Assuming that the level of glucose is low, a mutation in the repressor associated with the lac operon of E. coli which prevents binding of the repressor to lactose should result in: a. constitutive expression of the lac operon genes b. lack of expression or refuced expression of the lac operon genes under all circumstances c. expression of the genes only when lactose is present d. expression of the genes only when lactose is absent e. lack of expression of the lac operon genes, resulting in an increase in lactose production

Assuming that the level of glucose is low, a mutation in the repressor associated with the lac operon of E. coli which prevents binding of the repressor to lactose should result in: a. constitutive expression of the lac operon genes b. lack of expression or refuced expression of the lac operon genes under all circumstances c. expression of the genes only when lactose is present d. expression of the genes only when lactose is absent e. lack of expression of the lac operon genes, resulting in an increase in lactose production

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Description: 1. Assuming that the level of glucose is low, a mutation in the repressor associated with the lac operon of E. coli which prevents binding of the repressor to lactose should result in:a. constitutive expression of the lac operon genesb. lack of expre

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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4) Suppose you have an E. coli in which the gene that codes for the lac repressor protein has been mutated in such a way that the protein produced can bind to both lactose and DNA (at its specific binding site in the lac operon promoter) simultaneously. What effect, if any, would this have on regulation of expression of the lac operon? Briefly (1 sentence) explain why you would predict the effect or lack of effect this mutation would have.
Indicate whether each of the following statements about the lac operon are true or false: Bacteria with a lac phenotype are unable to use lactose because of some defect in expressing the genes A constitutive Lac+ phenotype could mean either that the production of repressor is defective or that the operator sequence is defective The lacl gene is next to, but is not part of, the lac 1. TRUE operon 2. FALSE Bacteria with a lac* phenotype cannot grow on media containing lactose as the only sugar The structural genes of the lac operon are each transcribed as a separate MRNA Expression of the Lac Repressor from the lacl promoter is regulated by lactose
1. The B-galactosidase gene of the lac operon is expressed at high level when which combination of following conditions is met? A. Select one answer for each of the following. Lactose concentration low high Lac Repressor Protein Inactive Active CAMP concentration low high Catabolite Activator Protein (CAP) Inactive Active B. Describe a mutation in a noncoding regulatory element that would result in constitutively high ß-galactosidase expression in the presence of both low glucose and low lactose. Explain its effect on gene regulation.
1. Draw a diagram of the lac operon. PO I+P+O+Z+Y+ I+P+OcZ+Y- I-P+O+Z+Y+ Lab section (circle): lacz gene lac Y gene lacA gene I+P+O+ZY/IPO+Z+Y- 2. The promoter (P) is the start site of transcription through the binding of RNA polymerase before actual mRNA production. Mutated promoters (P) cannot bind RNA polymerase, so no mRNA is made. In the table below, make predictions about the expression of ß-galactosidase and permease for different partial diploid (F') genotypes. Do this for E. coli growth on two different types of media - one without lactose, and one with. Use a to mark where there is no enzyme produced, and a + to mark where the enzyme is made. The first genotype has all wild-type alleles, and has been filled in as an example. Genotype IPOCZ+Y/I-P+O+Z-Y+ ISP+O+Z+Y/I+P+O+Z*Y* CR 1:00 Lactose absent B-galactosidase Permease R 3:-00 + R 6:30 Lactose present B-galactosidase F 10:00 Permease
a. What is the function of operons in bacterial gene regulation? b. Describe how a bacterial operon can be regulated by repressible proteins (such as the tryptophan operon). Include in your description both the “on” and “off” states of the operon. Key elements of your diagram should include: Co-repressor, Genes, mRNA, Operator, Operon, Promoter, Repressor, RNA polymerase.
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…
1. In E.coli transcription of the Lac Operon is known to be under Global control. For this operon explain the mechanisms of both negative and positive control (be sure to identify relevant regulatory molecules and operon regions). A. Positive Transcriptional Control: B. Negative Transcriptional Control: nodoubens besileroneD.8 2280019 pies8.) zenutost eupinUS C. If E.coli is grown in media containing both glucose and lactose when would you expect to see beta-galactosidase (catalyzes the hydrolysis of lactose) produced?
A mutation that inactivates transcription and translation from the regulatory gene of an inducible operon could result in: Group of answer choices A inactivation of RNA polymerase. B irreversible binding of the repressor to the operator. C three of these choices are correct D inhibition of transcription of the structural genes within the operon. E two of these choices are correct F transcription of the structural genes within that operon.
2. The lac operon controls the inducible expression of genes involved in lactose utilization. Several naturally occurring mutations have been discovered that affect how the lac operon operates. Consider the following mutations: I-= a mutation in the repressor protein that cannot bind the operator Is = a mutation in the repressor protein that cannot be removed from the operator Oc= a mutation in the operator that cannot bind the repressor Detail the functionality of the lac operon with following genotypes and cellular conditions (Note if there is no superscript, there is no mutation) Genotype I, O I, OC IS, O I, O Is, Oc Lactose present No No Yes Yes No Repressed (yes/no) N VAS ves NO Constitutive (yes/no) NO NO YES Yes NO Inducible (yes/no) Yes yes NO NO YUS
. The tryptophan operon is regulated by two methods. Describe in detail the regulation of the operon under conditions of low tryptophan levels in the cell.
. Mutants were isolated in which the constitutive phenotype of a missense lacI mutation was suppressed.That is, the operon was now inducible. These suppressor mutations mapped to the operon, not to the lacIgene. What could these mutations be?
Describe the probable genetic defect that abolishes the sensitivity of the lac operon to the absence of glucose when other metabolic operons continue to be sensitive to the absence of glucose.