Cytokinesis Definition

Cytokinesis is a physical cell division mechanism that often follows mitosis. At the conclusion of the cell cycle in both mitosis and meiosis, eukaryotic cells physically divide their cytoplasm, membrane, and organelles to form two separate cells.

• In the majority of cells, cytokinesis begins at the anaphase stage and concludes in telophase, a period during which the chromosomes are fully segregated.
• Animal cells endure cytokinesis if a contractile ring of the cell’s microtubules generates a cleavage furrow, that divides the cell membrane in two.
• The microtubules produced during the earliest phases of cell division are those that are utilised during cytokinesis, and they help to restructure the newly formed cell.
• A cell plate that separates the plant cell into two forms inside the cell.
• Furthermore, cytokinesis only occurs once the chromosomes have fully separated. In addition to receiving a complete set of chromosomes and all the components of the cytoplasm and cell organelles, this guarantees that each daughter cell will

What happens during cytokinesis?

• Cytokinesis is the division of a parent cell into two daughter cells, each having a set of split chromosomes and half the cytoplasm and cell organelles of the parent cell. Comparable cytokinesis occurs in both plant and mammalian cells.
• Cell division often involves the creation of a cleavage furrow that divides the cells fairly evenly.
• Asymmetrical cell division, in which one cell absorbs the majority of the cytoplasm, can occur.
• A common example of asymmetrical cytokinesis is biogenesis, which results in a giant cell with three polar bodies. Spermatogenesis, a process of meiosis cell division, is symmetrical cytokinesis because the freshly formed sperm cells are identical in size and composition.
• In animal cells, the location of the mitotic spindles determines the cleavage furrow. In contrast, the cleavage furrow in plant cells is independent of the mitotic spindles.

Generally, cytokinesis takes place in four stages:

Initiation and formation of the cleavage furrow

• The first physical alteration during cytokinesis is the emergence of the cleavage furrow on the cell surface.
• As the furrow widens and spreads across the cell, the cell eventually splits in half.

Contraction and constriction

• This also goes by the name of abscission.
• Animal cells are accountable for cytokinesis due to the contractile ring, which is composed of actin, myosin, and regulatory proteins. This ring is generated under the surface of an animal cell during cell division.
• These rings possess the power to tighten up and squeeze the cell, splitting it in half.

Membrane Insertion

• Through the fusing of the intracellular vesicles, a new membrane is simultaneously created and introduced into the cell membrane close to the contractile ring.
• The cell can grow while the cytoplasmic division occurs thanks to the new membrane.

Upon completion of cytokinesis, two completely grown daughter cells are produced.

Cytokinesis in animal cells

• The contractile ring is thought to be involved in the animal cell’s cytokinesis process. The microtubules of the mitotic spindles are responsible for holding the contractile ring together.
• The division plane, also known as the contractile ring location, is controlled by these microtubules and cell signals, which also regulate the position of the contractile ring.
• The division plane generates the cleavage furrow, which finally pinches off and divides the cell into two cells.
• The contractile ring, which is composed of actin, myosin, and regulatory proteins, subsequently undergoes a contraction as well as a constriction phase.
• Actin and myosin are organised into a cortical network of the filaments filled with actin and myosin during the interphase. Actin filaments are rearranged as cell division proceeds, and myosin filaments build up to form contractile rings during anaphase.
• Actin-myosin and regulatory proteins place the contractile ring and function as the motor proteins that cause the muscle cells to contract.
• Myosin proteins bring the actin filament-rich muscle cells together to create an actin-myosin ring, which is crucial for excluding the cytoplasm and the cell organelles.
• The ring and the microtubules are left behind after the cytoplasm and organelles are excluded, generating the mid-body structure, which eventually splits.
• The plasma membrane is fused, and its cellular proteins are cut, separating the cells as the extracellular components holding the cell together disintegrate.
• The mid-body structures capture fragments of the endoplasmic reticulum that generate the gap junctions. This allows the divided cells to remain connected by the cytoplasm and remain related.

Cytokinesis in plant cells

• Plant cells vary significantly from animal cells in that they have an extra-rigid cell wall. As a result, plant cells require a particular type of microtubule to complete the process of cytokinesis. Phragmoplasts are the term for this.
• During telophase on the metaphase plate, Golgi vesicles produce vesicular spindle microtubules that transport vesicles and cellular components like cellulose to the new cell wall.
• The cell plate, where plant cytokinesis takes place, is created when these Golgi vesicles fuse in the middle, adjacent to the cell wall
• The cell plate continues to grow and emerge at the edge of the cell wall as the vesicles fuse more and more.
• The freshly formed cell plate receives vesicles of the cell wall from the phragmoplasts.
• As the Golgi membranes are incorporated into the plasma membrane, the enzymes, structural proteins, and glucose molecules deposited between the membranes by the Golgi apparatus during interphase contribute to the formation of the fresh cell wall.
• The complex and stiff matrix of the plant cell wall is formed by the interaction and combination of the cellulose transported by the phragmoplast.
• The plasma membrane separates the two freshly produced daughter cells after the cell has been divided by the cell plate.
• Plasmodium-trapped endoplasmic reticulum creates the plasmodesmata, a space or gap between the two cells that permits the movement of chemicals between them and the signalling of cells for cell-to-cell contact.

Applications of Cytokinesis

• The development of the block-cytokinesis micronuclei cytosome technique to analyse human cells was made possible by cytokinesis investigations.
• Tumorigenesis can result from cytokinesis that has failed, which has advanced cancer research in its understanding of oncogenesis and therapeutic targets of incomplete cytokinesis processes.

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