Which of the following statements can be made concerning the role of the lac repressor (Lac R) in conferring negative control of transcription of the lac operon? (mark all the correct answers) All of the other answers are correct. Lac R dimers bind to two distant operator sites to form a Lac tetramer, which is facilitated by DNA looping. More than one operator sequence is required for maximal repression by Lac R. Mutations in Lac R that prevent it from binding allolactose result in repression of the lac operon, even in the presence of lactose. A repression loop formed by the binding of LacR to two operator sequences is required for maximal repression by LacR.

Which of the following statements can be made concerning the role of the lac repressor (Lac R) in conferring negative control of transcription of the lac operon? (mark all the correct answers) All of the other answers are correct. Lac R dimers bind to two distant operator sites to form a Lac tetramer, which is facilitated by DNA looping. More than one operator sequence is required for maximal repression by Lac R. Mutations in Lac R that prevent it from binding allolactose result in repression of the lac operon, even in the presence of lactose. A repression loop formed by the binding of LacR to two operator sequences is required for maximal repression by LacR.

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Description: Which of the following statements can be made concerning the role of the lac repressor (Lac R) in conferring negative control of transcription of the lac operon?(mark all the correct answers) All of the other answers are correct.Lac R dimers bind to

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 9TYU: A mutation that inactivates the repressor gene of the lac operon results in (a) the continuous...

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A mutation that inactivates the repressor gene of the lac operon results in (a) the continuous transcription of the structural genes (b) no transcription of the structural genes (c) the binding of the repressor to the operator (d) no production of RNA polymerase (e) no difference in the rate of transcription
A mutation in the repressor LacI causes it to lose the ability to bind its effector, allolactose. What will be the effect of this mutation in the presence of allolactose (assume glucose is absent)? a) LacI cannot bind to the lac operator (lacO) and transcription of the lac operon is blockedb) LacI is permanently bound to the lac operator (lacO) and transcription of the lac operon is blocked c) LacI cannot bind to the lac operator (lacO) and transcription of the lac operon increasesd) LacI is permanently bound to the lac operator (lacO) and transcription of the lac operon increases
There is a mutation in sequence of the lac operator that prevents the lac repressor from being able to recognize and bind to it. What would the status of transcription of the lac operon be under each of the following circumstances? Explain your answers. a-Lactose present, glucose present b-Lactose present, glucose absent c-Lactose absent, glucose present d-Lactose absent, glucose absent
An 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 levels
When cAMP binds to the Catabolite Activator Protein (CAP), it causes a conformational change on the protein, which results in binding to the CAP-binding site on the DNA and ___________________________ of the lac operon. This conformational change induced by the binding of another molecule is known as a(n) _________________________________. transcription repression; binding effect translation; distortion effect mutation; interactive effect attenuation; compression effect transcription activation; allosteric effect
What experimental results would indicate that the mutation lacISlacIS is dominant to lacI+lacI+? In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in a repressed state in the absence of lactose. In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in a constitutive state in the absence of the repressor. In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in an activated state in the presence of lactose. In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in a repressed state in the absence of the repressor. In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in a repressed state in the presence of lactose.
Which of the following condition(s) is optimal for expression of the lac operon? I. low glucose and formation of CAP-cAMP complex II. high glucose resulting in no cAMP III. no lactose present and a functional repressor IV. presence of lactose binding to a functional repressor
How does the binding of the trp corepressor and the lac inducer to their respective repressor proteins alter repressor function and transcription in each case? What if there was a mutation in the operator region of the lac operon and the active repressor could not bind there? How would this affect the cell’s production of β–galactosidase? In general, Histone acetylation makes DNA ___________________, while DNA methylation makes DNA ________________.
A. A mutation is recovered in the gene that encodes the lactose operon repressor protein (LacI). Which of the following lac phenotypes would lead to the conclusion that the mutation causes an inability of the repressor to bind lactose? The lac structural genes would never be expressed. The lac structural genes would be expressed continuously. The lac structural genes would be expressed efficiently only in the absence of lactose. The lac structural genes would be expressed efficiently only in the presence of lactose. B. A mutation is recovered in the gene that encodes the lactose operon repressor protein (LacI). Which of the following lac phenotypes would lead to the conclusion that the mutation causes an inability of the repressor to bind Operator DNA? The lac genes would be expressed efficiently only in the presence of lactose. The lac genes would be expressed efficiently only in the absence of lactose. The lac genes would never be expressed. The lac genes would be…
How does the repressor protein contribute to selective expression of the structural genes Z, Y, and A in the lac operon? The repressor protein is only expressed when lactose is present. The repressor is always expressed. It blocks transcription when lactose is present. The repressor is always expressed. It allows transcription when lactose is absent. The repressor is always expressed. It blocks transcription when lactose is absent. The repressor protein is only expressed when lactose is absent.
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
The lac operon of E. coli controls the expression of genes that code for enzymes involved in lactose metabolism. Mutations to various regions of the lac operon have been discovered which affect both the control of gene expression and the function of the gene products. These mutations include: I - = produces a repressor protein that cannot bind to the operator region IS = produces a repressor protein that cannot be removed from the operator region OC = cannot bind a repressor protein Z - = produces a defective (non-functioning) β-galactosidase enzyme + = wild type Detail the functionality of the lac operon under the following genetic and cellular conditions. You do not need to consider the role of CAP in your analysis. Genes Repressed (yes/no) Constitutive (yes/no) IS O+ Z+ IS OC Z+