i powstają dwie otoczki jądrowe, po jednej wokół każdego zestawu chromosomów.
Podczas telofazy, w odrębnym procesie zwanym cytokinezą, komórka jest dzielona cytoplazmatycznie . Tak więc końcowym wynikiem mitozy jest para komórek genetycznie identyczna z ich prekursorem.

Guertin, David A., Susanne Trautmann i Dannel McCollum. "Cytokineza u eukariontów." Microbiol. Mol. Biol. Rev. 66, nr 2 (1 czerwca 2002): 155–78. [<a href="https://doi.org/10.1128/MMBR.66.2.155-178.2002" target="__blank">Źródło</a>]

mitoza i cytokineza

U eukariontów cykl podziału komórki jest podzielony na odrębne, skoordynowane procesy komórkowe, które obejmują wzrost komórek, replikację DNA/duplikację chromosomów, dystrybucję chromosomów do komórek potomnych i wreszcie podział komórki. Cykl komórkowy jest ściśle regulowany przez systemy regulacyjne, a także sygnały zewnątrzkomórkowe, które wpływają na proliferację komórek.

Procesy cyklu komórkowego zachodzą przez około 24 godziny (w typowych komórkach ludzkich) i składają się z dwóch głównych, dających się wyróżnić etapów. Pierwszym etapem jest replikacja DNA podczas fazy S interfazy. Drugi etap to faza mitotyczna (M), która polega na rozdzieleniu zduplikowanych chromosomów na dwa nowe jądra (mitoza) i podziale cytoplazmatycznym (cytokineza). Obie fazy oddzielają przerwy (przerwy G1 i G2), podczas których komórka przygotowuje się do replikacji i podziału.

<h4>Proces mitozy</h4>

Mitozę można podzielić na pięć odrębnych etapów — profazę, prometafazę, metafazę, anafazę i telofazę. Cytokineza, która rozpoczyna się podczas anafazy lub telofazy (w zależności od komórki), jest częścią fazy M, ale nie częścią mitozy.

<h4>Profaza</h4>

Gdy komórka wchodzi w mitozę, jej replikowane chromosomy zaczynają się kondensować i stają się widoczne jako nitkowate struktury za pomocą białek zwanych kondensynami. Aparat wrzeciona mitotycznego zaczyna tworzyć się pomiędzy centrosomami — które zostały zduplikowane w fazie S — i migruje do przeciwnych biegunów komórki. Wrzeciono składa się ze struktur nitkowatych zwanych mikrotubulami, które składają się z monomerów białka tubuliny. Mikrotubule wrzeciona zaczynają rozciągać się w kierunku skondensowanych chromosomów. Jąderko, składnik jądra wytwarzający rybosomy, zanika, wskazując na zbliżający się rozkład jądra.

<h4>Prometafaza</h4>

Podczas prometafazy włókna mikrotubul z aparatu wrzecionowego nadal rosną, a chromosomy kończą kondensację. Otoczka jądrowa ulega całkowitemu rozpadowi, uwalniając chromosomy. Niektóre mikrotubule przyczepiają się do uwolnionych chromosomów, wiążąc się ze strukturą białkową zwaną kinetochorem, która jest obecna na centromerze każdej pary chromatyd siostrzanych. Mikrotubule wrzecionowe z przeciwnych biegunów przyczepiają się do kinetochorów i wychwytują skondensowane pary chromatyd siostrzanych. Mikrotubule wrzeciona, które nie przyczepiają się do chromosomów — mikrotubule polarne i astralne — pomagają rozsuwać wrzeciona i zakotwiczyć ich bieguny w błonie komórkowej.

<h4>Metafaza</h4>

Mikrotubule wrzeciona ustawiają każdą parę w pełni skondensowanych chromatyd siostrzanych wzdłuż równika komórki — na płytce metafazowej. Komórka jest teraz gotowa do podziału.

