706_F06exam1_key - Name 1 Answer Key 7.06 Cell Biology...

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Unformatted text preview: Name: ___________________________ 1 Answer Key 7.06 Cell Biology EXAM #1 September 26, 2006 This is an open book exam, and you are allowed access to books and notes but not computers or any other types of electronic devices. Please write your answers in pen (not pencil) to the questions in the space allotted. Please write only on the FRONT SIDE of each sheet. And be sure to put your name on each page in case they become separated! Remember that we will Xerox all of the exams. Good luck! Question 1. 25 pts __________ Question 2. 30 pts __________ Question 3. 20 pts __________ Question 4. 25 pts __________ Name: __ 7.06 _____________________ 2 Answer Key Question 1 (25 points) Your collaborator in the Brain and Cognitive Science Department provided you with a neuronal cell line carrying a GFP reporter. The expression of the GFP reporter decreases when cells are treated with Neuronal Growth Factor (NGF). Your collaborator also mentions that NGF signals through a re- ceptor tyrosine kinase pathway similar to EGF. You also obtain a cell line from your collaborator that, upon NGF treatment, only partially inhibits GFP expression. Upon sequencing the genome of this cell line you ¡nd out that the cell line carries a re- cessive point mutation that partially inactivates Ras. A. (4 points) Name four functions of Ras that when mutated could cause increased GFP expression in that cell line. Defect in SOS binding Defect in Raf binding Increased GAP binding Defects in membrane targeting Defects in GTP binding Defect in GDP release (And many more possibilities) B. (10 points) How would the following mutations affect GFP expression in the neuronal cell line car- rying this Ras mutation? Would they increase or decrease expression? A mutation in the extracellular domain of the NGF receptor that prevents NGF binding Increase A mutation that prevents receptor auto- phosphorylation Increase Loss of GAP function Decrease A mutation preventing Ras farnesylation Increase A mutation in Grb2 that binds unphosphor- ylated Y Decrease S => A mutation at position 529 of Raf Increase MEK with a S => D mutant in the Raf phosphorylation site Decrease Y185 => F mutation in MAP kinase. Increase A mutation that causes constitutive dimer- ization of the MAP kinase. Decrease Mutations in a phosphatase that normally antagonizes MAP kinase function Decrease Name: _ 7.06 ______________________ 3 Answer Key The identifcation oF a gene that is negatively regulated by a RTK signaling pathway is interesting and you want to identiFy more genes that show the same response to NG¡. C. (4 points) Propose and experiment that would allow you to identiFy all the genes that are inhibited by NG¡. I would perform a microarray experiment to identify all the genes inhibited by NGF. I would isolate RNA from NGF treated cells (untreated cells would serve as my control). After making cDNA from the RNA (using fluorescently tagged nucleotides), I’d hybridize the cDNA to a microarray chip....
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706_F06exam1_key - Name 1 Answer Key 7.06 Cell Biology...

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