Cytokinesis is the division of the cytoplasm, which occurs after nuclear division (mitosis or meiosis) and results in two daughter cells. Here's how it happens in animal cells:
1. Cleavage Furrow Formation:
* Actin and Myosin: This process begins with the assembly of a contractile ring made up of microfilaments, specifically actin and myosin. These proteins are found in the cytoplasm beneath the plasma membrane.
* Contraction: The actin filaments slide past each other, driven by the motor protein myosin. This contraction pulls the plasma membrane inwards, creating a shallow groove called the cleavage furrow.
2. Furrow Deepening and Invagination:
* Plasma Membrane Movement: As the contractile ring continues to contract, the cleavage furrow deepens and moves inward. The plasma membrane is pulled inwards, effectively pinching the cell in two.
* Microtubule Involvement: Microtubules emanating from the spindle poles may also play a role in guiding the cleavage furrow to the correct location, ensuring the cytoplasm is divided equally.
3. Cell Separation:
* Final Pinch: The cleavage furrow eventually pinches off completely, separating the two daughter cells. This process is facilitated by the breakdown of the contractile ring components.
* Daughter Cells: Each daughter cell receives a full set of chromosomes and organelles, ensuring that each cell is a complete and functional unit.
Key Points:
* Actin and Myosin: These proteins are crucial for the formation and contraction of the cleavage furrow.
* Cleavage Furrow: This groove is a defining feature of cytokinesis in animal cells.
* Microtubule Role: Microtubules may help guide the furrow and ensure proper division.
* Equal Distribution: Cytokinesis ensures that each daughter cell receives an equal share of cytoplasm and organelles.
Note: Plant cells have a different mechanism for cytokinesis, involving the formation of a cell plate instead of a cleavage furrow.
