Introduction

Cytokinesis is the process by which the cytoplasm of a parent cell divides into two daughter cells. It marks the final stage of cell division, following mitosis (in somatic cells) or meiosis (in gametes). This process ensures that each daughter cell receives a sufficient amount of cytoplasm, organelles, and genetic material necessary for survival and function. Cytokinesis differs between animal and plant cells due to structural differences, particularly the presence of a rigid cell wall in plant cells.

Phases of Cytokinesis

Cytokinesis generally occurs in conjunction with the final phase of mitosis or meiosis, known as telophase. The process can be divided into the following key steps:

1. Initiation

• Cytokinesis begins during anaphase or telophase.
• Signals from the mitotic spindle guide the positioning of the division plane.
• In animal cells, a contractile ring composed of actin and myosin filaments starts forming beneath the plasma membrane at the equatorial region.
• In plant cells, vesicles from the Golgi apparatus accumulate at the center of the cell, forming the early cell plate.

2. Constriction or Cell Plate Formation

• Animal Cells: The contractile ring tightens, creating a cleavage furrow that deepens progressively.
• Plant Cells: The vesicles fuse to form a cell plate, which gradually extends outward, separating the cytoplasm.

3. Completion of Cytokinesis

• In animal cells, the furrow deepens until the cytoplasm is completely divided, resulting in two separate daughter cells.
• In plant cells, the cell plate fully develops into a new cell wall, partitioning the cytoplasm into two distinct compartments.

Differences in Cytokinesis: Animal vs. Plant Cells

Feature	Animal Cells	Plant Cells
Mechanism	Formation of a cleavage furrow	Formation of a cell plate
Main Structures Involved	Contractile ring of actin and myosin	Vesicles from the Golgi apparatus
Division Method	Membrane pinching inward	Cell plate expansion from center
Presence of Cell Wall	No cell wall	Rigid cell wall present

Significance of Cytokinesis

• Ensures equal distribution of cytoplasm and organelles.
• Helps maintain proper cell size and function.
• Completes the process of cell division, allowing for growth, repair, and reproduction.
• In multicellular organisms, contributes to tissue formation and development.

Conclusion

Cytokinesis is a crucial step in cell division, ensuring that each daughter cell receives the necessary cellular components. While the basic process remains the same across different organisms, variations exist between animal and plant cells due to structural differences. Without cytokinesis, cells would contain multiple nuclei, leading to abnormal development and functioning.