Regulation of Cell Cycle

AP Biology· difficulty 3/5

The graph shows the parallel concentrations of mitotic cyclin (dashed) and active MPF (solid).

level MPF activity cyclin time

What best explains MPF activity dropping while cyclin already began declining?

  • A

    CDK levels rise sharply at anaphase

  • B

    Cyclin degradation by APC/C inactivates the CDK partner

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  • C

    ATP supply drops during mitosis

  • D

    MPF is independent of cyclin

Explanation

The Anaphase-Promoting Complex tags mitotic cyclin for destruction; loss of cyclin inactivates CDK1 (the kinase part of MPF), allowing exit from mitosis.

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