Concept explainers
Fifteen bacterial colonies growing on a complete medium are transferred to a minimal medium. Twelve of the colonies grow on minimal medium. a. Using terminology from the chapter, characterize the 12 colonies that grow on minimal medium and the 3 colonies that do not.
b. The three colonies that do not grow on minimal medium are transferred to minimal medium supplemented with the amino acid serine (min + Ser), and all three colonies grow. Characterize these three colonies.
c. The serine biosynthetic pathway is a three-step path-way in which each step is catalyzed by the enzyme product of a different gene, identified as enzymes A, B, and C in the diagram below.
Mutant 1 grows only on min
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Chapter 4 Solutions
GENETIC ANALYSIS: INTEGRATED - ACCESS
- A plaque assay is performed beginning with 1 mL of a solution containing bacteriophages. This solution is serially diluted 3 times by combining 0.1 mL of each sequential dilution with 9.9 mL of liquid medium. Then 0.1 mL of the final dilution is plated in the plaque assay and yields 12 plaques.What is the initial density of bacteriophages in the original 1 mL? Enter your answer to two significant figures ( for example: 1.1 * 10^2)arrow_forwardIn a nutrient medium that lacks histidine, a thin layer of agar containing ~109 Salmonella typhimurium histidine auxotrophs (mutant cells that require histidine to survive) produces ~13 colonies over a two-day incubation period at 37 °C. How do these colonies arise in the absence of histidine? The experiment is repeated in the presence of 0.4 μg of 2-aminoanthracene. The number of colonies produced over two days exceeds 10,000.What does this indicate about 2-aminoanthracene? What can you surmise about its carcinogenicity?arrow_forwardYou have several different media onto which you inoculated eight strains of yeast (A-H). The media include a rich medium, an unsupplemented minimal medium, and minimal media each supplemented with one vitamin. Of the yeast strains, one is a prototroph and seven are auxotrophs for a vitamin. After overnight incubation, the following results were observed (tan patches represent growth): D plate 1 (A) B DE F GH plate 5 plate 4 plate 6 Which plate contains an unsupplemented minimal medium? [Select] Which plate contains a rich medium? [Select] plate 2 Which strain is a prototroph? [Select] Strain E is an auxotroph for niacin. Which plate reveals this specific auxotrophy? [ Select] plate 3 plate 7 One strain is an auxotroph for both choline and pantothenic acid. Which one is this most likely to be? [Select]arrow_forward
- What will be the results of the following experiment with explanations: A. Gram-positive bacteria and Gram-negative bacteria were placed into 0.2% NaCl solution. B. Gram-negative bacterial isolate was placed into 0. 3% NaCl solution containing only Lysozyme enzyme. C. Gram-positive bacteria and Gram-negative bacteria were placed into 0.09% NaCl solution containing only Penicillin?arrow_forwardA bacterial culture is initially composed of 100 cells. After 1 hour the number of bacteria is 1.5 times the initial population. a. If the rate of growth is proportional to the number of bacteria present, determine the time necessary for the number of bacteria to triple. b. What is the time required for a culture with 1x106 of the same bacteria to triple? Explain your results. c. Under what conditions would the answers obtained in (b) be invalid?arrow_forwardTRY TO KEEP IN SHORT AND USE OWN WORD FOR THIS QUESTION You are studying a type of bacteria isolated from the acidic water runoff of a mining operation. You subject two batches of the same bacteria type to different environmental growth conditions. One batch is grown at pH 2, while the other is grown at pH 7. All other environmental parameters are kept identical between the two batches. You then collect their proteins and run a Western blot using an antibody that binds to a proton efflux pump protein (which actively expends energy to pump protons out of a cell). How would you characterize the information obtained in this experiment? What does it tell you, and why is that potentially valuable information?arrow_forward
