quiz100[1] - 05/02/2008 Name: ______________________ 2008...

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Unformatted text preview: 05/02/2008 Name: ______________________ 2008 Biochemistry Quiz 10 Multiple Choice (13 questions: front and back of page, 2 points each except as noted) Identify the choice that best completes the statement or answers the question. Calculators are not required and not permitted for this quiz. 2. 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) is an herbicide that blocks oxygen evolution and photophosphorylation. Oxygen evolution can be restored by addition of a Hill reagent, an external electron acceptor. What is the target of DCMU? A. ferredoxin:NADP+ reductase which blocks reduction to yeild NADPH B. the Mn cluster in photosystem II which blocks water binding C. the QB site in photosystem II which blocks reduction of plastoquinone D. the plastocyanin site of photosystem I which blocks plastocyanin oxidation E. the QN site of cytochrome b6f which blocks oxidation of plastoquinol 3. Two cysteines within thioredoxin participate in activation of enzymes by reduction of disulfide bonds through a disulfide exchange reaction. How can labeled thioredoxin be used to identify these enzymes? A. thioredoxin with a Cys to Ser mutation forms a thioester bond with the enzyme B. thioredoxin transfers a radioactive 35S atom to the enzyme by disulfide reduction C. thioredoxin with a Cys to Ser mutation forms one disulfide bond with the enzyme D. thioredoxin forms two long-lived disulfide bonds with the enzyme E. thioredoxin with both Cys mutated to Ser binds irreversibly to the enzyme 4. Which is not one of the four conclusions refered to as "Chargaff's rules"? A. base composition does not change with age, nutrition or environment B. base composition is equally divided between bases: A=C=G=T C. base composition of cellular DNA follows the relations: A=T and G=C D. base composition of DNA varies from one species to another E. base composition is the same in DNA from different tissues of the same species 5. Which is not packaged within the viral capsid to enable replication of a virus within a host cell? A. double strand DNA B. single strand RNA C. single strand DNA D. unbranched oligosaccharides E. double strand RNA 6. What is the linking number (Lk) of a relaxed circular DNA with 1050 base pairs? A. 10 B. 100 C. 1050 D. 10.5 E. 0 1 Name: ______________________ 7. What is the linking number of supercoiled circular DNA ( = 0.05) with 1050 base pairs? Hint: = (Lk-Lk0)/Lk0 where Lk0 is linking number in the relaxed state. A. 95 B. 90 C. 110 D. 105 E. 100 8. Which is not a benefit of negative supercoiling in genomic DNA? A. unwinding the DNA to promote a replication eye B. unwinding the DNA to promote a transcription bubble C. compacting the DNA for transmission to daughter cells D. unwinding the DNA to promote left handed Z-DNA conformations E. increasing strain on the DNA to promote tetraplex structures at telomeres 9. In 1958, the Meselson-Stahl experiment proved which of the following models of DNA replication? A. progressive B. rolling circle C. conservative D. dispersive E. semiconservative 10. Which is not required for leading strand synthesis in replication of the bacterial DNA? A. DNA polymerase I B. subunit, sliding clamp, of DNA polymerase III C. DNA gyrase (DNA topoisomerase II) D. complex, clamp loader, of DNA polymerase III E. DnaB protein helicase 11. Which of the following is not required for the catalytic activity of DNA Polymerase? A. DNA template B. primer with free 3' hydroxyl C. magnesium D. deoxyribonucleotide triphosphate E. nicotinamide adenine dinucleotide 12. The Ames test utilizes a strain of Salmonella typhimurium that is unable to grow in the abscence of histidine. Why are colonies observed in the presence of a mutagen? A. the mutagen replaces the need for histidine in metabolism B. a mutation in a gene for histidine metabolism is back-mutated C. the mutagen induces expression of bacteriophage genes for histidine metabolism D. a mutation in a gene for acetate metabolism creates a new metabolic pathway E. a mutation in the gene of DNA polymerase III removes inhibition to replication 13. Which DNA repair or replication mechanism does not require DNA polymerase I?` A. nick translation of Okazaki fragments B. base excision repair by DNA glycolase and AP endonuclease C. 5' 3'exonuclease digestion of RNA primer D. nucleotide excision repair by UvrABC (excinuclease) E. mismatch repair by MutL, MutS and MutH 2 ...
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This note was uploaded on 05/28/2008 for the course CHEM 350 taught by Professor Lee during the Spring '08 term at SIU Carbondale.

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