2011_Questions_Week_7_Answers - 2011 Week 7 Study...

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2011 Week 7 Study questions: 1. Do you think facial neural crest cells are specified or determined? Support your answer with evidence that both supports and refutes your hypothesis. -Cranial neural crest does not really fit neatly into either category. It must have some type of species-specific inherent deterination within it becaue of the quck and duail experiments that retain the characteristics of the donor beak. However, it is far from a determined tissue; it is patterned by interactions with both the ectoderm (where the intersection of Shh and FGF8 causes beak outgrowth) and the endoderm. 2. Which pharyngeal (or branchial) arch or arches gives rise to the facial structures? `Pharyngeal Arch 1. 3. Velocardial facial syndrome (also called DiGeorge Syndrome) is a genetic disorder with a complex range of symptoms. Patients typically have cardiac problems, facial defects, and cleft palates, and may also have immune system problems. The syndrome is caused by a deletion of 1.5 - 3 million base pairs on chromosome 22. This large deletion removes many genes, and it has been challenging to determine which ones are causing the syndrome. Using your knowledge of developmental biology, speculate on what might be the embryonic origin of this phenotype (i.e. cell type). Using this speculation, devise an set of experiments using a model organism that will allow you to identify candidate gene(s) in the deleted region that might be responsible for the disorder. -Pharyngeal arch-derived neural crest cells generate the vast majority of the face and the aortic arches, but the thymus, which is responsible for T-cell maturation in the immune system, is derived from the 3rd and 4th pharyngeal arch (not mentioned in class). Cranial neural crest defects, as mentioned in class, also cause cleft palate. Defects in pharyngeal-arch derived crest cells could explain this complex set of symptoms. One experiment to explore this would be to identify all the candidate genes in the deleted region, perform in situ hybridization on a vertebrate model system
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2011_Questions_Week_7_Answers - 2011 Week 7 Study...

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