Formation
The formation of the primitive streak relies on a complex network of signaling pathways that work together to ensure that this process is highly-regulated. Activation of various secreted factors (Vg1, Nodal, Wnt8C, FGF8 and Chordin) and transcription factors (Brachyury and Goosecoid) adjacent to the site of streak formation is required for this process. In addition, structures, such as the hypoblast, also play an important in the regulation of streak formation. Removal of the hypoblast in the chick results in correctly patterned ectopic streaks, suggesting that the hypoblast serves to inhibit formation of the primitive streak.
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Famous quotes containing the word formation:
“Those who were skillful in Anatomy among the Ancients, concluded from the outward and inward Make of an Human Body, that it was the Work of a Being transcendently Wise and Powerful. As the World grew more enlightened in this Art, their Discoveries gave them fresh Opportunities of admiring the Conduct of Providence in the Formation of an Human Body.”
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“The formation of an oppositional world view is necessary for feminist struggle. This means that the world we have most intimately known, the world in which we feel “safe” ... must be radically changed. Perhaps it is the knowledge that everyone must change, not just those we label enemies or oppressors, that has so far served to check our revolutionary impulses.”
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“The moral virtues, then, are produced in us neither by nature nor against nature. Nature, indeed, prepares in us the ground for their reception, but their complete formation is the product of habit.”
—Aristotle (384–322 B.C.)