Bacteriology 303- Todar- Exam 3- Spring 02

Bacteriology 303- Todar- Exam 3- Spring 02 - Bacteriology...

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Unformatted text preview: Bacteriology 303 ' ' Name E Third Examination . a Student ID. N April 23, 2002 ' _ ~ _ Instructions: Multiple choice. Each question has one correct answer. Circle the letter that ‘ corresponds to your answer choice. ' 1. The DNA codon AAA is transcribed into an mRNA codon A. AAA - - . ‘ B. CCC C. GGG D. Trr .@uuu 2. The tRNA .a'nticodon for the. RNA codon AAA is. ":3. CCC.- -. . - S . . A . : .- , a D. TIT- - - . ' - ' ® UUU - ' - . 3. The RNA codons GGAjand GGC encode forthe amino acid glycine. This is an example of ® degeneracy of the genetic code ' - V B. silent mutation (3. point mutation D. termination E. translation 4. Which of the following is the most likely event to occur during transcription and translatibn of a gene that has undergone a frame—shift mutation'eariy in the encoding sequence for a specific ‘ protein? . I - ' . . A. Transcription of the entire gene is blocked because RNA polymerase cannot bind to its - promoter in the gene. . , V B. Translation is bl0cked because ribosomes cannot bind to the transcript (mRNA) of the gene. C. Transcription is halted at the point of the mutation. D. Transcriptionis halted downstream of the point of the mutation. _ . A complete transcript (mRNA) of the gene is produced, but an error (terminator orsto‘p. ‘ codon) encountered during translation truncates.(shortens) the protein. ' ' - - " ~ 5. What is the: most likely phenotypic Consequence of a point mutation (e.g. base substitution) in a bacterial gene that encodes for a particular enzyme? _ _ . . A ~ ‘ A. No enzyme is produced. . B. ‘An enzyme is produced'with no change in primary-structure or activity. C. A truncated (shortened ) protein is produced which lacks enzymatic activity.’ . The enzyme produced has an altered primary structure and may or may not show any a teration‘in- activity. ' , , ‘ E. The enzyme produced exhibits no change in primary structure but has altered activity. ( ‘ '§9ican be isolated from- . taining arginine ' B. direct plating on medium without arginine " C. replica plating from a medium without arginine to a medium with arginine ‘ replica plating from a medium with arginine to a medium without arginine . two of the above 6. Arg' ’ ; 7. Arg+revertants (prototrophs)-could be isolated from a population of Arg' mutants by A. direct plating on medium containing arginine B. direct plating on medium without arginineg/ - V ‘ C.‘ replica plating from a medium without arginine to a medium with arginine D. replica plating from a medium with arginine toga medium without arginine v (9 two of the above. . - ‘ - 1' 8. The penicillin enrichment (penicillin selection) technique is useful when isolating ,auxotrophic mutants (for example'Trp' )‘ because penicillin I g - reventsthe growth-of wild‘type'bacteria but not mutants / . _ .. does notaffect eukar'yoticcells» ,. - ' - - y- . -» kills only‘the growing bacterial-cells, not- the Mutants in the population . increases the rate of mutation toward auxotrophy E. does not affect E. coil under the conditions of the procedure -9. An environmental scientist wants to determine if two chemicals, X and Y, are possible mutagens. The Ames Test is employed using a Trp' strain of Salmonella typhimurium. The following results are obtained: ' I NUMBER OF REVERTANT (Trp+) COLONlE-S Qhemical Control Plate est Plate’ x 38 I 231 Y , -42 208 x The conclusion from these results is: A. Xis a possible mutagen; Y is probably not a mUtagen . _ B. X is probably not avmutagen;.Y probably is a mutagen ' . . ~ ‘ - both X and Y are probable mutagens. * ' v D. neither X nor. Y are mutagens _ ‘ ' - E. none ofthe above g _ '. . g . .. 10. During the process of generalized transduction . cell to cell contact is required - . _ ~. , a defective phage (tranSducing particle) can. enclose and transfer any gene from the donor acterial chromosome V " ' _ C. the transfer of DNA is inhibited in the presence of DNAasé Tameka-mm D. the recipient must<be F' E. two of the above - 11. During the WWWMWmD 50““ 'f‘recipq‘fifiies‘ waste ' FW'LQ’» -A. lys'ogenic bacteriophages are required 4 B. only genes linked to the prophage DNA are transferred from a donor to recipient C. the prophages makes an imperfect excision from the bacterial chromosome before replicating and lysing the host cell W - . two ofthe above _ r . . all of the above ' - ' 12. Which of the following statements is true of the transformation systems of both Haemophjlus and Streptococcus? , - The transformation system is genetically-encoded by bacterial chromosomal DNA. « . Highly artificial treatment of cells, such as ex sure to high concentrations of divalent- cations, is an absolute requirement for transform 'on to occur. ' ' 4 - a C; Competence involves formation of membranous "blebs" in the Gram-negative outer membrane of the recipient. . " D. DNA from virtually any source is taken up by the recipient cells. - ' E. DNA enters the cell in a'lmembranous transformasome. 