During which phase of meiosis II do chromosomes condense?

During Prophase II of meiosis II, chromosomes condense, becoming more tightly packed and visible under a microscope. This phase follows the completion of meiosis I, which results in two haploid cells containing duplicated chromosomes. During Prophase II, the nuclear envelope, if it had reformed during Telophase I, begins to break down again, and the spindle apparatus starts to form. The condensation of chromosomes is a crucial step that prepares them for alignment and separation in the subsequent stages of meiosis II, specifically Metaphase II, where they will line up at the metaphase plate.

In contrast, during Metaphase II, the chromosomes are already condensed and lined up for separation. Anaphase II involves the separation of sister chromatids, while Telophase II is characterized by the decondensation of chromosomes and the reformation of the nuclear envelope as the cells complete division. Thus, the correct identification of Prophase II as the stage where condensation occurs aligns perfectly with the known processes of meiosis.