The graph below shows a growth curve of E. coli growing in a defined medium containing equal concentration of glucose and lactose. On the y-axis optical density provides a measure of cell number, higher optical density indicates greater cell number. OD (optical density) Time Based on your knowledge regarding regulation of the lac operon, the best explanation of these results is that... A. The bacteria are utilizing both sugars simultaneously. B. At early time points, inhibition of the lac repressor allows for lactose metabolism.

The graph below shows a growth curve of E. coli growing in a defined medium containing equal concentration of glucose and lactose. On the y-axis optical density provides a measure of cell number, higher optical density indicates greater cell number. OD (optical density) Time Based on your knowledge regarding regulation of the lac operon, the best explanation of these results is that... A. The bacteria are utilizing both sugars simultaneously. B. At early time points, inhibition of the lac repressor allows for lactose metabolism.

Biology (MindTap Course List)

11th Edition

ISBN:9781337392938

Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. Berg

Publisher:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. Berg

Chapter14: Gene Regulation

Section: Chapter Questions

Problem 13TYU: INTERPRET DATA Develop a simple hypothesis that would explain the behavior of each of the following...

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Suppose you have six strains of E. coli. One is wildtype, and each of the other five has a single one of thefollowing mutations: lacZ−, lacY−, lacI−, oc, andlacIS. For each of these six strains, describe thephenotype you would observe using the following assays. [Notes: (1) IPTG is a colorless synthetic molecule that acts as an inducer of lac operon expressionbut cannot serve as a carbon source for bacterialgrowth because it cannot be cleaved byβ-galactosidase; (2) X-gal cannot serve as a carbonsource for growth; (3) E. coli requires active lactosepermease (the product of lacY) to allow lactose,X-gal, or IPTG into the cells.] Colony color in medium containing glycerol as theonly carbon source and X-gal, but no IPTG.d. Colony color in medium containing high levels ofglucose as the only carbon source, X-gal, andIPTG.e. Colony color in medium containing high levels ofglucose as the only carbon source and X-gal, butno IPTG
. Suppose you have six strains of E. coli. One is wildtype, and each of the other five has a single one of thefollowing mutations: lacZ−, lacY−, lacI−, oc, andlacIS. For each of these six strains, describe thephenotype you would observe using the following assays. [Notes: (1) IPTG is a colorless synthetic molecule that acts as an inducer of lac operon expressionbut cannot serve as a carbon source for bacterialgrowth because it cannot be cleaved byβ-galactosidase; (2) X-gal cannot serve as a carbonsource for growth; (3) E. coli requires active lactosepermease (the product of lacY) to allow lactose,X-gal, or IPTG into the cells.]a. Growth on medium in which the only carbonsource was lactose.b. Colony color in medium containing glycerol as theonly carbon source, X-gal, and IPTG
The diagram below represents a hypothetical operon in the bacterium E. coli. The operon consists of two structural genes (A and B), which code for the enzymes “Aase" and "Base", respectively, and also includes P (promoter) and O (operator) regions as shown. A В When a certain compound (X) is added to the growth medium of E. coli, the separate enzymes "Aase" and "Base" are both synthesized at a 50-fold higher rate than in the absence of X. (X has a molecular weight of about 200.) Which of the following statements is true of the operon described above? The region of the A gene that codes for the carboxyl-terminal amino acid of “Aase" is near the left end of the A gene. The P region contains nucleotide sequences to which the RNA polymerase holoenzyme (including the o subunit) binds specifically but which the core enzyme does not recognize. The addition of X to the growth medium causes a repressor protein to bind tightly to the O region. The mRNA copied from this operon will be covalently…
Suppose that E. coli sustains a mutation in its gene for the lac operon repressor making the repressor ineffective. How would this mutation affect the bacterium's ability to catabolize lactose? Would the mutant strain have an advantage over the wild-type strain? Explain your answer. (Minimum 150 words, the document will be checked for plagiarism)
Strain ROFL4 has a premature stop mutation in the lacZ gene, resulting in a nonfunctional b-galactosidase. Otherwise all other parts of the operon are functional. Circle the least number of components for an F' plasmid that will restore normal regulation and function of the lac operon in the resulting partial diploid. (may need more than one) (a) lacI+ (b) lacO+ (c) lacP+ (d) lacZ+ (e) None, cannot be restored.
Answer this 3 part question: (MC) What is the function of lactose in regulation of the lac operon? 1. activates a repressor protein 2. activates an activator protein 3. inactivates a repressor protein 4. inactivates an activator protein Consider a bacterial strain with a lac operon Р. О Y A a) Mention which parts of the DNA region shown in the diagram encode for • Enzyme proteins? • Operator • Promoter • Repressor gene b) Where would the lac repressor be bound in a E. coli cell that is growing in ( • high lactose? No lactose
Indicate what protein(s) will bind the DNA in the lac regulatory region of E. coli given the following conditions and briefly explain why. Also, indicate if the operon will be "ON" or "OFF" 1. Both lactose and glucose are absent in the medium 2. Only glucose is present in the medium
Indicate what protein(s) will bind the DNA in the lac regulatory region of E. coli given the following conditions and briefly explain why. Also, indicate if the operon will be "ON" or "OFF" 1. Both lactose and glucose are present in the medium 2. Only lactose is present in the medium
a. The original constitutive operator mutations in thelac operon were all base changes in o1. Why doyou think mutations in o2 or o3 were not isolated inthese screens?b. Explain how a mutagen that causes small insertions could produce an ocmutation.c. Would a strain with one of the ocmutations described in part (b) and also a lacIS mutation be ableto make β-galactosidase either in the presence orabsence of inducer? Explain
You are growing E. coli in a laboratory in order to study their operons. The growth media you are using contains lactose, no glucose and no tryptophan. Using your knowledge of operons and their regulation, answer the following questions I really need a in depth epxplantion for the queshtions to make sure i understand the answers a.What effect does lactose have on the bacterial cell’s lac operon? b.What does the absence of glucose do to the bacterial cell? c.You now add tryptophan to the cell. What would happen to the bacterial cell and its trp operon? d.What kind of regulation does lactose provide to an operon’s repressor?
Suppose that E. coli sustains a mutation in its gene for the lac operon repressor such that the repressor is ineffective. What effect would this have on the bacterium’s ability to catabolize lactose? Would the mutant strain have an advantage over wild-type cells? Explain your answer.
Give all possible genotypes of a lac operon that produces, or fails to produce, β-galactosidase and permease under the following conditions. Do not give partial-diploid genotypes. Lactose absent Lactose present β-Galactosidase Permease β-Galactosidase Permease a. − − + + b. − − − + c. − − + − d. + + + + e. − − − − f. + − + − g. − + − +