Concept explainers
An Hfr strain with the genotype cys+leu+met+strS is mated with an F- strain carrying the genotype cys- leu- met- strR. In an interrupted mating experiment, small samples of the conjugating bacteria are withdrawn every
Medium
Medium
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a. What donor gene is the selected marker in each medium?
b. List all possible bacterial genotypes growing on each medium.
c. What is the purpose of adding streptomycin to each selection medium? The table on next page shows the number of colonies growing on each selection medium. The sampling time indicates how many minutes have passed since conjugation began
d. Determine the order of donor genes cys, leu, and met from the interrupted mating data.
e. Suppose a fourth selection medium containing leucine and streptomycin is prepared. At what sampling time do you expect the first-growing colonies to appear? Explain your reasoning.
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Genetic Analysis: An Integrated Approach (3rd Edition)
- An Hfr strain that is leuA+ and thiL+ was mixed with a strain thatis leuA− and thiL−. In the data points shown in the following graph,the conjugation was interrupted at different time points, and thepercentage of recombinants for each gene was determined bystreaking on a medium that lacked either leucine or thiamine.What information do you know based on the question and your understanding of the topic?arrow_forwardAn Hfr strain that is hisE+ and pheA+ was mixed with a strain thatis hisE− and pheA−. The conjugation was interrupted and the percentageof recombinants for each gene was determined by streakingon a medium that lacked either histidine or phenylalanine. Thefollowing results were obtained:It was found that hisE is 4 minutes away from pabB. The gene pheA was shown to be 17 minutes from pabB. Draw a genetic map describing the locations of all three genes.arrow_forwardThree different Hfr strains, derived from the same F strains (H), were mated with F- strains auxotrophic for a number of nutritional requirements (trp bio leu azi mal tyr gal ). Matings were interrupted at various intervals and cells were plated on minimal medium supplemented with particular nutrients to test for gene transfer. The following mapping data was obtained: Genes Hfr strains bio leu azi mal gal trp 17 tyr Hfr H Hfr 1 Hfr 2 Hfr 3 Hfr 4 25 4 10 10 18 3 5 9. 1 16 14 22 15 3 19 19 11 4 8 Draw a circular map of E. coli chromosome. Include distances (in minutes) between genes in your map and label arrowheads to show the origin of transfer for the five Hfr strains. (10arrow_forward
- Three different Hfr strains, derived from the same F* strains (H), were mated with F strains auxotrophic for a number of nutritional requirements (trp bio leu azi mal tyr gal ). Matings were interrupted at various intervals and cells were plated on minimal medium supplemented with particular nutrients to test for gene transfer. The following mapping data was obtained: Genes mal Hfr strains leu 25 trp 17 bio azi gal* tyr Hfr H Hfr 1 Hfr 2 Hfr 3 Hfr 4 4 10 10 18 3 9. 16 14 22 15 3 19 19 11 4 8 Draw a circular map of E. coli chromosome. Include distances (in minutes) between genes in your map and label arrowheads to show the origin of transfer for the five Hfr strains.arrow_forwardUsing bacteriophage P22, you performed a threefactor cross in Salmonella typhimurium. The crosswas between an Arg− Leu− His− recipient bacteriumand bacteriophage P22, which was grown on an Arg+Leu+ and His+ strain. You selected for 1000 Arg+transductants and tested them on several selective media by replica plating. You obtained the followingresults:Arg+ Leu− His− 585Arg+ Leu− His+ 300Arg+ Leu+ His+ 114Arg+ Leu+ His− 1a. What are the cotransduction frequencies of argwith either his or leu?b. Is arg closer to his than it is to leu, or is arg closerto leu than it is to his? What are the relative mapdistances?c. Why can you not obtain an accurate cotransductionfrequency for his and leu from the data provided?d. What is the order of the three markers?e. Draw the crossovers that would produce the classwith only one transductant.f. Estimate the proportion of the 4.9 Mb S. typhimuriumgenome that contains these three genes. Assume thatbacteriophage P22 can package the same amountof DNA as the…arrow_forwardDNA obtalned from the indicated donor strains is used to TRANSFORM the indicated recipient strains. The resulting progeny are plated on minimal medium so that only wild- type recombinants are scored. The number of wild-types for each cross is given in the chart below. What is the order of the genes? Donor Recipient wid type colonies a-b- c+ a+ b+ c- 273 a- b+ c- a+ b-c+ 462 a- b+ C+ a+ b-c- 2 a b- C+ a- b+ c+ O 4-b-c a-o-b b-a-c cannot be determined Question 18 of 26arrow_forward
- Three different Hfr donor strains are mixed with separate samples of an F− strain, and the following mapping data are provided from studies of interrupted conjugation: Appearance of genes in F − cells Hfr1: Genes b+ d+ c+ f+ g+ Time* 3 5 16 27 59 Hfr2: Genes e+ f+ c+ d+ b+ Time 6 24 35 46 48 Hfr3: Genes d+ c+ f+ e+ g+ Time 4 15 26 44 58 Construct a genetic map for these genes, indicating their order on the bacterial chromosome and the distances between them.arrow_forward5 strains of E. coli are isolated. They may be mutated on the ara, mal, leu and pro genes, and only these 4 genes. The 5 strains (E1 to E5) are tested on 5 different media and colonies are observed the next day. Rich Media (Lb) E5 E4 E1 E2Ⓡ E3 MM + Mal+Leu E5 E4 X ● E1 E5 X MM + Mal E4 X X E1 E3 E2 E5 ✪✪ E2 E4 ● E1 E5 MM + Mal+Leu +Pro E2 E3 MM + Ara E4 X X E1 E3 E2 X X Colonies are indicated by a black dot, absence of a colony is indicated by a cross. 1) Determine the genotypes of the 5 bacterial strains (E1 - E5)arrow_forwardA bacterium of genotype a+b+c+d+ is the donor in a cotransformation mapping. The recipient is a–b–c–d–. Data from the transformed cells are shown below. What is the order of the genes? a+ and b+ 2 a+ and c+ 0 a+ and d+ 5 b+ and c+ 5 b+ and d+ 0 c+ and d+ 0arrow_forward
- An Hfr strain that is hisE+ and pheA+ was mixed with a strain thatis hisE− and pheA−. The conjugation was interrupted and the percentageof recombinants for each gene was determined by streakingon a medium that lacked either histidine or phenylalanine. Thefollowing results were obtained:Determine the map distance (in minutes) between these twogenes.arrow_forwardA prototrophic strain (his" arg" lac') was used as a donor to transform an auxotrophic strain (his arg lac'). Initial transformants are isolated on minimal medium + histidine + arginine + lactose - glucose. i. What genotypes will grow on this medium? ii. These colonies are replicated to minimal medium + histidine, and 50% of the original colonies grow. What genotypes will grow on this medium? iii. The original colonies are also replicated to minimal medium + arginine, and 10% of the colonies grow. What genotypes will grow on this medium? iv. The original colonies are also replicated to minimal medium. No colonies grow. Based on this information, what genotypes will grow on minimal medium + histidine and on minimal medium + arginine? What is the relative gene order for his, arg, and lac? Which two genes are closer? Explain your answer.arrow_forwardGiven what we've discussed in class, what will be most likely outcome if you conjugate an streptomycin resistant ampicillin sensitive methionine auxotroph E. coli strain (engineered to be pir+) that is F- with a streptomycin sensitive non-HFR methionine prototroph strain that is F- and RP4+ but contains pUC18? Colonies on minimal media + ampicillin +streptomycin plates No colonies on minimal media +ampicillin +streptomycin platesarrow_forward
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