There are four known forces that are involved in evolution:

1)mutation,

2) genetic drift

3) gene flow or migration

4) selection.

TLS Online TPP Program

#Id: 9451

#XL - T Zoology

The extracellular domain of cytokine receptors are constructed of two subdomains, each contains seven conserved β strands folded together

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#XL - T Zoology

In cytokine receptors, 

the receptor and kinase are separate polypeptides, encoded by different genes, yet are bound tightly together.

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#Id: 9454

#XL - T Zoology

In cytokine receptors, the tightly bound kinase is known as a JAK kinase.

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#Id: 9455

#XL - T Zoology

Cytokine receptors are stably associated with one or two of the four known JAKs:

JAK1, JAK2, JAK3, and Tyk2

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Each members of JAK family of kinases contains:

An N-terminal domain that binds to the receptor

A C-terminal kinase domain 

A middle pseudokinase domain

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JAK kinases become activated after ligand binding and

receptor dimerization