121 Midterm 2_09gBlKey

121 Midterm 2_09gBlKey - Name Key, Blue Last, First MCB121,...

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Name Key, Blue MCB121, Page 1 of 9 Last, First Gasser, Burgess MCB121 Feb. 24, 2009, Second Midterm Instructions: There are nine pages in this exam including the cover sheet, please count them before you start to make sure all are present. Write your name on each page of the exam. Write your answers in the space provided below each question. If you need more space use the back of the page and indicate clearly that you have continued your answer on the back. Do not use additional paper. Amino acid Abbreviations Amino acid Abbreviations Alanine Ala A Leucine Leu L Arginine Arg R Lysine Lys K Asparagine Asn N Methionine Met M Aspartic acid Asp D Phenylalanine Phe F Cysteine Cys C Proline Pro P Glutamine Gln Q Serine Ser S Glutamic Acid Glu E Threonine Thr T Glycine Gly G Tryptophan Trp W Histidine His H Tyrosine Tyr Y Isoleucine Ile I Valine Val V Question Value Score 1 8 2 16 3 12 4 16 5 21 6 15 7 26 8 36 Total 150
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Name Key, Blue MCB121, Page 2 of 9 Last, First Gasser, Burgess 1. (8) Radiolabeled pre-mRNA has been incubated with nuclear extract and ATP to carry out an in vitro splicing reaction. Three different precursors are used. The first (1) contains a mutation that abolishes interaction of the 5’ splice site with U1, the second (2) contains contains all sequences sufficient to promote splicing. And the third (3), contains a mutation at the 3’ splice site. a) (5) For letters a-e identify the name of the molecule that best describes the structure to the right: __ d __ spliced product __ a __ lariat intermediate __ c __ unspliced precursor __ b __ lariat intron __ e __ free exon 1 b) (3) Indicate which step(s) of splicing, if any (i.e. step 1 only; step 1 and step 2; or no splicing) has successfully occurred using the three different precursor substrates. 1. ___ no splicing _____ 2. ___ Step1 and Step 2 __ 3.____ Step1 _____ a. b. c. d. e. 1. 2. 3.
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Name Key, Blue MCB121, Page 3 of 9 Last, First Gasser, Burgess 2. (16) Provide a brief statement of why each of the statements below is false: a) Addition of the 7-me G cap and loading of splicing factors occurs co- transcriptionally. Following transcription termination, the transcript is exported from the nucleus and polyadenylated. Poly-adenlyation occurs in the nucleus prior to the transcript being exported b) The spliceosome cycle requires highly processive RNA helicase proteins to disrupt extensive RNA base pair interactions that occur between snRNPs, snRNPs and pre-mRNA and even RNA base pair interactions within a single snRNP. The spliceosomal helicases are not processive and unwind only very short base paired RNA duplexes that form during the spliceosomal cycle. c)
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This note was uploaded on 04/07/2010 for the course MCB 102,103,12 taught by Professor Segel during the Spring '10 term at UC Davis.

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121 Midterm 2_09gBlKey - Name Key, Blue Last, First MCB121,...

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