Conjugation-transduction+probs - BIOLOGICAL SCIENCES 101 DR...

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Unformatted text preview: BIOLOGICAL SCIENCES 101 DR. MARK SANDERS CONJUGATION PROBLEMS l. Mating is established between an Hfr strain and an F— strain with the following genotypes; Hfr thr+ leu+ glu+ ala+ gal+ ampS X F— thr— leu— glu- ala- gal- ampR a. What will be the constituents of the medium used to select exconjugants that have acquired the thr+ allele? b. Once you answer part a, think about the number of different plates that would be necessary to test donation of all possible genes. 0. A. graphic representation of the time of entry of each donor gene is shown below. Construct a genetic map based on time of entry and determine the distance (in minutes) between each gene. Frequency ("/o) 01 HI: genetic characters among SII’ exconyuganls Time (minutes) 2. The order of entry of' genes from four different Hfr donors is given below. The genes are listed in order of transfer with the first gene transfered is at the top of each list and the last gene transferred at the'bottom. Construct a circular map of the donor chromosome, showing the location and orientation of each F plasmid insert main 1_Z___3____é 0 R E 0 F H M G B M H x A E R C E A C R M B x H 1. In E. coli the abflity to utflize the sugar lactose, synthesize the amino acid methionine, and resist death by the antbiotic streptomycin is conferred by the alleles lac“, met‘, and SUE, respectively- Mutants for all three alleles Ge, Iac‘mefstrs) cannot tolerate streptomycin and require glucose and methionine in their growth medium- E- coli strains ABC and D are characterized by their sex (donors are “male”, recipients are 'temale') and their ability to grow in certain media as indicated below: DOES IT FORM A GROWTH IN MEDIA CONTAINING: CONJUGATTON STRAIN TUBE? lactose lucose met lucose me str lactose me str A yes yes yes yes no no 8 yes yes yes yes no no C yes yes yes yes no no D no no no yes yes no In separate experiments. male strains A B, and C are mated with strain D for 15 minutes; mating is then interrupted, and the resulting cells are checked for their ability to produce colonies-on the following nutrient plates: ARE GROWTH IN MEDIA CONTAINING: THESE CELLS MATING glucoseflr lucose me str lactose str lactose me str DONORS? A x D yes yes no no yes 8 x D no yes no no yes C'x D no . es no ' ' es no A ldentifythegenotypeofeach ' atthelAC,METandSTRlodand identifyeachstrainaseither ,F‘Jjoerr. (Hint:Determinethegenotypes fromthefirstdtartandconfinntherlasmidstahxstromthesecond). STRAIN A- ; STRAIN C: STRAIN B: STRAIN D: B. What allele does the F'strain donate? C. What allele does the W strain donate? D- What was the purpose of adding streptomycin to all the mating selection plates? BIOLOGICAL SCIENCES 101 DR. MARK SANDERS TRANSDUCTION PROBLEMS l. The following data were obtained by Charles Yanofsky in a 1959 study of the structure of the tryptophan operon region of E. coli. In your analysis of these data, take note of the fact that Yanofsky knew from other data that the cys gene was at one end of theap operon and that the genes of the operon all had to be on one side of cys. _ % Cotransduction Donor Recipient Selected ‘Unselected of Unselected Genotype Genotype Marker Marker Marker With cys+ M ’cys+upE+ cystrpE- cys+ trpE+ ' 63 cys+trpC+ cys-tIpC- cys+ upC+ 53 cys+upA+ cys-trpA- ' cys+ ' upA+ 46 cys+trpB+ cys-trpB- cys+ trpB+ 47 3. Determine the gene order of the 17p operon genes based on analysis of the cotransduction frequencies 2. A later transduction analysis of the trp operon using different donor and recipient genotypes was used to v ‘ y the map created by Yanofsky. This genotypes in tlus transduction analysis are; Donor cys+ trpC— trpB- X Recipient cys- trpC+ trpB+ The cotmnsduction data are; Recombinant Observed Genotypes . Enmm cys+ trpC— trpB- 139 cys+ trpC— trpB+ 18 cys+ trpC+ trpB+ 141 cys+ tibC+ trpB- __4. i 302 a. Do these data confirm or refute the gene order identified from analysis of the Yanofsky data? Explain. b. Explain the recombination events that have occurred to create each of the four classes. c. What are the cys-trpC and eys-trpB ootransduction frequencies? ...
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Conjugation-transduction+probs - BIOLOGICAL SCIENCES 101 DR...

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