In which phase of cell division do sister chromatids separate?

During cell division, sister chromatids separate during anaphase. This phase follows metaphase, where chromosomes align at the cell's equatorial plane. In anaphase, the proteins that hold the sister chromatids together are cleaved, allowing them to move towards opposite poles of the cell. This separation is crucial because it ensures that each daughter cell will receive an identical set of chromosomes. By the end of anaphase, the chromatids are fully separated and are now termed individual chromosomes.

In contrast, prophase is characterized by the condensation of chromatin into visible chromosomes and the breakdown of the nuclear envelope, but sister chromatids do not yet separate. Metaphase involves the alignment of chromosomes at the cell's equator, and telophase occurs after anaphase, where the separated chromosomes begin to de-condense and the nuclear envelope re-forms around each set. Thus, anaphase is the definitive phase where the actual separation of sister chromatids occurs.