Anaphase

Anaphase is a crucial stage in cell division, occurring in both mitosis and meiosis. During this phase, separated chromatids or homologous chromosome pairs move toward opposite poles of the spindle apparatus. Anaphase follows metaphase, where chromosomes align along the cell's midline, and precedes telophase, the final step before cell division. In mitosis, individual chromatids are pulled apart to ensure each daughter cell receives a complete set of chromosomes, while in meiosis, homologous chromosome pairs segregate. 

1.0Activity during Anaphase

Anaphase initiates with the activation of the anaphase promoting complex, which marks the inhibitory chaperone, securin, for degradation through ubiquitination. Securin acts as a suppressor of the protease separase. The degradation of securin unleashes separase, leading to the cleavage of cohesin, a protein crucial for maintaining the cohesion between sister chromatids. 

This decisive event allows the separation of chromatids, a key step in accurate chromosome distribution during cell division. The process involves the orchestrated action of three distinct subclasses of microtubules exclusive to mitosis: kinetochore microtubules, interpolar microtubules, and astral microtubules. Kinetochore microtubules play a pivotal role in pulling the sister chromatids towards opposite poles by engaging with the centromeres, resulting in a distinctive V or Y-shaped configuration. 

Concurrently, interpolar microtubules and astral microtubules contribute forces that elongate the cell into an oval shape. This coordinated action of microtubules ensures the precise and orderly segregation of genetic material, a fundamental process for the formation of genetically identical daughter cells.

2.0Phases of Anaphase

Anaphase involves two key movements. First, anaphase A moves chromosomes to opposite poles of the dividing cell. Second, anaphase B separates the poles from each other, mainly driven by interpolar and astral microtubules.

Anaphase A   

In anaphase A, various forces come into play, but the central force predominates in driving the movement of chromatids. Microtubules, dynamic structures of the cytoskeleton, attach to the central region of chromosomes, known as the centromere, through protein complexes called kinetochores. 

As these attached microtubules undergo depolymerization and shorten, the collaborative action with motor proteins generates a force that pulls the chromosomes towards the centrosomes positioned at each pole of the cell. This concerted effort ensures the orderly and central movement of chromatids during this crucial phase of cell division.

Anaphase B

The second phase of anaphase operates through distinct mechanisms, with force generated by multiple actions. Interpolar microtubules initiate at each centrosome and converge at the equator of the dividing cell. As they push against each other, this mutual pressure causes the centrosomes to move apart. 

Simultaneously, astral microtubules originate at each centrosome and extend to the cell membrane, facilitating the pulling of each centrosome closer to the cell membrane. The motion induced by these microtubules results from a combination of microtubule growth or shrinkage, complemented by the involvement of motor proteins such as dyneins or kinesins.