The decline of MPF activity at the end of mitosis is due to a. the destruction of the protein kinase Cdk. b. decreased synthesis of Cdk. c. the degradation of cyclin. d. the accumulation of cyclin.

Verified step by step guidance

1. Understand the components of MPF (M-phase promoting factor), which consists of two subunits: cyclin and Cdk (cyclin-dependent kinase).
2. Recognize that MPF activity is crucial for cell cycle regulation, particularly for triggering the entry into mitosis (M phase).
3. Identify that the activity of MPF is regulated by the levels and availability of its subunits. The binding of cyclin to Cdk is necessary for MPF activation.
4. Acknowledge that the decline of MPF activity at the end of mitosis is crucial for the process of exiting mitosis and progressing to the next phase of the cell cycle.
5. Degradation of cyclin leads to the inactivation of CDK, resulting in a decrease in MPF activity necessary for the cell to exit mitosis.

Key Concepts

Maturation Promoting Factor (MPF)

Maturation Promoting Factor (MPF) is a complex of cyclin and cyclin-dependent kinase (Cdk) that plays a crucial role in regulating the cell cycle, particularly in the transition from G2 phase to mitosis. The activity of MPF is essential for the initiation of mitosis, and its levels fluctuate throughout the cell cycle, peaking during mitosis.

Cyclin Degradation

Cyclins are regulatory proteins whose levels rise and fall throughout the cell cycle. At the end of mitosis, cyclins are targeted for degradation, which leads to a decrease in MPF activity. This degradation is primarily mediated by the ubiquitin-proteasome pathway, ensuring that the cell cycle progresses correctly and prevents premature re-entry into mitosis.

Cyclin-Dependent Kinase (Cdk)

Cyclin-dependent kinases (Cdks) are a family of protein kinases that, when activated by binding to cyclins, phosphorylate target proteins to drive the cell cycle forward. The activity of Cdks is tightly regulated by the availability of cyclins and other mechanisms, such as phosphorylation and inhibitory proteins, which ensure proper timing of cell cycle events.