During which phase(s) of mitosis are duplicated chromosomes visible?

Duplicated chromosomes are visible during all phases of mitosis. However, they are most clearly visible and distinguishable during the metaphase. Here are the steps of mitosis where duplicated chromosomes are visible:

1. Prophase: This is the first stage of mitosis. The duplicated chromosomes start to condense and become visible under a microscope. The nucleolus disappears and the mitotic spindle begins to form.

2. Prometaphase: The nuclear envelope breaks down, allowing the spindle fibers to interact with the chromosomes. The chromosomes become more condensed and clearly visible.

3. Metaphase: The chromosomes align at the metaphase plate (the equatorial plane of the cell). This is the phase where the chromosomes are most clearly visible and distinguishable.

4. Anaphase: The sister chromatids separate and move towards opposite poles of the cell. The chromosomes are still visible, but start to become less distinguishable as they move apart.

5. Telophase: The separated chromosomes reach the opposite poles of the cell. They start to decondense and become less visible as the nuclear envelope re-forms.

So, in summary, duplicated chromosomes are visible during all phases of mitosis, but they are most clearly visible during the metaphase.