Metaphase is characterized by which of the following events?

• A. Chromosomes aligning at the cell's equatorial plane
• B. Sister chromatids separating and moving toward opposite poles
• C. The nuclear envelope re-forming around chromosomes
• D. Chromatin condensing into visible chromosomes

Answer: (A)

Verified step by step guidance

1. Understand the stages of mitosis and their key characteristics: prophase, metaphase, anaphase, and telophase.
2. Recall that metaphase is the stage where chromosomes become highly condensed and align at the cell's equatorial plane (also called the metaphase plate).
3. Recognize that sister chromatids separate and move toward opposite poles during anaphase, which follows metaphase.
4. Note that the nuclear envelope re-forms around chromosomes during telophase, the final stage of mitosis.
5. Conclude that the defining event of metaphase is the alignment of chromosomes at the cell's equatorial plane.