13'. ’ Resistance transferfactors (RTFs). in bacteria are A. insertion elements on the F factor = - - ' . - transmissible plasmids with genes that encode drug resistance a . . transposons that move from place to place. on the bacterial chromosome, _’ D. chromosomal genes forthe synthesis of antibiotics E. genetic factors that prevent the transfer of drug resistance among mating strains 7 14. Similarities between a Iysog’enic bacteriophage and the F factor in E. coli include " ‘-A. They are genetic elements that are replicated in the bacterial host“. ' B. They may contain genes removed from the bacterial chromosomew/ C. They may integrate into the bacterial chromosome. / ' . D. They may be transferred horizontally from'a donor to recipient during the processes of enetic exchange. all of the above 15. During replication of a lytic phage in'a susceptible bacterial cellthe early proteins translated from early phage mRNA are concerned with -' - A. attachment of the virus to its host cell , ' - B. entry of the phage nucleic acid into the host cell g) replication of the viral nucleic acid - . viral assembly . E. ' lysis of the host cell '1 2 .16. During thelreplication of a lysogenicphage in its specific host cell, the late proteins. are" concerned With . . A. transcription of virus DNA B. integration into host DNA C. replication of the virus nucleic acid , viral assembly and escape from its host Cell E. two of the above ‘ 17. The process of lysogenic conversion results in expression of a new phenotype by a bacterium when lyogenized by a particular bacteriophage excision cf-prophage from the bacterial DNA C. phage replication and lysis of the bacterial host cell D. transfer of genes for toxin production from one bacterium to an .other E. transduction between bacteria 18. Which one of the following strains of E. coli would able to conjugate with E. coli F' , Mefi, Arg" , Lac” to produce a recombinant that grows on minimal medium with lactose as a sole source of carbon? ' A. P“, Met”, Arg' , Lac+ B. P", Met’ , Argl', Lac+' , C. Hfr; Me’t’f'A'fgi‘j'Lfic' © Hfr, Met”, Arg‘l', Lac+ ~ E. Hfr, Math Arg” ,. Lac+ _ . ’19. Which. one of the-.fo'lloWing strains. of coll would be able to Conjugate- with ' _ ' , . E. ,coli' F‘ , Met” ,‘Arg‘, 81' to produce a recombinant that grows on minimal medium ' ' W A. F+., Met+, Arg‘l', 371' B. F+, Met",>Arg+, 31+ .0. Hfr, Met‘ , Arg‘ , 81+ Hfr._ Met’"; Arg", 81'. E. none ofthe above ' '20. Two strains of Salmonella typhimurium are mixed,‘ one which is erg, his ', cob and CMr ; I and the other which is cob: thi', and CMS. In order to determine if genetic recombination takes place between these organisms which of the media below would you plate the mixture of cells on in order to detect the recombinants? ' ~r . arg = arginine . cob = cobalamin .(vit B12) I his = histadine‘ ‘ thi = thiamin (vit B1) . I CM =_chloramphenicol (r = resistant; 's = sensitive) ‘ A. Glucose minimal medirimplus cob, [erg .' . B- , glucoseminimal medium plus cob, thi C. glucoseminimal medium plus cob, his: glucose minimal medium plus his, thi, CM glucose minimal medium plus cob,~ GM r we" ice. m2 ‘ 21. A molecular biologist extracts an ampicillin-resistant (ampr) plasmid. from atstrain of E. ‘ coli and a tetracycline-resistant (TCr) plasmid from a strain of S. aureus. Using restriction enzymes and DNA ligases, the plasmids are cut and then joined together and transformed into a strain of E. coli which is sensitive to the two antibiotics. In order to detect successful~ transformation and recombination, what medium should be used to detect the transformants?‘ A.- minimal medium with no supplements ' B. minimal medium plus ampicillin Durst?" TLC ‘ C.~ minimal medium. plus tetracycline @ minimal medium'plus ampicillin and tetracycline E. none of the above ? 22. A bacterial geneticist mixes 1 09 cells of E. 'coli strain A which requires lysine and is v ampicillin sensitive with 109 cells of strain B which requires phefnylalanine and tyrosine and is ampicillin resistant. In order to detect whether genetic recombination had occurred between e two strains it would. be best to grow the mixture of cells in ' a a $5 'minimalglucose medium plus ampitillin ‘ I - ‘ r » minimal glUcOsemedium plus‘ lysine and phenylalanine _ ‘ ‘- * * '- minimalglucose medium plus lysine and tyrosine - ' f D. minimal glucose medium plus phenylalanine,'tyrosine and _a'mpi’cillin E. minimal glucose medium with no supplements , xx ‘7. ‘ 23. In order to obtain a lysine revertant from strain A (above) the culture should be plated on -' A. minimal glucose medium plus ampicillin ‘ B. ,minimal glucose mediUm plus lysine and phenylalanine C. minimal glucose medium plus lysine and tyrosine ‘ I minimal glucose-medium plus lysine and ampicillin minimal glucose medium withno supplements 24. 