Which phase is the second stage of mitosis, during which the duplicated chromosomes' centromeres line up at the cell's equator?

• A. Metaphase
• B. Anaphase
• C. Prophase
• D. Telophase

Answer: (A)

The key idea here is how chromosomes are organized during mitosis. In this phase, the duplicated chromosomes’ centromeres line up along the cell’s equator, forming the metaphase plate. This alignment happens because spindle fibers from opposite poles attach to the kinetochores of each sister chromatid and pull them into a single plane, ensuring that sister chromatids will be separated accurately in the next stage. This precise arrangement is what distinguishes metaphase from the other stages: prophase involves chromosomes condensing and the nucleus breaking down, anaphase is when the chromatids are pulled apart toward the poles, and telophase is when new nuclei form around the separated chromosomes.