Mitosis landmarks — alignment and separation events Which phase of mitosis is characterized by chromosomes aligned at the cell equator and, at the transition, centromeres divide to allow sister chromatids to move apart?

Introduction / Context:
Mitosis proceeds through ordered stages that first align and then separate sister chromatids. Discriminating metaphase from anaphase hinges on understanding when centromere cohesion is released.

Given Data / Assumptions:

• Metaphase: chromosomes are aligned at the metaphase plate; cohesion still holds sister chromatids together.
• Anaphase: separase cleaves cohesin; centromeres split and chromatids move to opposite poles.
• Interphase and prophase do not feature alignment/separation at the plate.

Concept / Approach:

Although alignment is the hallmark of metaphase, the question explicitly includes the event ‘‘centromeres divide,’’ which defines the metaphase–anaphase transition. Therefore, the correct phase associated with centromere division and poleward movement is anaphase.

Step-by-Step Solution:

Verification / Alternative check:

Live imaging and biochemical assays show cohesin cleavage and anaphase onset coincident with centromere separation, confirming anaphase as the correct stage.

Why Other Options Are Wrong:

Metaphase has alignment but no centromere division. Prophase features chromosome condensation; interphase is not part of mitosis; telophase follows chromatid arrival at poles.

Common Pitfalls:

Choosing metaphase based solely on alignment; the question’s inclusion of centromere division shifts the answer to anaphase.

Final Answer:

anaphase