MCB121 MT1 Winter 2011

MCB121 MT1 Winter 2011 - Name_ MCB121 W11 Midterm 1 Page 1...

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Name______________________________ MCB121 W11 Midterm 1 FIRST MIDTERM January 25, 2011 Question Points Score 1 24 2 15 3 20 4 18 5 28 6 12 7 16 8 13 Total 150 This examination is closed book. There are 8 pages to the exam. Please count them before you start to make sure all are present . Please write your name on each page of the exam . Answer each question in the space provided. If additional space is required use the back of the page and indicate clearly that you continued your answer on the back. Do not attach additional pages. GOOD LUCK! Page 1 of 8
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Name______________________________ MCB121 W11 Midterm 1 1. (24 points) The packaging of DNA into nucleosomes gives 7-fold compaction relative to B-form DNA. The position and spacing of nucleosomes along DNA is also critical for gene expression. A. (6) Describe the protein components of a nucleosome including the number and stoichiometry of the subunits. H2A x 2, H2B x 2, H3 x 2, H4 x 2 B. (3) You want to set up an experiment where you assemble 10 nucleosomes on a single DNA molecule using purified histone proteins. From the choices below, what is the minimal length of DNA you would chose for this experiment? 1. 200 bp 2. 500 bp 3. 1500 bp 4. 3000 bp C. (15) For each set circle the chromatin type that would exhibit the highest packing ratio, i.e. most condensed (Circle one of each pair): 30 nm fiber or 10 nm fiber Euchromatin or Heterochromatin Metaphase chromosome or Interphase chromosome Nucleosome wrapped DNA or DNA loops attached to a scaffold DNA at the nuclear periphery or DNA in the interior of the nucleus Page 2 of 8
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Name______________________________ MCB121 W11 Midterm 1 2. (18 points) In 1953, a paper was published describing a model for DNA as a double helix written by Jim Watson and Francis Crick, based on X-ray data obtained by Roslyn Franklin. Watson and Crick noted that the structure of DNA suggested a mechanism for its replication. A. (4) What aspect of the DNA structure suggested a model for DNA replication? The structure of DNA is two antiparallel strands of DNA arranged in a double helix. The complementary base sequences allow for each strand to serve as the template to copy the information contained in of the other strand. B. (4) DNA replication of chromosomal DNA is semi-discontinuous. What is the meaning of this term? Replication occurs from 5' to 3', so on the 5' to 3' template strand, the replication occurs 5' to 3' in small fragments. On the 3' to 5' strand, replication occurs continuously. C. (4) DNA pol δ in combination with the sliding clamp protein complex exhibits high processivity. Define the term “processivity” in this context. A highly processive enzyme can bind its substrate and continue enzymatic function for long
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This note was uploaded on 04/06/2011 for the course MCB 121 taught by Professor Gasser during the Winter '09 term at UC Davis.

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MCB121 MT1 Winter 2011 - Name_ MCB121 W11 Midterm 1 Page 1...

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