Citokinezis

Cytokinesis is the process that completes cell division by partitioning the cytoplasm and cytoplasmic organelles into two daughter cells after the completion of mitosis or meiosis. It follows karyokinesis, the division of the nucleus, and ensures two viable cells with roughly equal cytoplasmic content.

Mechanisms vary among organisms. In animal cells, a contractile ring of actin filaments forms a contractile ring at the cell equator, causing a contractile cleavage furrow that constricts the plasma membrane and divides the cytoplasm. The final severing is called abscission, which occurs at the midbody. In plant cells, rigid cell walls prevent furrow formation; instead, vesicles derived from the Golgi apparatus coalesce at the center to form a cell plate, which develops into separating cell walls, dividing the cytoplasm.

Some organisms show variations: fungal cells also use an actomyosin ring and often form a septum; in many protists, cytokinesis may involve furrowing or cell plate-like mechanisms depending on lineage. Regulation involves coordination with mitotic spindle dynamics and cytoskeletal rearrangements, and is driven by signaling pathways including Rho family GTPases and cyclin-dependent kinases. Proper cytokinesis is essential for maintaining genome integrity and normal cell size; defects can lead to multinucleation, aneuploidy, or failed cell separation.