Tsytokineesin

Tsytokineesin is the process by which a parent cell divides its cytoplasm to produce two daughter cells following the segregation of its chromosomes. In most eukaryotic cells, it is the final stage of cell division and occurs after karyokinesis, the division of the nucleus. Cytokinesis ensures that cellular components are distributed between the two new cells and completes the formation of distinct daughter cells in both mitosis and meiosis.

In animal cells, cytokinesis typically begins with the assembly of a contractile actomyosin ring beneath the cell cortex, forming a contractile network that constricts the cell membrane to create a cleavage furrow. The furrow ingresses until the cytoplasm is divided. Vesicle trafficking and membrane remodeling contribute to abscission, the final severing of the remaining cytoplasmic bridge, often involving ESCRT-III complexes. The central spindle and associated microtubules provide spatial cues that guide the positioning of the cleavage furrow.

In plant cells, cytokinesis proceeds differently due to rigid cell walls. Vesicles derived from the Golgi apparatus coalesce at the center of the cell to form a cell plate, guided by a phragmoplast microtubule apparatus. The cell plate expands outward and coalesces with the parental cell wall to establish two separate cells, each with its own plasma membrane and cell wall.

Cytokinesis is tightly coordinated with the cell cycle and cytoskeletal dynamics. Errors in cytokinesis can lead to polyploidy or aneuploidy, contributing to genomic instability and various disease processes, including cancer. While the core concept is conserved, mechanistic details vary across organisms.