Cell division is one of the most fundamental processes in biology. It allows organisms to grow, replace damaged cells, and reproduce. But dividing a cell involves more than simply copying and separating its DNA. Once the chromosomes have been distributed, the cell must also physically split into separate daughter cells. That final separation is called cytokinesis.
Cytokinesis is the process that divides the cytoplasm and cell membrane of a parent cell, producing two daughter cells after chromosome segregation. Although it is closely coordinated with mitosis or meiosis, cytokinesis is distinct from nuclear division. In animal cells, the membrane typically pinches inward; in plant cells, a new partition forms between the daughter cells.
Understanding cytokinesis helps explain how a single dividing cell becomes two independent cells and why accurate cell division depends on coordinating chromosome separation with the physical division of the cell.
What is cytokinesis?
Cytokinesis is the process that physically separates one dividing cell into two daughter cells. It usually occurs near the end of cell division, after the chromosomes have been separated during mitosis or meiosis.
While mitosis divides the cell’s duplicated chromosomes between two nuclei, cytokinesis divides the cell itself. The result is typically two separate cells, each enclosed by its own plasma membrane and containing its share of the cell’s cytoplasm and organelles.
Cytokinesis is therefore the final physical step that turns chromosome separation into two independent cells. It is closely coordinated with nuclear division, but the two processes are not the same.
How cytokinesis fits into cell division
Before a cell divides, it copies its DNA so that each future daughter cell can receive a complete set of genetic information. During mitosis, the duplicated chromosomes are separated into two groups, and each group becomes associated with a new nucleus.
Cytokinesis then partitions the rest of the cell around those two nuclei.
The timing is not identical in every cell. In many animal cells, cytokinesis begins while mitosis is still finishing, as the cell starts to constrict around its middle. In other cells, particularly some plant cells, the physical separation process follows a different sequence because of the rigid cell wall.
The important distinction is that mitosis separates chromosomes, whereas cytokinesis separates the cell.
How cytokinesis works in animal cells
In animal cells, cytokinesis occurs by creating a constriction called the cleavage furrow. The furrow begins as an indentation in the plasma membrane near the cell’s equator—the region between the two groups of chromosomes.
A ring of protein filaments forms just beneath the cell membrane at this location. The ring contains mainly actin and myosin, proteins that interact to produce contraction. As the ring tightens, it pulls the membrane inward, progressively narrowing the connection between the two halves of the cell.
Eventually, only a narrow bridge of membrane and cytoplasm connects the two daughter cells. This bridge is then resolved, completing their physical separation.
Cytokinesis must occur at the correct location. The cell’s division machinery uses signals associated with the mitotic spindle—the structure that organizes chromosome separation—to help position the cleavage furrow between the two chromosome groups. This coordination helps ensure that each daughter cell receives the appropriate chromosome complement.
How cytokinesis differs in plant cells
Plant cells cannot divide by simply pinching inward because their rigid cell walls resist the constriction used by animal cells.
Instead, a plant cell builds a new structure called a cell plate between the two daughter nuclei. Small membrane-bound compartments accumulate in the center of the dividing cell and fuse with one another. Their membranes expand outward until they connect with the existing cell membrane.
The developing cell plate becomes the foundation of a new cell wall separating the daughter cells. Plant cytokinesis therefore builds a partition from the inside outward rather than squeezing the original cell membrane inward.
This difference shows how the mechanics of cell division are adapted to a cell’s physical structure.
What happens to the cytoplasm during cytokinesis?
Cytokinesis divides more than the plasma membrane. The cytoplasm, which contains organelles, proteins, membranes, nutrients, and other cellular components, must also be distributed between the daughter cells.
The distribution is not necessarily perfectly equal. Cells can regulate how organelles and other components are partitioned according to their needs. Some dividing cells deliberately produce daughter cells of different sizes or with different amounts of particular cellular materials.
Even when the two daughter cells are broadly similar, successful cytokinesis requires coordinated remodeling of the cell’s internal structures. The goal is to produce two viable cells capable of functioning independently.
When does cytokinesis begin and end?
Cytokinesis generally begins during the later stages of mitosis and finishes after the chromosomes have been separated. In animal cells, the cleavage furrow becomes visible as the cell approaches the end of mitosis and deepens as the daughter nuclei form.
The final stage is sometimes called abscission. During abscission, the narrow bridge connecting the two nearly separated daughter cells is remodeled and ultimately cut, producing two distinct cells.
This final separation is carefully controlled. The cell must ensure that chromosome segregation and other late stages of division are sufficiently complete before the physical connection is severed.
Why cytokinesis matters
A cell can successfully separate its chromosomes and still fail to complete cell division. If cytokinesis does not occur properly, the resulting cell may contain multiple nuclei within a single cell or may acquire an abnormal number of chromosomes or cellular components.
Errors in cell division can have serious consequences because daughter cells inherit the products of the division process. In multicellular organisms, abnormal division can contribute to developmental problems or disease.
Cytokinesis is therefore not merely the last visible step of cell division. It is a carefully coordinated process that connects accurate chromosome segregation with the production of functional daughter cells.
Cytokinesis in mitosis and meiosis
Cytokinesis can occur after both mitosis and meiosis, but its role differs in the two processes.
In mitosis, one round of chromosome duplication is followed by one nuclear division. Cytokinesis generally produces two daughter cells.
In meiosis, the cell undergoes two successive nuclear divisions after a single round of DNA replication. Cytokinesis may occur after each division, ultimately contributing to the formation of four cells in the typical meiotic sequence.
The exact timing and extent of cytokinesis can vary among organisms and cell types. Some cells complete cytokinesis between meiotic divisions, while others delay or modify the process. What remains fundamental is its role in physically partitioning cellular material as nuclear division proceeds.
The key idea
Cytokinesis is the physical separation of a dividing cell into daughter cells. In animal cells, an actin-and-myosin contractile ring drives a cleavage furrow inward until the cell separates. In plant cells, vesicles build a cell plate that develops into a new partition between the daughter cells.
Mitosis makes sure the duplicated chromosomes are distributed into separate nuclei; cytokinesis completes the job by dividing the cell around them. Together, these coordinated processes transform one parent cell into new daughter cells with the genetic and cellular machinery needed to function.
