What stage of cell division is characterized by the separation of sister chromatids?

The stage of cell division characterized by the separation of sister chromatids is Anaphase. During this phase, the sister chromatids, which are identical copies of a chromosome, are pulled apart by spindle fibers attached to the centromere region. This action moves the separated chromatids toward opposite poles of the cell, ensuring that each new daughter cell will receive an identical set of chromosomes after division.

In contrast, during Prophase, the chromatin condenses to form visible chromosomes, and the mitotic spindle begins to form, but the sister chromatids have not yet separated. Metaphase involves the alignment of chromosomes at the cell's equatorial plane, but again, no separation occurs at this stage. Telophase follows Anaphase and includes the re-establishment of the nuclear envelope around the separated chromatids, and the chromosomes begin to de-condense, but the key action of separation has already occurred in Anaphase. Thus, Anaphase is distinctly defined by this separation process.