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

Comprised of five unique stages, mitosis is a form of division where a cells genetic material is partitioned between two daughter cells.&nbsp; First, during prophase in humans, nucleic chromatin condenses into x-shaped chromosomes composed of sister chromatid pairs attached at centromere junctions.
Concurrently, outside the nucleus, two l-shaped organelles called centrosomes migrate to opposite cell sides. As they do so, microtubule rods begin to grow from each, either towards the cell&#39;s interior or exterior forming a web-like spindle apparatus.
Next, the nuclear envelope dissolves during prometaphase, exposing the chromosomes to the cells other contents. Protein structures also appear on both sides of the centromeres, one for every chromatin.
Once these kinetochores form, extending interior microtubules fasten to them, with each sister chromatid being tethered to a different cell pole.
Mitosis then progresses to metaphase where the spindle apparatus rearranges the chromosomes so that they are similarly oriented in a fixed row along the cell&#39;s equator.
With anaphase, kinetochore afixed microtubules shorten and sister chromatids, now individually referred to as chromosomes, are dragged apart. These and other microtubule dynamics also elongate the cell.
Finally, the chromosomes land at opposite cell sides during telophase, where upon the spindle apparatus disbands. The genetic material loosens, and two nuclear envelopes, one around each chromosome set, arise.
During telophase, in a distinct process called cytokinesis, the cell is cytoplasmically divided. Thus, the end result of mitosis is a cell pair genetically identical to their precursor.

mitosis and cytokinesis

In eukaryotes, the cell division cycle is divided into distinct, coordinated cellular processes that include cell growth, DNA replication/chromosome duplication, chromosome distribution to daughter cells, and finally, cell division. The cell cycle is tightly regulated by its regulatory systems as well as extracellular signals that affect cell proliferation.
The processes of the cell cycle occur over approximately 24 hours (in typical human cells) and in two major distinguishable stages. The first stage is DNA replication, during the S phase of interphase. The second stage is the mitotic (M) phase, which involves the separation of the duplicated chromosomes into two new nuclei (mitosis) and cytoplasmic division (cytokinesis). The two phases are separated by intervals (G1 and G2 gaps), during which the cell prepares for replication and division.
<h4>The Process of Mitosis</h4>
Mitosis can be divided into five distinct stages&mdash;prophase, prometaphase, metaphase, anaphase, and telophase. Cytokinesis, which begins during anaphase or telophase (depending on the cell), is part of the M phase, but not part of mitosis.
<h4>Prophase</h4>
As the cell enters mitosis, its replicated chromosomes begin to condense and become visible as threadlike structures with the aid of proteins known as condensins. The mitotic spindle apparatus begins to form between the centrosomes&mdash;which were duplicated during S phase&mdash;and migrate to opposite poles of the cell. The spindle is made up of filamentous structures called microtubules that are comprised of tubulin protein monomers. Spindle microtubules start extending towards the condensed chromosomes. The nucleolus, a component of the nucleus that produces ribosomes, vanishes, indicating the impending breakdown of the nucleus.
<h4>Prometaphase</h4>
During prometaphase, the microtubule filaments from the spindle apparatus continue to grow, and the chromosomes finish condensing. The nuclear envelope completely breaks down, releasing the chromosomes. Some of the microtubules attach to the released chromosomes, binding at a protein structure called the kinetochore that is present on the centromere of each pair of sister chromatids. Spindle microtubules from opposite poles attach at the kinetochores and capture the condensed sister chromatid pairs. Spindle microtubules that do not attach to chromosomes&mdash;polar and astral microtubules&mdash;help push the spindles apart and anchor the spindle poles to the cell membrane.
<h4>Metaphase</h4>
The spindle microtubules align each pair of the fully condensed sister chromatids along the equator of the cell&mdash;at the metaphase plate. The cell is now ready to divide.
<h4>Anaphase</h4>
The microtubules from opposite spindle poles, which are attached to the kinetochore structure, shorten and separate the sister chromatids at the centromere. The cohesion proteins that hold the chromatids together now break down. The shortening kinetochore microtubules cause each chromatid of the pair&mdash;now called chromosomes&mdash;to migrate to an opposite pole.
<h4>Telophase</h4>
Once the chromosomes reach opposite poles of the cell, they decondense and uncoil to form chromatin. The spindle microtubule filaments depolymerize into their tubulin monomers, which are then utilized as cytoskeletal elements in daughter cells. Nuclear envelopes reassemble around each set of chromosomes.
<h4>Cytokinesis</h4>
During cytokinesis in animal cells, actin filaments form a contractile ring in the plasma membrane to create a cleavage furrow, which eventually pinches the cell into two. In plant cells, vesicles from the Golgi apparatus carrying glucose, enzymes and structural proteins join to form a new cell plate at the location of the former metaphase plate. The growing cell plate fuses with the plasma membranes on each side, eventually forming a new cell wall that divides the cell into two.
Mitosis is now complete, generating two daughter cells that are identical to the parent cell. In most human cells, mitosis accounts for about one hour of the approximately 24-hour cell cycle.

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

Education

JoVE Core

Molecular Biology

Unit 2

Cell Division

KEY TERMS AND CONCEPTS

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 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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