M101A_2010Midterm1KEY - MCDB 101A W2010 Midterm 1 1/25/10...

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1 MCDB 101A W2010 Midterm 1 Name______ Key__ _________________________ 1/25/10 (100 points total) Perm #____________________________________ Multiple Choice: Circle the letter corresponding to the best answer (3 points for each correct answer). For all questions concerning cis and trans tests involving phage, assume that wild type control strains were assayed in parallel with the mutants and that controls yielded plaques as expected. 1. A mutant organism that requires the amino acid tryptophan in order to grow is known as a/an a. prototroph b. auxotroph c. heterotroph d. merozygote e. conditional mutant 2. Franklin’s X-ray diffraction studies directly provided which of the following information? a. The total length of a DNA molecule b. The length of each turn of a DNA molecule c. The antiparallel structure of the DNA molecule d. All of the above e. both b and c 3. rII mutations of bacteriophage T4 are examples of a. auxotrophic mutations b. conditional mutations c. host range mutations d. temperature sensitive mutations e. both b and c 4. What will be the result if a dominant host range rII mutation is included in the trans test? a. complementation will be seen b. the two mutations will appear to be in different genes c. no plaques will be observed when the mutant strains coinfect a nonpermissive host d. plaques will be observed when the mutant strains coinfect a nonpermissive host e. both a and d 5. DNA phosphatase is used in cloning experiments for the purpose of a. preventing self-ligation of vectors cut with a single restriction enzyme b. enhancing the activity of certain restriction endonucleases c. reducing the time required for ligation of the gene insert with the cut vector d. lysing bacteria to obtain plasmid DNA e. cutting DNA molecules 6. When mapping bacteriophage deletions, mutant phage strains are added pairwise to a permissive bacterial strain and the cell lysate is assayed for plaque formation when added to a nonpermissive bacterial strain. The absence of plaques in the lysate + nonpermissive strain step indicates a. The deletions in the two strains overlap each other b. The deletions in the two strains do not overlap each other c. Recombination has occurred between the two phage strains d. The mutations are located within the same gene e. Both a and c
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2 F C A 4 1 2 D 3 E B 5 7. A mutation in the epsilon subunits of DNA polymerase III would most likely lead to a. A deficiency in its polymerase activity b. A deficiency in its processivity c. A deficiency in its ability to terminate replication d. A deficiency in its 5’-3’ exonuclease activity e. A deficiency in its 3’-5’ exonuclease activity 8. A restriction endonuclease site that is 5 base pairs in length would be expected to occur once every a. 265 base pairs b. 1024 base pairs c. 4096 base pairs d. 625 base pairs e. none of the above 9. True or false : If the A+G/C+T ratio in one strand of a double stranded DNA molecule = 0.5, the
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This note was uploaded on 02/18/2011 for the course MCDB 101A taught by Professor Thrower during the Spring '08 term at UCSB.

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M101A_2010Midterm1KEY - MCDB 101A W2010 Midterm 1 1/25/10...

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