1.) What is the developmental consequence of grafting an extra a chick leg bud t
ID: 212293 • Letter: 1
Question
1.) What is the developmental consequence of grafting an extra a chick leg bud to the region of the normal limb bud on the final number of neurons that project into the hind limb region of the embryo? Why does this happen?
2.) What would you expect to happen if you removed the extracellular calcium from a culture of an epithelium in which intercellular adhesion was mediated by E-Cadherin. Why would this happen?
3.) What is the developmental consequence in terms of the fate of the EMS blastomere if Lef/Tcf repression is inhibited during early C. elegans embryogenesis?
Explanation / Answer
2) Cells adhere to each other and to the extracellular matrix through cell-surface proteins called cell adhesion molecules (CAMs), the transmembrane adhesion proteins. CAMs can be cell-cell adhesion molecules or cell-matrix adhesion molecules. Some CAMs are Ca2+-dependent, whereas others are Ca2+-independent.
The cadherins are the major CAMs responsible for Ca2+-dependent cell-cell adhesion in vertebrate tissues. Cadherins are expressed in both invertebrates and vertebrates. They are the main adhesion molecules holding cells together in early embryonic tissues. E-cadherins are involved in calcium-dependent cell–cell adhesion in both epithelial and embryonic stem cells. In culture, the removal of extracellular Ca2+ or treatment with anti-cadherin antibodies disrupts embryonic tissues and cadherins, E-cadherins are rapidly degraded by proteases in the absence of calcium ions and hence disrupts the embryonic development.
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