Final answer:
At the end of interphase and during metaphase of mitosis and meiosis II, chromosomes are in the form of unseparated sister chromatids. It is during anaphase that they separate, and by telophase, they are individual chromosomes in divided cells.
Step-by-step explanation:
Chromosomes are in their unseparated, sister-chromatid form at the end of interphase and also during metaphase of both mitosis and meiosis II. It is during anaphase that sister chromatids separate and move to opposite poles of the cell. Specifically, at the end of interphase, chromosomes have been replicated but are yet to be condensed and are not visible under a microscope. Chromosomes are in unseparated, sister-chromatid form at the end of prophase. During prophase of mitosis, the chromatin condenses into visible chromosomes, with each chromosome having its identical partner attached, forming sister chromatids. This is the first phase of mitosis, where the nucleolus disappears and the nuclear envelope disintegrates.
As cells enter prophase, chromosomes begin to condense and become visible. During metaphase, these sister chromatids are aligned at the cell's equator, attached at their centromeres, before being pulled apart in anaphase. Finally, in telophase, sister chromatids have already been separated, and the cell is completing its division to form two distinct cells.