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In the experiment of Figure 7.1, Lederberg and Tatum could not discern whether
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Genetics: Analysis and Principles
- Using the technique of interrupted mating, five Hfr strains were tested for the sequence in which they transmitted several different genes to an F- strain. Each Hfr strain was found to transmit its genes in a unique sequence, as follows (only the first six genes transmitted were scored). Hfr 1 F O P R S Q Hfr 2 R P O F G Y Hfr 3 Y X W Q S R Hfr 4 W Q S R P O Hfr 5 F G Y X W Q A. For each of the Hfr strains, state which donor-gene marker should be selected in the recipients after conjugation to obtain the highest proportion of recombinants that will be Hfr? Strain 1 Strain 2 Strain 3 Strain 4 Strain 5arrow_forwardIn a transformation experiment, donor DNA was obtained from aprototroph bacterial strain (a+b+c+), and the recipient was a tripleauxotroph (a-b-c-). What general conclusions can you draw aboutthe linkage relationships among the three genes from the followingtransformant classes that were recovered? a+ b- c- 180 a- b+ c- 150 a+ b+ c- 210 a- b- c+ 179 a+ b- c+ 2 a- b+ c+ 1 a+ b+ c+ 3arrow_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
- In the experiment of Figure shown, Lederberg and Tatum could notdiscern whether met+ bio+ genetic material was transferred to themet− bio− thr+ leu+ thi+ strain or if thr+ leu+ thi+ genetic materialwas transferred to the met+ bio+ thr− leu− thi− strain. Let’s supposethat one strain is streptomycin-resistant (say, met+ bio+ thr− leu−thi−) and the other strain is sensitive to streptomycin. Describe anexperiment that could determine whether the met+ bio+ geneticmaterial was transferred to the met − bio− thr+ leu+ thi+ strain orthe thr+ leu+ thi+ genetic material was transferred to the met+ bio+thr− leu− thi− strain. bio+ thr− leu− thi− strain.arrow_forwardA group of genetics students mix two auxotrophic strains of bacteria: one is leu+ trp+ his− met− and the other is leu− trp− his+ met+. After mixing the two strains, they plate the bacteria on minimal medium and observe a few prototrophic colonies (leu+ trp+ his+ met+). They assume that some gene transfer has taken place between the two strains. How can they determine whether the transfer of genes is due to conjugation, transduction, or transformation?arrow_forwardIn E. coli, four Hfr strains donate the following markers,shown in the order donated:Strain 1: M Z X W CStrain 2: L A N C WStrain 3: A L B R UStrain 4: Z M U R BAll these Hfr strains are derived from the same F+ strain.What is the order of these markers on the circularchromosome of the original F+?arrow_forward
- Why would it have been possible to utilize N14 in the original bacteria and only allow growing bacteria to access N15 to build new (F1) bacteria and get the same results as the original Meselson experiment?arrow_forwardWhat would be the expected distribution of centrifuged DNA (in the Meselson /Stahl experiment), using only the intact chromosomes of E. coli, by the second generation (the F2 generation)? 12.5% heavy-weight DNA, and 87.5% intermediate-weight DNA 25% heavy-weight DNA, and 75% light-weight DNA 87.5% light-weight DNA, and 12.5% intermediate-weight DNA 75% heavy-weight DNA, and 25% light-weight DNA 50% intermediate-weight DNA, and 50% light-weight DNA The above experiment would demonstrate which of the following DNA replication mechanisms? completely discontinuous DNA replication completely continuous DNA replication semi-conservative DNA replication completely dispersive DNA replication completely conservative DNA replicationarrow_forwardIn the Hershey–Chase experiment, the radioactive label 32P was present inside bacterial cells (i.e., in the pellet), whereas the radioactive label 35S waspresent outside bacterial cells (in the supernatant). What would the researchers have concluded had the reverse been true, that is, if the radioactive label 35S were inside the cells and the radioactive label 32P were outside the cells?arrow_forward
- Recombinant protein production by a genetically modified Escherichia coli strain is proportional to cell growth. Ammonia is used as a nitrogen source for aerobic glucose respiration. The recombinant protein has the general formula CH1,55O0,31N0,25, while that of the cellular biomass is CH1,77O0,49N0,24. The biomass yield from glucose equals 0.50 g/g, while the recombinant protein yield from glucose corresponds to 20% of the cell yield from substrate.a) How much ammonia is required? What is the oxygen demand? (b) If the biomass yield remains the same, what are the ammonia and oxygen requirements for a wild-type strain of E. coli, with cell biomass of the same elemental composition, but unable to synthesize the recombinant protein? (c) On an industrial scale, cultivation takes place in a continuous fermenter at 28°C and the desired recombinant protein production rate is 7 g/h. Since the viscosity of the culture broth is considerable, the energy input due to agitation cannot be neglected.…arrow_forwardIn a transformation experiment involving a recipientbacterial strain of genotype a- b-, the following resultswere obtained. What can you conclude about the locationof the a and b genes relative to each other? Transformants (%)Transforming DNA a+ b- a-b+ a+b+a+b- 3.1 1.2 0.04a+b- and a-b+ 2.4 1.4 0.03arrow_forwardYou mix two auxotrophic strains of bacteria; one is leu+ trp+ his– met– and the other is leu– trp– his+ met+. After mixing the two strains, you plate the bacteria on minimal medium and observe a few prototrophic colonies (leu+ trp+ his+ met+). To determine whether gene transfer has occurred through conjugation, transformation, or transduction, you design an experiment in which you place filters between the two strains to see if gene transfer occurs. You set up three treatments:-Treatment A No filter, allowing contact between the bacterial strains-Treatment B Filter that blocks cells, but allows viruses and DNA through the filter-Treatment C Filter that blocks cells and viruses, but allows DNA through the filter When you check the results of your experiment, you find prototrophic colonies have occurred following treatments A and B, but not following treatment C. You conclude that gene transfer occurred through... Answer Choices Available: A) Conjugation B) Transformation C)…arrow_forward
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