<P> The word cytokinesis (/ ˌsaɪtoʊkaɪˈniːsɪs, - tə -, - kə - /) uses combining forms of cyto - + kine - + - sis, New Latin from Classical Latin and Ancient Greek, reflecting "cell" and kinesis ("motion, movement"). </P> <P> Originally origin of this term is from Greek κύτος - kytos = a holow, Latin derivative cyto = cellular + κίνησις--kínesis = movement . </P> <P> Animal cell cytokinesis begins shortly after the onset of sister chromatid separation in the anaphase of mitosis . The process can be divided to the following distinct steps: anaphase spindle reorganization, division plane specification, actin - myosin ring assembly and contraction, and abscission . Faithful partitioning of the genome to emerging daughter cells is ensured through the tight temporal coordination of the above individual events by molecular signaling pathways . </P> <P> Animal cell cytokinesis starts with the stabilization of microtubules and reorganization of the mitotic spindle to form the central spindle . The central spindle (or spindle midzone) forms when non-kinetochore microtubule fibres are bundled between the spindle poles . A number of different species including H. sapiens, D. melanogaster and C. elegans require the central spindle in order to efficiently undergo cytokinesis, although the specific phenotype described when it is absent varies from one species to the next (for example, certain Drosophila cell types are incapable of forming a cleavage furrow without the central spindle, whereas in both C. elegans embryos and human tissue culture cells a cleavage furrow is observed to form and ingress, but then regress before cytokinesis is complete). The process of mitotic spindle reorganization and central spindle formation is caused by the decline of CDK1 activity during anaphase . The decline of CDK1 activity at the metaphase - anaphase transition leads to dephosphorylating of inhibitory sites on multiple central spindle components . First of all, the removal of a CDK1 phosphorylation from a subunit of the CPC (the chromosomal passenger complex) allows its translocalization to the central spindle from the centromeres, where it is located during metaphase . Besides being a structural component of the central spindle itself, CPC also plays a role in the phosphoregulation of other central spindle components, including PRC1 (microtubule bundling protein required for cytokinesis 1) and MKLP1 (a kinesin motor protein). Originally inhibited by CDK1 - mediated phosphorylation, PRC1 is now able to form a homodimer that selectively binds to the interface between antiparallel microtubules, facilitating spatial organization of the microtubules of the central spindle . MKLP1, together with the Rho - family GTPase activating protein CYK - 4 (also termed MgcRacGAP), forms the centralspindlin complex . Centralspindlin binds to the central spindle as higher - order clusters . The centralspindlin cluster formation is promoted by phosphorylation of MLKP1 by Aurora B, a component of CPC . In short, the self - assembly of central spindle is initiated through the phosphoregulation of multiple central spindle components by the decline of CDK1 activity, either directly or indirectly, at the metaphase--anaphase transition . The central spindle may have multiple functions in cytokinesis including the control of cleavage furrow positioning, the delivery of membrane vesicles to the cleavage furrow, and the formation of the midbody structure that is required for the final steps of division . </P>

Which organelle makes the primary component of the plasma membrane