126 midterm practice key

126 midterm practice key - midterm practice I Multiple...

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1/29/09 midterm practice I. Multiple Choices 1. The structure that causes formation of neural tissue in an overlying germ layer is called the a. ectoderm. b. notochord. c. endoderm. d. neural crest. e. neural tube. 2. Which of the following statements about mutations of Sonic hedgehog and related genes is false ? a. They cause approximately 30 percent of stillbirths. b. They often result in a cyclopean (single) eye. c. They can lead to holoprosencephaly. d. They can transform granule cells, leading to medulloblastoma. e. They can transform basal epidermal cells, leading to basal cell carcinoma. 3. Neuroblasts a. give rise to neuronal precursor cells. b. are neurons that are slated to die or “implode” during development. c. are the most slowly dividing neuronal precursor cells. d. arise from symmetrical cell divisions. e. arise from asymmetrical cell divisions. 4. Which of the following does not play an important role in the establishment of axon tracts and in growth cone navigation? a. Cell adhesion molecules b. Extracellular matrix components c. Cytoskeletal proteins d. Synaptic vesicle proteins e. Second messenger systems 5. Neurotrophic factors a. ensure that the correct numbers of axons innervate each target cell. b. ensure that each axon innervates the correct number of target cells. c. are involved in the elimination of excess synaptic connections. d. influence the clustering of neurotransmitter receptors.
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126 midterm practice key - midterm practice I Multiple...

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