Cytoskeleton and motility · USMLE Step 1

Which cytoskeletal filaments are most directly involved in cytokinesis (cell division) during cleavage of a dividing cell in animal cells?

  1. Microtubules forming the mitotic spindle
  2. Intermediate filaments forming nuclear lamina
  3. Actin microfilaments forming the contractile ring
  4. Collagen fibers facilitating separation
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Correct answer: Actin microfilaments forming the contractile ring

During cytokinesis, actin microfilaments (with myosin) assemble a contractile ring at the cleavage furrow, which constricts to divide the cell into two daughter cells.

Difficulty: Medium Question 13 of 21

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