During eukaryotic cell division, what structure is primarily responsible for moving sister chromatids to opposite poles of the cell?

• A. Actin microfilaments of the contractile ring
• B. Kinetochore microtubules of the mitotic spindle
• C. Intermediate filaments that shorten to pull chromatids apart
• D. Centrioles that migrate and drag chromatids through the cytosol

Answer: (B)

Verified step by step guidance

1. Understand the context: During eukaryotic cell division, specifically mitosis, sister chromatids must be separated and moved to opposite poles of the cell to ensure each daughter cell receives an identical set of chromosomes.
2. Identify the key structures involved in chromosome movement: The mitotic spindle is a structure made of microtubules that orchestrates the separation of chromatids. It includes different types of microtubules such as kinetochore microtubules, polar microtubules, and astral microtubules.
3. Focus on the role of kinetochore microtubules: These microtubules attach directly to the kinetochores, which are protein complexes assembled on the centromere of each chromatid. The kinetochore microtubules exert forces that pull sister chromatids apart toward opposite spindle poles.
4. Contrast with other options: Actin microfilaments of the contractile ring are involved in cytokinesis (the physical division of the cytoplasm), not in moving chromatids. Intermediate filaments do not play a role in chromatid movement. Centrioles help organize the spindle but do not directly drag chromatids.
5. Conclude that the primary structure responsible for moving sister chromatids to opposite poles during mitosis is the kinetochore microtubules of the mitotic spindle.