Cyclin and Cyclin-Dependent Cyclin and Cyclin-Dependent KinasesKinases

Mr. HunterMr. HunterAP / IB Biology AP / IB Biology

Hyde Park AcademyHyde Park Academy12/07/200912/07/2009

The Cell Cycle ClockThe Cell Cycle Clock• Cell Cycle control

molecules are responsible for the pace and sequential events of the cell cycle.

• These regulatory molecules are ________ of two main types.

• Some are protein kinases, ________ that activate or inactivate other proteins by phosphorylating them.

The Cell Cycle ClockThe Cell Cycle Clock

• Protein kinases give the go-ahead signals at the _____ and ______ checkpoints.

• The kinases are present in the growing cell, but they are mostly in an ________ form.

• To be activated a Kinase must be attached to another protein called a ________. Cyclins fluctuate in concentration within the cell.

• These complex of these two proteins are named Cdks or ____________

The Cell Cycle ClockThe Cell Cycle Clock• The activity of Cdk rises

and falls with changes in concentration of cyclin.

• The first Cdk complex that was first discovered is called ______, Mitosis promoting factor.

• It triggers the cell’s passage from the ______ checkpoint to _________

The Cell Cycle ClockThe Cell Cycle Clock

• Cyclins accumulate during G2 and bind with Cdk proteins, the resulting MPF complex initiates Mitosis by adding a ________group to a variety of proteins.

• MPF acts in the _________ stage of mitosis causing the nuclear envelope to fragment.

• After mitosis is initiated, MPF switches itself off by activating _________ proteolytic enzymes that decrease cyclin levels.

The Cell Cycle ClockThe Cell Cycle Clock• The noncyclic part of the

MPF, the Cdk, persists in the cell in the _________ form until it associates with new _______ molecules synthesized during interphase of the next round of the cell cycle.

• Scientist have discovered the involvement of at least three Cdks at the G1 checkpoint.