10. Cell reproduction. Mitosis (M-phase). Cell cycle regulation – control systems.

Question 1

The cell cycle control systems

Answer 1

Control during G1 phase
-Restriction checkpoint G1
–Verification of cell replication potential
–Cells that will not progress to S phase begin to differentiate and enter G0
-DNA damage checkpoint - checks the state of the DNA

Control during G2 phase
-DNA damage checkpoint
-Unreplicated DNA checkpoint

Control during M phase
-Checkpoint for correct formation of mitotic spindle
-Checkpoint for the chromosome arrangement - controls the formation of metaphase plate.

Question 2

Cyclins and Cyclin - Dependent Kinases

Answer 2

Cyclins - cyclically fluctuating proteins in the cell
Cyclin-Dependent Kinases
-protein kinases that activate or inactivate other proteins.
-in the growing cells they are inactive
-to become active, they MUST attach to a cyclin - cyclin - dependent kinases, or Cdks.

MPF (M-phase-promoting factor)
-triggers the cell’s passage into the M phase, past the G2 checkpoint
-when cyclins that accumulate during G2, associate with Cdk molecules, the resulting MPF complex becomes active.