During eukaryotic cell division, what structure directly moves chromosomes toward opposite poles of the cell?

• A. Actin microfilaments in the contractile ring that pinch the cell into two during cytokinesis
• B. Spindle microtubules (kinetochore microtubules) that attach to kinetochores and shorten to pull sister chromatids apart
• C. Centrioles that bind directly to chromosomes and drag them to opposite poles
• D. Intermediate filaments that form the nuclear lamina and pull chromosomes during anaphase

Answer: (B)

Verified step by step guidance

1. Understand the phases of eukaryotic cell division, focusing on mitosis where chromosomes are separated into daughter cells.
2. Identify the key structures involved in chromosome movement: spindle microtubules, actin microfilaments, centrioles, and intermediate filaments.
3. Recall that spindle microtubules, specifically kinetochore microtubules, attach to the kinetochores on chromosomes during metaphase.
4. Recognize that during anaphase, these kinetochore microtubules shorten, pulling sister chromatids toward opposite poles of the cell.
5. Conclude that the structure directly responsible for moving chromosomes toward opposite poles is the spindle microtubules (kinetochore microtubules), not actin microfilaments, centrioles, or intermediate filaments.