MPhases

MPhases, in the context of the eukaryotic cell cycle, refer to the stages during which duplicated chromosomes are segregated and the cell divides. The M phase includes mitosis, the nuclear division, and cytokinesis, the cytoplasmic division, and it follows interphase where the cell grows and DNA is replicated. M phase is typically shorter than interphase and is tightly regulated to ensure proper chromosome distribution.

Mitosis is commonly divided into prophase, prometaphase, metaphase, anaphase, and telophase. In prophase, chromatin condenses into visible chromosomes and the mitotic spindle begins to form. During prometaphase, the nuclear envelope breaks down and spindle microtubules attach to kinetochores. In metaphase, chromosomes align along the metaphase plate at the cell’s center. Anaphase drives the separation of sister chromatids toward opposite poles, and telophase concludes with the reformation of the nuclear envelope and the de-condensation of chromosomes.

Cytokinesis completes cell division by dividing the cytoplasm. In animal cells, a contractile actomyosin ring creates a contractile ring that forms a cleavage furrow, splitting the cell into two daughter cells. In plant cells, vesicles derived from the Golgi coalesce at the center to build a cell plate, which develops into separate cell membranes and a separating cell wall. The two daughter cells then enter the G1 phase of the next interphase.

Regulation of M phases involves cyclin-dependent kinases, especially Cdk1 bound to cyclin B, which orchestrate entry and progression through mitosis. The spindle assembly checkpoint ensures chromosomes are properly attached to the spindle before anaphase onset, helping preserve genomic integrity.