1. Formation of the Contractile Ring:
- During late anaphase, as the chromosomes are pulled apart, a band of microfilaments composed primarily of actin and myosin assembles beneath the plasma membrane at the future site of division. This band is called the contractile ring.
2. Contraction of the Contractile Ring:
- The actin and myosin filaments within the contractile ring slide past each other, much like the sliding filament mechanism in muscle contraction. This contraction pulls the plasma membrane inward, creating a deep furrow.
3. Formation of the Cleavage Furrow:
- The inward movement of the plasma membrane results in the formation of a progressively deeper furrow, known as the cleavage furrow. This furrow continues to constrict the cell, ultimately dividing the cytoplasm into two daughter cells.
4. Completion of Cytokinesis:
- As the cleavage furrow pinches off, a small bridge of cytoplasm remains connecting the two daughter cells. This bridge eventually breaks, completely separating the daughter cells.
Key Players in Cleavage Furrow Formation:
- Actin: Provides the structural framework for the contractile ring.
- Myosin: A motor protein that generates the force for contraction.
- Microtubules: Help position the contractile ring at the equator of the cell.
- Plasma membrane: Provides the boundary for the dividing cell.
Note: The position of the cleavage furrow is determined by the location of the spindle poles, ensuring that the chromosomes are evenly distributed to each daughter cell.
This process of cleavage furrow formation is essential for the proper division of the cytoplasm and the creation of two genetically identical daughter cells.
