The prospective lens cells secrete paracrine factors that instruct the optic vesicle to form the retina. 

TLS Online TPP Program

#Id: 8605

#Unit 2. Cellular Organization

S phase Cyclin–CDKs

In human - cyclin A-CDK 2 

In budding yeast - CIb 5/6-Cdc 28

TLS Online TPP Program

#Id: 8606

#Unit 2. Cellular Organization

M phase Cyclin–CDKs

In human - cyclin A-CDK 1

cyclin B-CDK 1

In budding yeast - CIb 1/2/3/4-Cdc 28

TLS Online TPP Program

#Id: 8607

#Unit 2. Cellular Organization

Cdk1 

=Cdc2 (vertebrates and fission yeast)

= Cdc28  (budding yeast)

TLS Online TPP Program

#Id: 8608

#Unit 2. Cellular Organization

There are three D cyclins in mammals:

cyclins D1, D2, and D3

TLS Online TPP Program

#Id: 8609

#Unit 2. Cellular Organization

In free CDK2, the A-loop blocks access of protein substrates to the γ phosphate of the bound ATP.

TLS Online TPP Program

#Id: 8610

#Unit 2. Cellular Organization