Which cytoskeletal component primarily drives the formation of the cleavage furrow during cytokinesis in animal cells?

• A. Microtubules
• B. Actin filaments
• C. Intermediate filaments
• D. Ribosomes

Answer: (B)

Actin filaments drive the cleavage furrow by forming a contractile ring beneath the plasma membrane. This ring shortens as actin works with myosin motors, pulling the membrane inward and constricting the cell circumference to split the cytoplasm. The activity of this actin-myosin system is what physically pinches the cell membrane to create the dividing line, or furrow, between the two daughter cells.

Microtubules, while essential for organizing the mitotic spindle and helping position where the furrow should form, do not generate the constrictive force itself. Intermediate filaments provide structural support and resilience but don’t drive the membrane constriction. Ribosomes are involved in protein synthesis and are not part of the cytoskeletal machinery that generates the contractile force.