1. Contractile Ring Formation: During late anaphase or early telophase of mitosis, a ring of microfilaments composed of the protein actin forms just beneath the plasma membrane. This ring is associated with the protein myosin, which acts as a motor protein.
2. Ring Contraction: The actin-myosin ring contracts, pulling the plasma membrane inwards. This inward pulling creates a shallow groove called the cleavage furrow.
3. Furrow Deepening: The contractile ring continues to constrict, deepening the cleavage furrow. This process is fueled by the hydrolysis of ATP, which provides energy for myosin's motor activity.
4. Cell Division: As the furrow continues to deepen, it eventually pinches off the cell entirely, separating the two daughter cells. This process requires the coordinated action of actin, myosin, and various regulatory proteins.
Key points to remember:
* Cytokinesis in animal cells is driven by the assembly and contraction of a contractile ring made of actin and myosin filaments.
* The furrow formation process begins at the cell's equator and proceeds inward.
* The process is dependent on the presence of the mitotic spindle, which provides the necessary structural support for the contractile ring.
* Cytokinesis typically occurs simultaneously with the completion of nuclear division (telophase).
Comparison with Plant Cells:
It's important to note that cytokinesis in plant cells differs significantly from the process in animal cells. Plant cells utilize a cell plate formation, where new cell wall material is deposited between the daughter nuclei, ultimately separating the two cells.
