Which phase involves chromosomes aligning at the cell's equator?

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

Answer: (A)

Chromosome alignment at the cell's equator occurs during metaphase. The spindle apparatus, made of microtubules radiating from opposite poles, attaches to kinetochores at the centromeres of each chromosome. These fibers pull on the kinetochores until the chromosomes are lined up in a single plane along the middle of the cell, the metaphase plate. This precise arrangement ensures that, in the next phase, sister chromatids can be pulled apart accurately to opposite ends of the cell. Before this stage, chromosomes condense and the spindle forms (prophase); after, the centromeres split and chromatids are pulled toward the poles (anaphase), followed by the chromosomes arriving at the poles and the nucleus re-forming (telophase).