During metaphase, which of the following best describes what happens to the chromosomes?

• A. Chromosomes line up in the middle of the cell
• B. The nucleus disappears
• C. Chromatids separate and move to opposite poles
• D. Cytoplasm divides

Answer: (A)

During metaphase, chromosomes line up along the middle of the cell, at the metaphase plate, with sister chromatids held together at their centromeres and attached to spindle fibers from opposite poles. This precise alignment, balanced by tension from the attached microtubules, sets up equal separation when the next stage begins. The nucleus has already broken down earlier, chromatids don’t separate until the next stage (anaphase), and cytokinesis—the division of the cytoplasm—happens after mitosis. So the defining event here is the chromosomes lining up in the middle.