Biological Science (6th Edition)
6th Edition
ISBN: 9780321976499
Author: Scott Freeman, Kim Quillin, Lizabeth Allison, Michael Black, Emily Taylor, Greg Podgorski, Jeff Carmichael
Publisher: PEARSON
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Chapter 18, Problem 8TYU
Summary Introduction
To review:
The effect of the addition of the Isopropyl β-D-1-thiogalactopyranoside (IPTG) to the Escherichia coli growth medium containing no glucose or lactose on lac operon regulation.
Introduction:
The IPTG is a structure quite similar to the lactose molecule. It can be transported by the galactoside permease and is capable of binding to the lac repressor protein. Isopropyl β-D-1-thiogalactopyranoside (IPTG) is a molecule with structure resemblance to lactose. IPTG can be transported into cells by galactoside permease and can bind to the lac repressor protein. However, unlike lactose, IPTG is not broken down by β-galactosidase.
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Students have asked these similar questions
. In the lac operon of E. coli, if glucose levels increase while lactose levels decrease, what will happen in the regulation of genes controlling the enzymes needed to catabolize lactose?
the lac operon will be activated due to cAMP-assisted CAP binding to a site near the promoter
the lac operon will be activated due to CAP detachment from a site near the promoter
the lac operon will be repressed due to cAMP-assisted CAP binding to a site near the promoter
the lac operon will be repressed due to CAP detachment from a site near the promoter
all of the above
If an abnormal repressor protein could still bind allolactose but the binding of allolactose did not alter the conformation of the repressor protein, how would the expression of the lac operon be affected?
Under what conditions would you expect to see high levels of expression of the structural genes in the lac operon?
Group of answer choices
Lactose is absent and glucose is absent
Lactose is absent and glucose is present
Lactose is present and glucose is present
None of these
Lactose is present and glucose is absent
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, biology and related others by exploring similar questions and additional content below.Similar questions
- Imagine that a new strain of E. coli is discovered, and it contains the following novel genetic region including the lacI gene and the lac operon: *see image* Upstream of the promoter associated with the lac operon, there is a new operator element "Oν" (O-"nu"). This new operator has high sequence homology to O1, the DNA element that is bound with the highest affinity by the lac repressor. What would be the impact of this new genetic element regarding behavior of the operonin the absence (vs. the presence) of lactose and allolactose? Answer in terms of the protein levels of the lac repressor, as well as the proteins encoded by the genes lacZ/Y/A in the downstream region of the operon. Remember that proteins, once expressed/generated, will not persist forever, and that they have a natural lifetime (ending when they are degraded by the cell).arrow_forwardAn E. coli cell acquires a mutation in the gene that encodes CAP. The mutation affects the DNA-binding domain of CAP and ablates the ability of CAP to bind to the CAP site. Under which condition will the genes of the lac operon be transcribed at high levels? Glucose absent, lactose absent Glucose absent, lactose present Glucose present, lactose absent Glucose present, lactose present Under any of these conditions, the lac operon will not be transcribed at high levelsarrow_forwardLet’s suppose you have isolated a mutant strain of E. coli in which the lac operon is constitutively expressed. In other words, the operon is turned on in the presence or absence of lactose. One possibility is that the mutation may block the transcription of the lacI gene, thereby preventing the synthesis of lac repressor. A second possibility is that the mutation could alter the sequence of the lac operon in a way that prevents the repressor protein from binding to the operator. How would you distinguish between these two possibilities?arrow_forward
- In the lac operon, the lacZ gene codes for an enzyme called ____________, which catalyze the breakdown of the sugar __________ into monosaccharides. This enzyme can also hydrolyze the sugar analog ____________, which produces blue pigments following its breakdown. Since the lac operon is not always on the bacterial cells, we add the chemical ________ which prevents the lac depressor from binding to the operators, leading to constitutive expression of the operon.arrow_forwardIf glucose levels in the cell are high and lactose is available from the environment, what is the status of transcription of the lac operon genes? Explain your answer from both an evolutionary perspective and in terms of negative and positive regulation of the operon?arrow_forwardThe lac operon produces enzymes that allow the bacteria E. coli to metabolize lactose, it is in an inducable operon. When lactose is present, will the repressor protein attach or leave the operon? How would this effect the production of lactose producing enzymes?arrow_forward
- Suppose you are studying the regulation of a gene involved in the metabolism of two nutrients, Llamasin and Alpacalon, in bacteria. You are trying to determine if these nutrients act as inducers in their operons. The following data were collected from your experiments. Which of these operons is most similar to the lac operon? Explain. Nutrient Levels of nutrient in growth medium Level of transcription of genes in operon Llamasin low high high low Alpacalon low low high high Highlight one in green: Llamasin Alpacalon Explanation:arrow_forwardWhat are the effects of the following conditions on Lac operon of bacteria? Please do not forget to mention about the role of repressor, activator, RNA polymerase in each case. Glucose is absent and lactose is present Glucose is present and lactose is present Glucose is present and lactose is absentarrow_forward. What is the role of catabolite activator protein (CAP) in the lactose operon of E. coli? it prevents RNA polymerase from binding to the promoter when lactose levels are high it assists RNA polymerase in binding to the promoter when glucose levels are high it prevents RNA polymerase from binding to the promoter when glucose levels are low it assists RNA polymerase in binding to the promoter when glucose levels are low it prevents RNA polymerase from binding to the promoter when lactose levels are lowarrow_forward
- Let’s suppose you have isolated a mutant strain of E. coli in which the lac operon is constitutively expressed. In other words, the operon is turned on in the presence or absence of lactose. One possibility is that the mutation mayblock the transcription of the lacI gene, thereby preventing the synthesis of lac repressor. A second possibility is that the mutation could alter the sequence of the lac operator in a way that prevents lac repressor from binding to the operator. How would you distinguish between these two possibilities?arrow_forwardA mutant strain of E. coli has a premature stop mutation in the lacZgene, resulting in a non-functional b-galactosidase. Otherwise, all other parts of the operon are functional. Which component of an F' plasmid will restore normal regulation and function of the lac operon in the resulting partial diploid?arrow_forwardIn addition to observing similarities to the lac operon, you also notice that this gene is regulated via attenuation, similar to the trp operon. Based on this similarity to this model operon, you could state that ___________. Group of answer choices If a terminator loop forms in the DNA, the expression of the structural genes is halted. The formation of the terminator hairpin followed by a series of Uracil (UUUUUUU) functions similar to Rho-Independent termination to result in the stopping of transcription. The transcription of a leader sequence affects the translation of the structural genes. Never mind – all of these statements are true! Attenuation will be the primary means of transcriptional regulation, with a repressor used as a back up option.arrow_forward
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