A scientist has discovered a strain of bacteria that can convert ethanol to pyruvate. When these bacteria are studied further, the scientist finds that they express two genes, C and D and that these genes are part of an operon (shown below) In studying these bacteria, you discover that the operon has two mutations (m1 and m2) that prevent gene expression. In order to study this operon further, you decide to concentrate on mutant strain 2. You introduce a wild-type operon into these mutant bacteria (i.e. an operon with fully functional regulatory and operon genes) to see if you can restore the operon's ability to make pyruvate. The following table summarizes your results Pry Y Prco Op D CD Cell Type No ethanol added Ethanol added Expression level of C & D Expression level of C & D Wild-type bacteria Low level High level Mutant strain 1 High level High level Mutant strain 2 High level High level Mutant strain 2 + Wild Low level High level type operon Using the information given above - match the statement with the correct term 1. the repressor of this operon is functional 2. the m1 mutation affects th v [ Select ] regulatory gene promoter sequence 3. the m2 mutation affects th coding sequence operator sequence

A scientist has discovered a strain of bacteria that can convert ethanol to pyruvate. When these bacteria are studied further, the scientist finds that they express two genes, C and D and that these genes are part of an operon (shown below) In studying these bacteria, you discover that the operon has two mutations (m1 and m2) that prevent gene expression. In order to study this operon further, you decide to concentrate on mutant strain 2. You introduce a wild-type operon into these mutant bacteria (i.e. an operon with fully functional regulatory and operon genes) to see if you can restore the operon's ability to make pyruvate. The following table summarizes your results Pry Y Prco Op D CD Cell Type No ethanol added Ethanol added Expression level of C & D Expression level of C & D Wild-type bacteria Low level High level Mutant strain 1 High level High level Mutant strain 2 High level High level Mutant strain 2 + Wild Low level High level type operon Using the information given above - match the statement with the correct term 1. the repressor of this operon is functional 2. the m1 mutation affects th v [ Select ] regulatory gene promoter sequence 3. the m2 mutation affects th coding sequence operator sequence

Biology 2e

2nd Edition

ISBN:9781947172517

Author:Matthew Douglas, Jung Choi, Mary Ann Clark

Publisher:Matthew Douglas, Jung Choi, Mary Ann Clark

Chapter16: Gene Expression

Section: Chapter Questions

Problem 9RQ: The a/a operon is an inducible operon that controls the production of the sugar arabinose. When...