- In your laboratory, you have an F− strain of E. coli that is resistantto streptomycin and is unable to metabolize lactose, but it can metabolizeglucose. Therefore, this strain can grow on a medium thatcontains glucose and streptomycin, but it cannot grow on a mediumcontaining lactose. A researcher has sent you two E. colistrains in two separate tubes. One strain, let’s call it strain A, hasan F′ factor (an F prime factor) that carries the genes that are requiredfor lactose metabolism. On its chromosome, it also has thegenes that are required for glucose metabolism. However, it is sensitiveto streptomycin. This strain can grow on a medium containinglactose or glucose, but it cannot grow if streptomycin is addedto the medium. The second strain, let’s call it strain B, is an F−strain. On its chromosome, it has the genes that are required forlactose and glucose metabolism. Strain B is also sensitive to streptomycin.Unfortunately, when strains A and B were sent to you, thelabels had fallen…arrow_forwardUsing a schematic diagram, summarize the following steps in preparing competent cells for transformation: Inoculate a single colony of E. coli into 5 ml LB broth and incubate overnight at 37°C with moderate shaking (250 rpm). Add 200 μl of the culture into 50 ml LB broth and incubate overnight at 37°C with moderate shaking (250 rpm) to an OD600 = 1.3 to 1.5. Aliquot culture into five 15-ml pre-chilled, conical tubes. Leave tube on ice 5 to 10 min. Centrifuge cells 7 min at 1,600 × g (3,000 rpm), 4°C. Pour off supernatant and resuspend each pellet in 10 ml ice-cold CaCl2 solution (50 mM CaCl2), perform resuspension very gently, and keep on ice. Centrifuge cells 5 min at 1,100 × g (2,500 rpm), 4°C. Discard supernatant and resuspend each pellet in 10 ml ice-cold CaCl2 solution. Keep resuspended on ice for 30 min. Centrifuge cells 5 min at 1,100 × g, 4°C. Discard supernatant and resuspend each pellet in 10 ml ice-cold CaCl2 solution. Dispense cells (250 μl) into pre-chilled, sterile…arrow_forwardWhat is the attached enzyme in this assay and its corresponding substrate? A. Horseradish peroxidase and OPD (o-phenylenediamine dihydrochloride) B. Horseradish peroxidase and PNPP (p-Nitrophenyl Phosphate, Disodium Salt) C. Horseradish peroxidase and TMB (3,3',5,5'-tetramethylbenzidine) D. Horseradish peroxidase and ABTS (2,2'-azinobis-3-ethylbenzothiazoleine-6- sulfonic acid)arrow_forward
- A unique aquatic plant was discovered from a lagoon in El Nido, Palawan. To determine the protein content of the plant, an adequate amount of the plant extract was acquired, and Bradford assay was performed. Determine the total protein concentration, in µg/mL, of the acquired plant extract. A bovine serum albumin (BSA) stock solution with a concentration of 250 µg/mL was used and mixtures with the following compositions and absorbance readings were prepared: Volume of BSA (mL) Volume of water (mL) Absorbance Tube # at 595 nm 1 0.00 2.00 0.000 2 0.20 1.80 0.112 3 0.40 1.60 0.225 4 0.60 1.40 0.318 5 0.80 1.20 0.432 6 1.00 1.00 0.551 The absorbance reading of the plant extract is 0.275.arrow_forwardA graduate student was assaying LD50 (lethal dose 50%) of two temperature-sensitive Francisella tularensis strains in HeLa cells (human cell line). Both strains can infect humans and cause fatal tularemia if untreated, but it is difficult to obtain LD50 values in human subjects. The data below shows LD50 (lethal dose 50%) values of the strains in human cell culture. Can you predict the more virulent strain of the two human pathogens? Francisella tularensis strain A: LD50 @ 20°C= 100; LD50 @ 37°C= 1000 Francisella tularensis strain B: LD50 @ 20°C= 1000 LD 50 @ 37°C= 100 O It is not possible to determine the virulence of the two strains as human pathogens from the provided data Strain A and strain B are equally virulent as human pathogens, as they average out in virulence. O Strain A is more virulent than strain A as a human pathogen. O Strain B is more virulent than strain A as a human pathogen.arrow_forwardA graduate student was assaying LD50 (lethal dose 50%) of two temperature-sensitive Francisella tularensis strains in HeLa cells (human cell line). Both strains can infect humans and cause fatal tularemia if untreated, but it is difficult to obtain LD50 values in human subjects. The data below shows LD50 (lethal dose 50%) values of the strains in human cell culture. Can you predict the more virulent strain of the two human pathogens? Francisella tularensis strain A: LD50 @ 20∘C= 100; LD50 @ 37∘C= 1000 Francisella tularensis strain B: LD50 @ 20∘C= 1000 LD50 @ 37∘C= 100 Group of answer choices It is not possible to determine the virulence of the two strains as human pathogens from the provided data Strain A and strain B are equally virulent as human pathogens, as they average out in virulence. Strain A is more virulent than strain A as a human pathogen. Strain B is more virulent than strain A as a human pathogen.arrow_forward
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