Correct option is A
Correct Answer: (a)
Explanation: Cytokinesis normally initiates after mitotic exit, which requires degradation of mitotic cyclins. Stabilization of mitotic cyclins keeps CDK activity high and prevents proper transition from mitosis to cytokinesis. This delays contractile ring formation and furrow ingression, leading to defective or delayed cytokinesis. Hence, stabilization of mitotic cyclins impairs cytokinesis.
Information Booster
· Cytokinesis is tightly coupled to mitotic exit.
· Degradation of cyclin B is required for activation of cytokinetic machinery.
· Persistent CDK activity inhibits contractile ring assembly.
· Proper temporal regulation ensures chromosome segregation precedes cell division.
· Cell cycle checkpoints indirectly influence cytokinesis timing.
Additional Knowledge
Formin and myosin II activation are essential for actin filament assembly and contractile ring constriction, promoting cytokinesis rather than inhibiting it. Centralspindlin-mediated stimulation of RhoA and activation of RhoA by Rho-GEF are key positive regulators of cytokinesis that drive cleavage furrow formation. Therefore, disruption of cyclin degradation, not activation of RhoA signaling pathways, is the event most likely to cause delayed or defective cytokinesis.