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P₁0 ORF1 t₁ ORF2 ORF3 t₂ The diagram above illustrates an operon that is regulated by the RepR protein. O A small molecule, X, is needed to enable RepR to bind to the operator (O). When X is absent, which of the following statements is most accurate? O RNA polymerase binding to the P₁ promoter is unblocked Equal amounts of ORF1, ORF2, and ORF3 are made Expression of ORF2 and ORF3 is prevented by the terminator t₁ O Expression of ORF1, ORF2, and ORF3 is de- repressed
The symbols a, b, and c in the table below represent theE. coli lac system genes for the repressor (I ), the operator(O) region, and the β-galactosidase (Z), although notnecessarily in that order. Furthermore, the order inwhich the symbols are written in the genotypes is notnecessarily the actual sequence in the lac operon.Activity (+) or inactivity (−) of Z geneGenotype Inducer absent Inducer presenta- b+ c+ + +a+ b+ c- + +a+ b- c- - a+ b- c+/a- b+ c- + +a+ b+ c+/a- b- c- - +a+ b+ c-/a- b- c+ - +a- b+ c+/a+ b- c- + +a. Which symbol (a, b, or c) represents each of the lacgenes I, O, and Z ?b. In the table, a superscript minus sign on a gene symbolmerely indicates a mutant, but some mutant behaviorsin this system are given special mutant designations.Using the conventional gene symbols for the lac operon,designate each genotype in the table.
Read aloud V Draw Highlight 2. You are studying the regulation of the lactose operon in Escherichia coli, by measuring expression of the lacZ gene (i.e production of beta-galactosidase). (a) You identify several loss-of-function mutations in which lacZ is never expressed, in the presence and absence of glucose and lactose. What components of the lac operon could be mutated to produce this phenotype? List all possibilities. (b) You identify another loss-of-function mutation with the following expression pattern: Media + glucose - lactose + glucose +lactose - glucose - lactose - glucose + lactose lacZ expression Low Low High High What components of the lac operon could be mutated to produce this phenotype? List all possibilities.
Part A If E. coll bacteria are placed in an environment that contains both glucose and lactose, the regulation of the lac operon will allow which nutrient to be processed first? ONether will be processed in this environment O Both will be processed at the same time. Glucose O Not enough is known about the regulation of the lac operon to know which nutrient will be processed first Lactose Submit Request Answer
amount of protein / amount of mRNA 12 mm / ↑ A B time (minutes) 20 Bacteria were grown in culture. At various time points, substances were added or removed from the culture medium. To assay the effects of the substances on operon gene expression, samples of bacteria were collected at one-minute intervals and levels of specific proteins and mRNAs were determined. If the operon under investigation is a repressible operon, which arrow indicates the addition of a molecule that binds the repressor protein?
When referring to attenuation in the regulation of the trp operon it would be safe to say that, when there are high levels of tryptophan available to the organism, ________. tryptophan inactivates the repressor protein translation termination of the trp operon is likely the trp operon is transcribed at relatively high levels the ribosomes stall during translation of the attenuator region transcription termination at the attenuator region is likely
Answer as Directed. Below is the model of a lac operon. lac I lac Z с promoter operator lac Y lac A DNA +1 1. What are structural genes? Are the lac structural genes transcribed in the absence of lactose? 2. What is the role of the promoter and operator sites in the operon? 3. Is the repressor protein bound to the operator site in the absence of lactose? In its absence? 4. Under what nutritional circumstances (high or low glucose) is CAP bound to cAMP? 5. In the absence of lactose and the presence of glucose in the bacterial growth media, what proteins are bound to the lac control region? Is the operon being transcribed then? 6. In the presence of lactose and the presence of glucose in the bacterial growth media, what proteins are bound to the lac regulatory region? Is the operon being transcribed then? 7. In the presence of lactose and the absence of glucose in the bacterial growth media, what proteins are bound to the lac control region? 8. Why is it adaptive for a bacterium to not…
1. Complete the following table based on your lac operon simulations. Absence of lactose Presence of lactose B-galactosidase permease B-galactosidase permease I*P*O*Z*Y* Mututed ISP+O*ZY* I'P*O°Z*Y* I*P*O°ZY
The a/a operon is an inducible operon that controls the production of the sugar arabinose. When arabinose is present in a bacterium it binds to the protein AraC, and the complex binds to the initiator site to promote transcription. In this scenario, AraC is a(n). activator inducer repressor operator
Explain why (a) inactivation of the O2 or O3 sequence of the lac operon causes only a twofold loss in repression, and (b) inactivation of both O2 and O3 reduces repression ∼70-fold.
In the: Mutation of the regulatory region for a repressor protein in the lac operon. Explain: (a) What is the process affected? (b) What is the Effect on the process? (c) Does it affect prokaryotes, eukaryotes or both?
Answer as Directed. Below is the model of a lac operon. lac I lac Z с promoter operator +1 lac Y lac A DNA 1. In the absence of lactose and the presence of glucose in the bacterial growth media, what proteins are bound to the lac control region? Is the operon being transcribed then? 2. In the presence of lactose and the presence of glucose in the bacterial growth media, what proteins are bound to the lac regulatory region? Is the operon being transcribed then? 3. In the presence of lactose and the absence of glucose in the bacterial growth media, what proteins are bound to the lac control region? 4. Why is it adaptive for a bacterium to not express the genes that encode for that lactose utilization proteins when lactose is not available or when glucose is present? 5. Why is it adaptive for the structural genes for using lactose to be under the control of a single promoter, i.e., synthesize a polycistronic message rather than three monocistronic message?