Mitosis mechanics During which sub-phase do kinetochore microtubules pull chromosomes toward opposite spindle poles?

Introduction / Context:
Mitosis includes precise, named movements of chromosomes. Understanding the difference between anaphase A and anaphase B helps students interpret microscopy images and drug effects that target spindle dynamics.

Given Data / Assumptions:

• Anaphase is subdivided into A and B.
• Kinetochore microtubules attach chromosomes to spindle poles via kinetochores.
• Interpolar microtubules contribute to spindle elongation.

Concept / Approach:
In anaphase A, chromosome movement results from shortening of kinetochore microtubules and poleward forces at kinetochores. In anaphase B, the spindle elongates due to sliding of antiparallel interpolar microtubules and pole separation.

Step-by-Step Solution:

Verification / Alternative check:
Standard cell biology diagrams show anaphase A (chromosomes move to poles) preceding or overlapping with anaphase B (spindle elongation).

Why Other Options Are Wrong:

• Anaphase B emphasizes spindle elongation, not primary chromosome pulling.
• Metaphase is alignment at the metaphase plate.
• Telophase involves reformation of nuclei, not poleward pulling.
• Prophase includes chromosome condensation and spindle assembly.

Common Pitfalls:
Equating all chromosome movements with “anaphase” without distinguishing A vs. B mechanics.

Final Answer:
Anaphase A