Sonic Hedgehog (Shh) is an extracellular signalling protein which modulates expression of a number of genes. The hedgehog protein binds to a transmembrane protein called Patched (Ptch). The binding of Shh stops Ptch from inhibiting another transmembrane protein called Smoothen (Smo). When Smo is active, it is able to induce the Gli transcription factors to being transcribing genes. While many of the genes regulated by Hh/Gli are known, further experiments with the Hh pathway continue to identify new genes.
Comments
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I like that you explained the function of Shh. You could even go into detail in explaining what Ptch and the Hh pathway's role is and how it comes into play even more.
Comment II
I would explain Ptch and Smo to give the all around picture of the paragraph