<h4>Anafaza</h4>

Mikrotubule z przeciwległych biegunów wrzeciona, które są przymocowane do struktury kinetochoru, skracają i oddzielają chromatydy siostrzane w centromerze. Białka kohezyjne utrzymujące razem chromatydy ulegają teraz rozpadowi. Skrócenie mikrotubul kinetochorowych powoduje, że każda chromatyda z pary — obecnie nazywana chromosomami — migruje do przeciwnego bieguna.

<h4>Telofaza</h4>

Gdy chromosomy dotrą do przeciwnych biegunów komórki, ulegają dekondensacji i rozwinięciu, tworząc chromatynę. Włókna mikrotubul wrzeciona depolimeryzują do monomerów tubuliny, które są następnie wykorzystywane jako elementy cytoszkieletu w komórkach potomnych. Otoczki jądrowe ponownie łączą się wokół każdego zestawu chromosomów.

<h4>Cytokineza</h4>

Podczas cytokinezy w komórkach zwierzęcych włókna aktynowe tworzą kurczliwy pierścień w błonie komórkowej, tworząc bruzdę rozszczepiającą, która ostatecznie ściska komórkę na dwie części. W komórkach roślinnych pęcherzyki aparatu Golgiego przenoszące glukozę, enzymy i białka strukturalne łączą się, tworząc nową płytkę komórkową w miejscu poprzedniej płytki metafazowej. Rosnąca płytka komórkowa łączy się z błonami plazmatycznymi po obu stronach, ostatecznie tworząc nową ścianę komórkową, która dzieli komórkę na dwie części.

Mitoza jest teraz zakończona i powstają dwie komórki potomne, identyczne z komórką rodzicielską. W większości komórek ludzkich mitoza stanowi około jednej godziny z około 24-godzinnego cyklu komórkowego.

Mitoza i cytokineza

U eukariontów cykl podziału komórek jest podzielony na odrębne, skoordynowane procesy komórkowe, które obejmują wzrost komórek, replikację DNA / chromosom ...

Education

JoVE Core

Molecular Biology

Biologia molekularna

Unit 2

Jednostka 2

Cell Division

Podział komórki

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

mitosis and cytokinesis stages

Mitosis and cytokinesis are the two main steps of cell division. Mitosis is the process that divides the nucleus, while cytokinesis splits the rest of the cell.

During mitosis, the cell’s genetic material is separated into two sets. This helps form two new nuclei with the same genetic information. Cytokinesis then completes division by separating the cytoplasm, which creates two daughter cells.

These stages work together to make cell division possible in growing and repairing tissues. Understanding mitosis and cytokinesis helps explain how one cell becomes two.

Mitosis and Cytokinesis Stages

mitosis and cytokinesis

Mitosis and cytokinesis are the two main steps of cell division. Mitosis is the process that divides the nucleus, while cytokinesis splits the rest of the cell. During mitosis, the cell’s genetic material is separated into two sets. This helps form two new nuclei with the same genetic information. Cytokinesis then completes division by separating the cytoplasm, which creates two daughter cells. These stages work together to make cell division possible in growing and repairing tissues.

duplication of chromatin structure

Chromatin Rebuilding During DNA Replication

Chromatin rebuilding during DNA replication helps cells copy DNA and pass on chromosome structure to daughter cells. During cell division, the genome must be disrupted and then reassembled across the whole chromosome. This process allows chromatin to be inherited, rebuilt, and maintained in new cells. The basic unit of chromatin is the nucleosome. A nucleosome contains DNA wrapped around an octamer of histone proteins, with short linker DNA between neighboring nucleosomes. The histone proteins...

cohesins

Cohesins in Meiosis and Genetic Disorders

Cohesin protein complexes act like molecular glue that keeps sister chromatids together. They are important in both mitosis and meiosis. In mitosis, cohesin complexes are removed from chromosomes before anaphase begins. Meiosis has two rounds of chromosome separation. Meiosis I separates homologous chromosomes, while Meiosis II separates sister chromatids. This process produces four daughter cells. The Meiosis I cohesin complex is made of four subunits: Smc1, Smc3, Rec8, and Scc3. Rec8...

