During which phase do sister chromatids separate?

Sister chromatids separate during anaphase, which is a critical phase of cell division (whether in mitosis or meiosis). During this stage, the proteins that hold the sister chromatids together are cleaved, allowing them to move towards opposite poles of the cell. This separation is essential for ensuring that each new daughter cell receives an identical set of chromosomes.

The process begins with the alignment of chromosomes at the cell's equatorial plane during metaphase, but it is in anaphase that the actual splitting and movement occurs. This movement is facilitated by the spindle fibers, which contract and pull the chromatids apart. As a result, the number of chromosomes effectively doubles, ensuring that the genetic material is accurately distributed between the dividing cells.

In contrast, prophase is characterized by the condensation of chromatin into visible chromosomes and the formation of the mitotic spindle, while telophase marks the reformation of the nuclear envelope around separated chromosomes. Therefore, the phase where sister chromatids separate so that each daughter cell will receive the correct number of chromosomes is distinctly anaphase.