During anaphase, what process occurs involving sister chromatids?

During anaphase, the key event that occurs is the separation and movement of sister chromatids toward opposite poles of the cell. This is a critical stage in cell division, specifically in both mitosis and meiosis.

At the onset of anaphase, the cohesin proteins that hold the sister chromatids together are cleaved, allowing them to be pulled apart by the spindle fibers attached to the kinetochores. Each sister chromatid, now an independent chromosome, is then directed toward opposite ends of the cell. This separation is essential for ensuring that each daughter cell receives an identical set of chromosomes, maintaining genetic consistency.

The other options describe processes that either do not occur during anaphase or are unrelated to the specific actions involved with sister chromatids. Replication of chromatids occurs during the S phase of interphase, crossing-over takes place during prophase I of meiosis, and combining together would imply a loss of distinct chromosomes, which contradicts the purpose of anaphase. Thus, the process of sister chromatids being pulled apart is fundamental to the correct distribution of genetic material during cell division.