What is the main action that occurs during anaphase?

Anaphase is a critical stage during cell division, particularly in mitosis and meiosis, where the primary action involves the separation of sister chromatids. During this phase, the cohesion that holds the sister chromatids together is cleaved, allowing them to move toward opposite poles of the cell. This movement is facilitated by the spindle fibers that pull the chromatids apart, ensuring that each new daughter cell receives an identical set of chromosomes. This separation ensures that genetic material is accurately divided, maintaining the same genetic information in each resulting cell.

Understanding the process of anaphase is crucial for comprehending how cells reproduce and how genetic material is distributed during cell division. Other actions described in the choices relate to different stages of cell division. For instance, pairing of chromosomes occurs during prophase, while alignment in the middle happens during metaphase. The phrase referring to cells beginning to divide points to the later stages of cytokinesis, which follows anaphase. Thus, the defining action of sister chromatids separating is what characterizes anaphase specifically.