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Concept explainers
The phage P1 is used as a generalized transducing phage in an experiment combining a donor strain of E. coli of genotype leu+phe+ala+ and a recipient strain that is leu-phe-ala-. In separate experiments, transductants are selected for leu+ (experiment A), for phe+ (experiment B), and for ala+ (experiment C). Following selection, transductant genotypes for the unselected markers are identified.
a. What compound or compounds are added to the minimal medium to select for transductants in experiments A, B, and C?
b. Selection experiment results below show the frequency of each genotype.
c. Determine the order of genes on the donor chromosome.
d. Diagram the crossover events that form each of the transductants in experiment A.
e. In experiment B, why are there no transductants with the genotype leu- ala+?
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Chapter 6 Solutions
GENETIC ANALYSIS: AN INTEG. APP. W/MAS
- In recombination studies of the rII locus in phage T4, what is the significance of the value determined by calculating phage growth in the K12 versus the B strains of E. coli following simultaneous infection in E. coli B? Which value is always greater?arrow_forwardAustin Taylor and Edward Adelberg isolated some new strains of Hfr cells that they then used to map several 200 mal+ genes in Escherichia coli by using interrupted conjugation. 150 In one experiment, the researchers mixed cells of Hfr strain AB-312, which were xyl* mtl* mal* met* and sensitive to phage T6, with F strain AB-531, which was xyl mtl mal met and resistant to phage T6. The 100 mt/+ cells were allowed to undergo conjugation. At regular intervals, the researchers removed a sample of cells and 50 met+ interrupted conjugation by killing the Hfr cells with phage T6. The F cells, which were resistant to phage T6, survived and were then tested for the presence of 0. 20 40 60 80 100 genes transferred from the Hfr strain. The results of this experiment are shown in the graph. Time of sampling (minutes) On the basis of these data, give the order of the xyl, mtl, mal, and met genes on the bacterial chromosome and the minimum distances between them in minutes. The origin of transfer is…arrow_forwardE. coli cells are simultaneously infected with two strains of phage λ. One strain has a mutant host range, is temperature sensitive, and produces clear plaques (genotype h st c); another strain carries the wildtype alleles (genotype h+ st+ c+). Progeny phages are collected from the lysed cells and are plated on bacteria. The following numbers of different progeny phages are obtained: Progeny phage genotype Number of plaques h+ c+ st+ 321 h c st 338 h+ c st 26 h c+ st+ 30 h+ c st+ 106 h c+ st 110 h+ c+ st 5 h c st+ 6 a. Determine the order of the three genes on the phage chromosome. b. Determine the map distances between the genes. c. Determine the coefficient of coincidence and the interferencearrow_forward
- Shown below are the complementation test results involving 4 independently isolated lethal mutants in a bacteriophage. Complementation was assayed by simultaneouly infecting bacteria with two phage strains, each with a different mutation, neither of which could alone lyse the cells. In the table below, a "+" indicates the strains complemented each other and therefore lysed open the bacteria. A "0" indicates no complementation and therefore no cell lysis occurred. Test pair Results 1___2___3___4 1,2 + 1 0 + + 0 1,3 + 2 0 + + 1,4 0 3 0 + 2,3 + 4 0 2,4 + 3,4 + Which mutants are in the same gene? . a. 2, & 3 b.1, 2, 3 & 4 c.1 & 4 d.1, 2 & 4arrow_forwardShown below are the complementation test results involving 4 independently isolated lethal mutants in a bacteriophage. Complementation was assayed by simultaneouly infecting bacteria with two phage strains, each with a different mutation, neither of which could alone lyse the cells. In the table below, a "+" indicates the strains complemented each other and therefore lysed open the bacteria. A "0" indicates no complementation and therefore no cell lysis occurred. Test pair Results 1___2___3___4 1,2 + 1 0 + + 0 1,3 + 2 0 + + 1,4 0 3 0 + 2,3 + 4 0 2,4 + 3,4 + How many genes are there? a. 3 b.1 c. 2 d. 4arrow_forwardTwo mutations that affect plaque morphology in phages (a− and b −) have been isolated. Phages carrying both mutations (a− b−) are mixed with wild-type phages (a+ b+) and added to a culture of bacterial cells. Once the phages have infected and lysed the bacteria, samples of the phage lysate are collected and cultured on plated bacteria. The following numbers of plaques are observed: Plaque phenotype Number a+ b+ 2043 a+ b− 320 a− b+ 357 a− b− 2134 What is the frequency of recombination between the a and b genes?arrow_forward
- By conducting conjugation experiments between Hfr and recipientstrains, Wollman and Jacob mapped the order of many bacterialgenes. Throughout the course of their studies, they identified severaldifferent Hfr strains in which the F-factor DNA had been integratedat different places along the bacterial chromosome. A sample of theirexperimental results is shown in the following table:Explain how these results are consistent with the idea that thebacterial chromosome is circular?arrow_forwardTwo mutations that affect plaque morphology in phages (a and b ) have been isolated. Phages carrying both mutations (a b) are mixed with wild-type phages (a* b*) and added to a culture of bacterial cells. Once the phages have infected and lysed the bacteria, samples of the phage lysate are collected and cultured on plated bacteria. The following numbers of plaques are observed: Plaque phenotype Number a* b* 2043 a* b- 320 a b* 357 2134 What is the frequency of recombination between the a and b genes?arrow_forwardYou are given two strains of E. coli. The Hfr strain is arg+ ala+ glu+ pro+ leu+ T s; the F− strain is arg − ala− glu− pro−leu− T r. All the markers are nutritional except T, which determines sensitivity or resistance to phage T1. The order of entry is as given, with arg+ entering the recipient first and T slast. You find that the F− strain dies when exposed to penicillin (pens), but the Hfr strain does not (penr). How would you locate the locus for pen on the bacterial chromosome with respect to arg, ala, glu, pro, and leu? Formulate your answer in logical, well-explained steps, and draw explicit diagrams where possible.arrow_forward
- In five Hfr strains, each of which was used to build a time-of-transfer map, the genes entered the recipient cells as follows: Strain 1: S L A C T F Strain 2: N P F T C A Strain 3: T F P N U Y Strain 4: S H Y U N P Strain 5: U N P F T C Which of the following represents a correct gene map of these results? N P F T S L A C H U Y S L A C T F P N H Y U C T F P N U Y H S L A T C A L S P N U Y H F U N P C A L S F T H Yarrow_forwardA researcher is studying the rII locus of phage T4. FourrII− strains are obtained: A, B, C, and D. In the first experiment, E. coli strain K(λ) is coinfected with two rII− strains simultaneously and the results are recorded. Infection with A and B phage = lysis occurs Infection with A and C phage = lysis occurs Infection with B and C phage = no lysis occurs Infection with B and D phage = no lysis occurs Infection with C and D phage = no lysis occurs In a second experiment, coinfections are performed first in E. coli strain B, then the progeny phage are used to infect E. coli strain K(λ). Progeny of A and B phage = plaques form Progeny of B and C phage = plaques form Progeny of C and D phage = plaques form Progeny of B and D phage = no plaques from Which conclusions are consistent with these data? Why? A) Strains A and B carry mutations in the same gene. B) Strains B and D both carry the same mutation. C) Strains B, C, and D carry mutations in the same gene. D)…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_forward
- Biology: The Dynamic Science (MindTap Course List)BiologyISBN:9781305389892Author:Peter J. Russell, Paul E. Hertz, Beverly McMillanPublisher:Cengage Learning
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