Sonic hedgehog, is the major active factor in the ZPA. 

TLS Online TPP Program

#Id: 10551

#Unit 4. Cell Communication and Cell Signaling

The activation of RIPK1 kinase is a key decisive event that can initiate cell death by either apoptosis or necroptosis.

TLS Online TPP Program

#Id: 8792

#Unit 10. Ecological Principles

TLS Online TPP Program

#Id: 9557

#Unit 11. Evolution and Behavior

Where, though, do these hereditary variations come from?

This was the great gap in Darwin’s theory, and he never filled it. The problem was serious because, according to the prevailing belief in blending inheritance, variation should decrease, not increase.

TLS Online TPP Program

#Id: 1692

#Unit 4. Cell Communication and Cell Signaling

Recognition of Recombination Signal Sequence (RSS) by the RAG1/RAG2 enzyme complex.

TLS Online TPP Program

#Id: 8859

#Unit 2. Cellular Organization

During G1, 

cohesins associate with chromosomes by cohesin loading factors Scc2 and Scc4 and unloaded continuously by a cohesin associated complex Pds5 and Wap1 proteins.