At slightly lower concentrations (intermediate concentrations), activin (about 100 molecules per cell) activated the Xbra gene and instructed the cell to become muscle.

TLS Online TPP Program

#Id: 8918

#Unit 2. Cellular Organization

Centralspindlin is a heterotetramer composed of two copies of the kinesin-6 motor protein MKLP1 and a dimer of a Rho GAP

TLS Online TPP Program

#Id: 8919

#Unit 2. Cellular Organization

MKLP1 is inhibited by 14-3-3 to ensures that the spindle midzone microtubules do not compact until the end of anaphase

TLS Online TPP Program

#Id: 8920

#Unit 2. Cellular Organization

During anaphase, when cyclin B-CDK1 activity is extinguished but Aurora and Polo kinases are still active, Aurora B phosphorylates MKLP1 and displaces the 14-3-3, allowing compact the spindle midzone.

TLS Online TPP Program

#Id: 8921

#Unit 2. Cellular Organization

At the same time, Plk1 phosphorylates the Rho-GAP component, to form an active Centralspindlin-Ect2 complex. 

TLS Online TPP Program

#Id: 8922

#Unit 2. Cellular Organization

Centralspindlin-Ect2 complex catalyzes activation of RhoA, leading to cleavage furrow formation and division of the cytoplasm to form two completely separate cells.

TLS Online TPP Program

#Id: 8923

#Unit 2. Cellular Organization

Surveillance mechanisms known as checkpoint pathways responsible for the extraordinarily high fidelity of cell division, ensuring that each daughter cell receives the correct number of accurately replicated chromosomes