Genes in both prokaryotes and eukaryotes are regulated by activators and repressors.a. Compare and contrast the mechanism of functionof a prokaryotic repressor (for example, Lac repressor) with a typical eukaryotic repressor protein(a direct repressor).b. Compare and contrast the mechanism of functionof a prokaryotic activator (for example, CAP) witha typical eukaryotic activator protein.

Genes in both prokaryotes and eukaryotes are regulated by activators and repressors.a. Compare and contrast the mechanism of functionof a prokaryotic repressor (for example, Lac repressor) with a typical eukaryotic repressor protein(a direct repressor).b. Compare and contrast the mechanism of functionof a prokaryotic activator (for example, CAP) witha typical eukaryotic activator protein.

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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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. How do bacteria increase the efficiency of gene expression? Is this possible in eukaryotes? b. A mutation in the promoter of Gene K disrupts an enzyme binding site and results in the loss of Gene K expression. Is this change in gene expression likely happening at the transcriptional or the translational level? Explain. c. Propose three different mutations to prevent initiation, elongation, and termination of bacterial transcription, respectively. Explain how/why each mutation would prevent its respective step. (Hint: mutations can be in genes that encode proteins or regulatory DNA sequences)
Four terms and statements related to gene regulation in bacteria are listed below. Match the correct term to each of the four statements: Regulatory molecule that binds to operator region in DNA. 1. repressor Regulatory molecule that must be present at a site in DNA (such as promoter) so that transcription occurs. 2. Constitutive 3. Effector Small molecules that bind to regulatory molecule, such as repressor. 4. Activator Phenotype of I+ oCz*
E. coli has five genes that code for enzymes that make tryptophan. These genes are regulated by a single promoter and transcribed as one long gene. The presence of tryptophan shut down the production of tryptophan by the cell by binding to the repressor. This changes the repressors shape allowing it to bind to DNA operator, blocking RNA polymerase and cutting off the production of tryptophan. a. Describe what woud happen to the operon if some of the cells had a mutation on the repressor, not allowing it to bind with tryptophan. The repressor is described as an allosteric protein. What does this mean? b. Does the tryptophan model demonstrate an inducible or repressible operon? What is your evidence? *
Give the result(s) of the experiment in "MicroRNAs Control De Novo DNA Methylation Through Regulation of Transcriptional Repressors in Mouse Embryonic Stem Cell" and how the figure clearly demonstrates that outcome. Also, note the positive and/or negative controls for the experiment.
E. coli has five genes that code for enzymes that make tryptophan. These genes are regulated by a single promoter and transcribed as one long gene. The presence of tryptophan shut down the production of tryptophan by the cell by binding to the repressor. This changes the repressors shape allowing it to bind to DNA operator, blocking RNA polymerase and cutting off the production of tryptophan. a. Describe what would happen to the operon if some of the cells had a mutation on the repressor, not allowing it to bind with tryptophan. The repressor is described as an allosteric protein. What does this mean? b. Does the tryptophan model demonstrate an inducible or repressible operon? What is your evidence?*
(c) By binding one L-tryptophan molecule/monomer, the trp repressor binds to DNA to suppress syn- thesis of L-tryptophan in E. coli. Below is the amino acid sequence of the helix – (reverse) turn – helix region of the trp repressor that binds to DNA compared to the sequence of the corresponding DNA binding motif of the Prl protein, a different type of repressor protein. A diagram of the trp repressor dimer is also shown. reverse turn trp helix 4 70 Trp -Gly-Glu-Met-Ser-Gln-Arg-Glu-Leu-Lys-Asn-Glu-Leu-Gly-Ala-Gly- Ile- Prl -Ser-Glu-Glu-Ala-Lys-Glu-Glu-Leu-Ala-Lys-Lys-Cys-Gly-Ile-Thr- Val- Pri heilix trp helix 5 80 90 Trp Ala-Thr-Ile-Thr-Arg-Gly-Ser sgn-Ser-Leu-Lys-Ala-Ala- Prl Ser-Gln-Val-Ser-Asn-Trp-Phe-Gly-Asn-Lys-Arg-Ile-Arg- Prl helix
. a. How many ribosomes are required (at a minimum)for the translation of trpE and trpC from a singletranscript of the trp operon?b. How would you expect deletion of the two tryptophan codons in the RNA leader to affect theexpression of the trpE and trpC genes?
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 a.Which operons would be functional under these conditions? b.What repressors would be made? (NOTE: name the repressors using their gene names) c.Which repressor(s) would be made in the inactive form? d.Which repressor(s) would be made in the active form? e.Which repressor(s) under these conditions can bind the operator sequence? f.Which repressor(s)under these conditions cannot bind the operator sequence?
. In the tryptophan operon of E. coli, what happens when tryptophan levels get too high? tryptophan is removed from its co-repressor, causing it to detach from the operator tryptophan is removed from its co-repressor, causing it to attach to the operator tryptophan is bound to its co-repressor, causing it to detach from the operator tryptophan is bound to its co-repressor, causing it to attach to the operator all of the above occur at equal rates when tryptophan levels get too high
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
INTERPRET DATA Develop a simple hypothesis that would explain the behavior of each of the following types of mutants in E. coli. Mutant a: The map position of this mutation is in the trp operon. The mutant cells are constitutive; that is, they produce all the enzymes coded for by the trp operon, even if large amounts of tryptophan are present in the growth medium. Mutant b: The map position of this mutation is in the trp operon. The mutant cells do not produce any enzymes coded for by the trp operon under any conditions. Mutant c: The map position of this mutation is some distance from the trp operon. The mutant cells are constitutive; that is, they produce all the enzymes coded for by the trp operon, even if the growth medium contains large amounts of tryptophan.