condensins

How Condensins Shape Mitotic Chromosomes

Condensins shape chromosomes during mitosis, the stage when a cell divides. These large protein complexes use ATP, the cell’s energy molecule, to help turn loose post-interphase DNA into compact, separate chromosomes. They organize and segregate chromosomal DNA so it can be passed on correctly. Plant and animal cells contain two condensin complexes: condensin I and condensin II. Each complex has five subunits. Two are SMC, or Structural Maintenance of Chromosomes, subunits. One is a kleisin...

the mitotic spindle

How the Mitotic Spindle Separates Chromosomes

The mitotic spindle is a microtubule-based structure that helps separate chromosomes during cell division. It forms in eukaryotic cells and moves sister chromatids to opposite ends of the parent cell. This leaves each new cell nucleus with the correct genetic material. A bipolar spindle has two poles, and that shape is important for chromosome segregation. In many animal cells, two centrosomes are present when mitosis begins. Each centrosome helps organize a circular set of microtubules at one...

centrosome duplication

Centrosome Duplication in the Cell Cycle

Centrosome duplication is a key part of the animal cell cycle. The centrosome is the main microtubule organizing center, or MTOC, in animal cells. It contains two cylindrical centrioles at its core. Each centriole has nine sets of three microtubules held together by proteins. The two centrioles sit at right angles and are surrounded by the pericentriolar matrix, or PCM, a shapeless protein cloud. Duplication starts early in the cell cycle so each daughter cell can receive a centrosome after...

microtubule instability

Microtubule Growth and Shrinkage

Microtubules are hollow, cylindrical filaments in the cell. They are about 25 nm wide and can range from 200 nm to 25 μm in length. Their main building blocks are GTP-bound tubulin subunits that form αβ-heterodimers, which then assemble into protofilaments. These protofilaments join by lateral bonds to create stable microtubule cylinders. Microtubules are highly dynamic because they repeatedly assemble and break down. They can even grow on one end while shrinking on the other at the same time.

spindle assembly

How the Mitotic Spindle Forms

The mitotic spindle forms through centrosome-mediated, chromatin-mediated, and microtubule-mediated pathways. These pathways often work at the same time. Together, they build a strong spindle apparatus for cell division. In most cells, centrosomes are the main sites where microtubules begin to grow. During the G2 to prophase transition, centrosomes mature and make more microtubules. The growing microtubules extend from both centrosomes, and their plus-ends search for chromosomes by attaching...

attachment of sister chromatids

Kinetochore-Microtubule Binding in Mitosis

Kinetochore-microtubule binding helps chromosomes line up and separate during mitosis. After the nuclear envelope breaks down, condensed chromosomes are exposed to the bipolar microtubules of the mitotic spindle. The kinetochore is a large, disc-shaped protein complex at the centromere region of each sister chromatid, and it serves as the microtubule binding site. Usually, the plus-end of a single microtubule inserts into the kinetochore. In some cases, a kinetochore first makes lateral...

forces acting on chromosomes

Chromosome Movement During Mitosis

Chromosome movement during mitosis depends on several small forces that act at different times and positions in the cell. In prometaphase, these forces help chromosomes move to the equatorial plane and line up at the metaphase plate. Because the forces change with location and stage, chromosome behavior also changes as mitosis continues. Microtubules and motor proteins create two main kinds of force on chromosomes: poleward force and anti-poleward force, also called polar-ejection force.

separation of sister chromatids

Anaphase Start and Chromatid Release

Anaphase starts when sister chromatids are released from one another and pulled toward opposite spindle poles. Before that happens, cohesion along the chromosomal arms is reduced from prophase to metaphase, which helps the sister chromatids resolve. A residual cohesin link still holds them together until the metaphase-to-anaphase transition. This leftover connection helps prevent early separation and reduces the risk of aneuploidy, or the wrong number of chromosomes, in daughter cells. At the...

