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Second Midterm Spring 2010 Answers

Second Midterm Spring 2010 Answers - The correct answers...

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The correct answers for the questions are given below the questions in bold text. The rationale for the answer is provided in italics following the answer in bold, this rationale is provided to help you understand why the given answer is the correct one. 1. Give 8 steps involved in gene expression. Redundant answers will receive no credit. (8pt, 1 point each) Any 8 of these were the best answers, however, we accepted many other answers that showed understanding of any of the numerous steps in gene expression. Chromatin remodeling Transcription initiation Transcription elongation Transcription termination mRNA splicing mRNA capping cleavage and polyadenylation mRNA export Translation initiation Translation elongation Translation termination mRNA degradation Protein degradation Histone modification 2. Fill in the blanks (6 pt, 1 each) : During inflammation, (1) SELECTINS are up-regulated on the surface of endothelial cells lining blood vessels. These molecules recognize (2) GLYCOPROTEIN molecules normally expressed on the surface of neutrophils. This (3) HETEROTYPIC - interaction enhances the cell-cell contact between the neutrophils and endothelial cells. This increased contact results in the activation of (4) INTEGRINS on the surface of the neutrophil through (5) INSIDE-OUT mechanism of activation. This activation facilitates the passage of neutrophils through (6) ADHERENS junctions between the endothelial cells to fight infection within the tissue. Question 2 was directly from the textbook, page 247. Specific reference to this process, and that this would be found in the textbook was made twice during lectures, once on March 10 th during the Selectin slide, then again on March 15 th when 2 slides were presented to discuss the process.
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3. You have isolated cells from a patient with a single mutation that results in a decreasedresponse in cAMP signaling. You want to characterize which part of the cAMP signalling pathway is impaired. Two extracellular signaling molecules that bind to separate GPCRs each lead to reduced levels of phosphorylated cAMP Response Element Binding protein (CREB) as compared to cells from normal patients. Supplementing the cellular medium with cell-permeable cAMP restores the levels of phosphorylated CREB to the same levels as normal patients. What protein is mutated in the patients? (3 pts) ADENYLYL CYCLASE (Why? 2 GPCRs with same effect means that the defect is not in a GPCR. cAMP directly restores PKA activity because CREB becomes fully active, so PKA is normal, but is not getting enough cAMP. Adenylyl cylcase is the last possibility between GPCR and PKA). 4. In cells from a patient with a decreased PKC response, you try to characterize the defect in a similar manner to question 3. Two independent ligands that activate conventional PKC through a GPCR lead to a reduced level of activate PKC protein as compared to cells from normal patients. Calmodulin dependent protein kinase levels are stimulated equivalently to
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Second Midterm Spring 2010 Answers - The correct answers...

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