BCH 5413 Exam 1 Questions And Answers

BCH 5413 Exam 1 t t t


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BCH 5413 Exam 1 Questions And Answers

1. The number of bases per turn of DNA is ____________ : ~10.5
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2. What does the Meselson and Stahl experiment confirm?: DNA replication is se
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mi-conservative

Heavy and light strands with nitrogen isotopes prove
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3. True or False t t


a. Most biological DNA is positively supercoiled.t t t t t


b. Triplex DNA is pyrimidine rich t t t t


c. Chargaff's rule: A=G &T=C t t t t


d. A single zinc finger can recognize 10bp of DNA: A.False, negatively = Left-
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handed. Some is right handed = positive t t t t t t


B.True t


C.False A=T C=G t t t


D.False, 3 bp, use multiple zinc fingers in a row for more sequence specificity/bp DNA is n
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t a uniform structure, many localized variants
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can substitute protein domains, alpha helix/beta hairpin, in zinc fingers to make hybrids w
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h different binding specificities (designated by alpha helix) for major grooves of DNA
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x-ray crystallography allows us to view and design custom designer DNA-
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binding proteins = alter gene fxn in intact cells
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4. In A & Z DNA: t t t t


a. Which is right handed helix? t t t t


b. Which one has 12bp per helical turn? t t t t t t


c. Which is the dehydrated form?: a.A t t t t t t


b.Z t


c. A t




primary DNA is B t t t


5. Gel electrophoresis: molecular separation technique c
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an separate nucleic acids or proteins
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1t/t24

, BCH 5413 Exam 1
t t t


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make AGAROSE gel with slots ho
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t liquid poured with "teeth"
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2t/t24

, BCH 5413 Exam 1 t t t


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put DNA in slot, run electric current at neutral pH
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DNA = negatively charged (phosphates) = migrates towards positive end key is fr
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iction

DNA stained with fluorescent dye, looked at under UV
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unknown DNA electrophoresed parallel with known to determine size t t t t t t t t




distance migrated = can plot on graph with log of molecular weights or number of bp
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ex: 20mm = 910bp t t t


6. PFGE = Pulsed Field Gel Electrophoresis: for longer sequences t t t t t t t t




as large as some chromosomes in yeast
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7. What is PAGE?: PolyacrylamideGel Electrophoresis u t t t t t t




sed for PROTEINS t t




have to denature the protein = treat with detergent, SDS, sodium dodecyl sulfate SDS
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-PAGE

SDS advantages: t


1) coats polypeptides with (-) charge t t t t


2) masks natural charge so results are purely based on molecular weight t t t t t t t t t t


8. What is 2- t t


D gel electrophoresis?: LESS POWER:use two different pH values to compare, pH af
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fects net charge so different rates of mobility
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2-
D = 1) proteins electrophoresed through narrow tube gel with pH gradients by ampholyte
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Once protein becomes neutral, no longer moves = isoelectric point
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2) gel removed from tube, placed at top of regular gel for SDS-PAGE
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9. What is Ion- t t


Exchange Chromatography?: usesaresintoseparatesubstances according to charg t t t t t t t t t t


e

(+) charged DEAE-Sephadex for anion-exchange (-
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) charged phosphocellulose for cation-exchange
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3t/t24