The membranous myelin sheath that surrounds and electrically insulates many nerve cell axons is particularly rich in

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#Question id: 7207

#Unit 5. Developmental Biology

Which of the following statements is true about formation of the primitive streak ?

A. by the cellular dance mechanism, the cells came down the sides of the epiblast to undergo a medially directed intercalation of cells in the posterior margin where primitive streak forms.

B. Cellular dance is mediated by wnt planar cell polarity pathway in the hypoblast cells, at the posterior edge of the embryo.

C. The Wnt pathway activated by fibroblast growth factors (FGFs) produced by the hypoblast.

D. The Wnt planar cell polarity pathway activated by b-catenin produced by the epiblast.

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#Question id: 4935

#Unit 11. Evolution and Behavior

Which gas was least abundant in Earthʹs early atmosphere, prior to 2 billion years ago?

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#Question id: 32267

#Unit 2. Cellular Organization

Which of the following transport step is not performed by coated vesicles? 

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#Question id: 12074

#Unit 7. System Physiology – Animal

Which of the following tends to increase potassium secretion by the cortical collecting tubule?

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#Question id: 1299

#Unit 4. Cell Communication and Cell Signaling

Pectins and hyaluronic acid are both: