When do sister chromatids separate during mitosis?

Sister chromatids separate during anaphase of mitosis. This is a critical phase in the cell cycle where the centromeres that hold the sister chromatids together split, allowing the individual chromatids to be pulled apart towards opposite poles of the cell.

During prophase, the chromosomes condense and become visible, and the nuclear envelope begins to break down, but the chromatids are still connected at the centromeres. In metaphase, the chromosomes align along the equatorial plane of the cell, known as the metaphase plate, but separation has not yet occurred. It is only in anaphase that the action of the spindle fibers pulls the sister chromatids apart, ensuring that each daughter cell will receive an identical set of chromosomes. Telophase, which follows anaphase, involves the reformation of the nuclear envelope around each set of separated chromatids and the beginning of cytoplasm division, but this is after the separation has already taken place. Thus, anaphase is the correct phase where sister chromatids are separated and moved to opposite ends of the cell.