the spindle assembly checkpoint

How Cells Safeguard Chromosome Separation

The spindle assembly checkpoint helps cells safeguard chromosome separation during anaphase. It acts as a molecular surveillance system. The checkpoint checks whether the steps needed for chromosome segregation are complete before the cell moves on. Many proteins work together to control this checkpoint. If mutations affect these proteins, a cell may enter anaphase too early. Chromosomes can then separate before the needed steps are finished. When this happens, the daughter cells may receive...

anaphase a and b

Chromatid Movement by Microtubule Forces

Chromatid movement during anaphase depends on microtubule forces at the spindle. Kinetochore microtubules grow from the spindle poles, and their plus ends attach to kinetochores on sister chromatids. The kinetochore protein complex Ndc80 makes low-affinity links with the microtubule plus end.

the contractile ring

How Cells Build the Contractile Ring

Contractile rings are built from microfilaments and help separate daughter cells during cytokinesis. This ring forms as the cell cycle moves forward, but the exact timing and coordination with other cell cycle events are still not fully understood. RhoA, a small GTPase in the Ras superfamily, controls contractile ring assembly and function. The inactive form of RhoA is bound to GDP. A guanine nucleotide exchange factor, or Rho-GEF, is located in the cortex region, where the next cell division...

determining the plane of cell division

How Cells Set the Division Plane

How cells set the division plane during cell division affects daughter cell size and, in many cases, cell fate. The plane of division is perpendicular to the plane of chromosome segregation. Different organisms use different cues to place it, based on their shape and needs. In animal cells, the cleavage furrow forms along the division plane from the cell cortex, the area just below the plasma membrane. The mitotic spindle is the main guide for this position. If the spindle axis changes, the...

the phragmoplast

How Plant Cells Build a New Wall

Plant cells build a new wall during cytokinesis with help from the phragmoplast. This plant structure forms from the central spindle and related cell parts as the cell finishes dividing. In animal cells, the comparable structure is the midbody, but in plants the phragmoplast expands outward to guide new wall formation. The mature phragmoplast has a donut-like shape. It has an outer leading region, a middle transition zone, and an inner lagging region. New microtubules are assembled...

distribution of cytoplasmic content

How Organelles Are Split During Cytokinesis

Cytokinesis splits a cell’s chromosomes and organelles into two daughter cells. Before cell division, organelles grow and divide. They cannot be made from scratch, so each daughter cell must inherit at least one copy to survive. Many details of this organelle sorting process are still not fully known. The cytoplasm contains organelles, salts, proteins, and water. Small organelles such as peroxisomes and lysosomes can be shared by simple diffusion. Because cells contain many copies of these...

anaphase promoting complex

APC Activates Chromosome Separation

The anaphase-promoting complex, or APC, helps control cell cycle progression by destroying specific proteins at the right time. These proteins are tagged with ubiquitin by ubiquitin ligases and then broken down by the proteasome. The SCF (Skp1/Cullin/F-box) complex and APC are two major ubiquitin ligases involved in this process. SCF stays active throughout the cell cycle, but APC turns on during the metaphase-to-anaphase transition. APC becomes active when Cdc20 or Cdh1 binds to it. These...

key terms and concepts

Learn how mitosis separates the nucleus and cytokinesis divides the cytoplasm to form two daughter cells. Clear high school cell division content.

Mitosis and Cytokinesis Stages | JoVE K12

molecular biology

JoVE Core Molecular Biology showcases the molecular processes of the cell through clear and concise animated video lessons. Additionally, in scientist-in-action videos, these concepts' application is demonstrated through real experiments in modern laboratories.

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Mitosis and Cytokinesis Stages

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