5 x108 cells of each of two strains-of Salmonella typhimurium, ‘one which is cys‘ his" and TCr , and the other which is arg‘ met” and TCS, are mixed in a tube. After 30 minutes, the ‘ mixture is plated onto various media and the following results after growth are noted: Minimal medium (glucose plus inorganic salts): no colonies ~ _ . . b— rie 1, Minimal medium plus arg: 50 colonies ~ . oyé 3 i“ t 'Tb Minimal medium plus his: 5 Colonies - ' . _kag Minimal medium plus arg and TC: no colonies V r - OJ“ ' 4. Minimal medium plus arg, met and TC: 50 colonies . . ‘ ,2 5ny arg = arginine I. _cys =' cysteine his = histidine ' I met = methionine ' ' . - TCc= tetracycline (r = resistant; s = sensitive The results of the experiment suggest that _ A. Genetic recombination did not place between the two strains of bacteria. B. The rate of reversion to. cysteine prototrophy (cys+) is 10' 8 C. The rate of reversion to methionine prototrophy (met+) _is 10‘7 The frequency of mutation from TCs to TCr is approximately 10' 7 all of the above and 22 colonies on the plate containing a 10' Z dilution. What is the rate of recombination ‘ I between the two strains of bacteria? . _ . ' f x] , Genetic recombination has not occurred between the two strains of‘bacteria. 17w 3. :2); .-'B.1o-2 ’ ‘ ‘ we: ‘ a 10' 5 ' D. 10-7 7 25. The following experiment was done: 108 cells of strain 1 of a bacterium requiring the amino acid proline and the vitamin thiamine were mixed with 108 cells of strain 2 which requires the amino acids methionine and leucine. After 30 minutes incubation, the mixture ,E. Genetic recombination has occurred but the rate cannot be calculated from thevdata given. I Questions 26—28 referto the fellowing pathway for tiyptophan biosynthesis in E. coli. Enzymes. j; a, b, c,d .an‘de are enéoded by. the‘structural genes of the tryptophan (trp)j=opero'n” in ‘ ‘ E.coli. ~ “ ' I ' - -' -- -' ‘ ' I" ' _ . a ' ‘ b C Glutamine + Chorismate ------ --> Anthranilate ":"""> B- """ '7‘> C»'""> d . ".e , r. . ' ' ...... --.> D----V---->' Tryptophan ' 26. This pathwayis' regulated in E.,coli by the ,process(es) of A. feedback-inhibition v . . . ' ' B.~ Iendproduct repression L/ _ C. enZyme induction D. catabolite repression ® two of the above 27." Tryptophan is an allOsteric inhibitor‘(effector) of which enzyme(s) in‘ the pathway? @aonly ,- a ' C. eonly D. b, c, d, and e only. E. a, b, c, d, "and e ‘28. The synthesis of which enzyme(s) is repressed in the presence of tryptophan? A.-aonly. . -,_ .. - ' x " . ' ' -B. bonly g _ g” - . . '- C! e I, H . ‘ _ . . ‘ . D._ b, c, d,.a'nd e only @ a, b, c, d, and e 29. An operon is @V a series of genes regulated by a single operator B. a nucleotide region of DNA where transcription begins C. an allosteric protein that blOcks the binding of RNA polymerase to DNA D. a region of DNA that binds an active repressor E. two of the above ' - 30. The operator region of an associated operon .: codes for the synthesis of a repressor 4 "\ . is a nucleotide sequence that binds an active repressor protein C. bindsRNA polymerase at the beginning of transcription of an operon _ . D. 'is a nucleotide sequence of an RNA molecule which is not translated into protein E. none of the above ‘ » 31. .In the pathway of lactose utilization by E. coli, when the lac operon is induced A. the lac repressor is active and transcription of the lac operon does not occur I Q) the lac repressor is inactive and transcription of the lac operon does occur C. lactOse cannot be transported by the cells ' . ~ . D. lactose cannot be cleaved to enter glycolysis E. none of the above a ' 4 32. In the positive control of transcription of the lac operon (e.g.".catabolite repression) cyclic AMP is required for ‘ - ' .' A. activating the lac repressor B.‘ inactivating the lac repressor © activating'the-CAP protein _ D. inaCtivating the CAP protein E. two of the above .' 5 xx _' 33. In a repressible' operon (e.g. the trp operon), in the presence of the etfector (signal) * molecule, the repressor protein is G) active and can bind to the operator site B. active and cannot bind to the operator site " C. inactive and cannot bind to the operator site D. inactive and can bind to the promoter-site _ , . E. active thereby allowing RNA polymerase to transcribe the genes for that pathway \l 32¢ ...
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Bacteriology 303- Todar- Exam 3- Spring 02 - Bacteriology...

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