mt2bier - EXAM 2 Developmental Neurobiology, BIPN144 May...

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Unformatted text preview: EXAM 2 Developmental Neurobiology, BIPN144 May 21, 2009 100 Points Total TA Question Graded Mimi 1 Teddy 2 Dileep 3 Beth 4 Alex 5 20 pts. 1. Define the term localized cellular determinant. 5 pts A molecule influencing cell fate that is asymmetrically distributed within a cell and is passed on to only one of its two daughter cells following cell division. Draw the lineage of an external sensory organ in the Drosophila peripheral nervous system (PNS). Indicate the following on your diagram: SOP cells, secondary precursor cells, neuron, glial cell, hair cell, socket cell. Also, indicate which secondary precursor cell receives the Numb protein. 5 pts 3 pts What cell fate defect is observed in the PNS of embryos lacking numb function? A transformation of the IIb cell fate to the IIa fate, which results in the loss of neurons and glia and production of extra hair and socket cells. 4 pts What signaling system does Numb influence, and what is the mechanism by which it exerts this effect? The Notch pathway. Numb binds to the intracellular domain of the Notch receptor and reduces its activity by preventing it from being cleaved and moving with Su(H) to the nucleus to regulate Notch target gene expression. 3 pts Do the two secondary precursor cells form an equivalence group? Are they equal? The IIa and IIb cells do form an equivalence group since both cells can give rise to either the neuron/glia or hair/socket progeny. They are not equal, however, since normally IIb is the one that receives numb and therefore becomes the signaling cell. 15 pts. 2. The sevenless and boss genes are required for formation of the R7 photoreceptor cell in the Drosophila eye....
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mt2bier - EXAM 2 Developmental Neurobiology, BIPN144 May...

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