citokinesis

Cytokinesis is the physical division of the cytoplasm that completes cell division after mitosis or meiosis, producing two distinct daughter cells. In animal cells, a contractile actomyosin ring forms at the cell cortex and constricts the membrane to create a cleavage furrow that pinches the cell membrane inward, splitting the cytoplasm. In plant cells, vesicles derived from the Golgi apparatus coalesce at the center of the cell to form a cell plate, which enlarges and fuses with the parental membrane to separate the two daughter cells and establish a separating cell wall.

Regulation of cytokinesis involves coordination with chromosome segregation. Rho-family GTPases, especially RhoA, organize the actin cytoskeleton to drive furrow formation, while mitotic kinases and cyclin-dependent kinases help time cytokinesis with mitotic exit. In animal cells, structural proteins such as myosin II, anillin, and septins stabilize the contractile ring. In plant cells, microtubule-guided vesicle traffic and the phragmoplast direct cell plate assembly.

Timing and coordination: Cytokinesis typically begins in late anaphase and completes during telophase, marking the end of cell division alongside the completion of nuclear division. In meiosis, cytokinesis occurs after the two successive chromosome segregations, yielding haploid gametes.

Abnormalities: Failures of cytokinesis can lead to multinucleate or polyploid cells and are associated with developmental issues and various diseases, including cancer. Cytokinesis is a distinct and essential step that ensures proper distribution of the cytoplasm and organelles between daughter cells.