3. The trp operon in bacteria is responsible for generating the enzymes responsible for the anabolic pathway through which tryptophan is synthesized. Two mechanisms are responsible for regulation of the operon. One is regulation of transcription initiation which involves repression by the trp repressor. The other is attenuation resulting in transcription termination, a process which involves the ribosomes. If you grow bacterial cells in conditions of low tryptophan abundance, indicate what you expect the effects to be on such regulatory mechanisms by answering the questions below. A) Will the operon be repressed by the trp repressor? Explain briefly. B) Will attenuation occur when the ribosome is translating proteins in this operon? Explain briefly.

3. The trp operon in bacteria is responsible for generating the enzymes responsible for the anabolic pathway through which tryptophan is synthesized. Two mechanisms are responsible for regulation of the operon. One is regulation of transcription initiation which involves repression by the trp repressor. The other is attenuation resulting in transcription termination, a process which involves the ribosomes. If you grow bacterial cells in conditions of low tryptophan abundance, indicate what you expect the effects to be on such regulatory mechanisms by answering the questions below. A) Will the operon be repressed by the trp repressor? Explain briefly. B) Will attenuation occur when the ribosome is translating proteins in this operon? Explain briefly.

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
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
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
2. Assume you have identified a new operon in bacteria (which you call the suc operon) that encodes enzymes required for catabolism of the sugar sucrose. The structural genes that are required to breakdown sucrose are transcribed from a promoter (Psuc). One of these enzymes is encoded by the sucS gene. Expression of the operon is controlled by a regulator, called SucR, which binds to an operator (O). Using your knowledge of the lac operon, interpret the results of the following experiments (Table 1) to propose a model describing how the sucrose operon might be regulated. Cell genotype Production of SucS enzyme Without sucrose With sucrose R* O* P* s* R O* p* s* ++ R* O P* S* -- RO* p* s* / R* Oʻ p* 5 R° O* p* S ++ -- ++ ++ Table 1. Production of SucS enzyme in various strains. “-" in the cell genotype indicates a loss of function mutation, “+" indicates wild type function, two genotypes separated by a / indicate a merodiploid or partial diploid. R° is a mutant version of SucR that…
5. Regulation of bacterial operons by inducers, e.g. lactose, exhibits which of the following properties? Inducer effect on RNA polymerase binding to the promoter Inducer binds to the Repressor produced by: repressor and: Activates the repressor A. Activates the repressor A separate gene Genes of the operon A separate gene Genes of the operon A separate gene Enhances В. Enhances Activates the repressor D. Inhibits the repressor Inhibits the repressor С. Inhibits inhibits Е. No effect 6. Gene transcription rates and mRNA levels were determined for an enzyme that is induced by a newly developed drug. Compared with untreated levels, drug treatment caused a 10x increase in the gene transcription rate and a 20× increase in both mRNA levels and enzyme activity. These data indicate that a primary effect of the drug treatment is to decrease which one of the following? A. The activity of RNA polymerase B. The ability of miRNA to act on mRNA C. The rate of translation D. The rate of binding of…
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.
As diagrammed below, some amino acid biosynthetic operons have stem loop structures in the mRNA. These structures play a role in the regulation of the operon by which of the following mechanisms? Translation stop codon- Attenuator loop. mRNA 5' 3' DNA attenuator trpE O Catabolite repressor protein can bind and prevent the hairpins from forming thus allowing translation to occur. O The leader sequence shown contains codons for the amino acid. When these are low, the ribosome stalls, allowing a hairpin between the two middle regions to form so that the rest of the message can be translated. In the presence of large amounts of the amino acid, the hairpin will wind around the amino acid and prevent further translation. O A repressor protein made of that amino acid will bind to the region and prevent translation when large amounts of the amino acid are present. O The uridine-rich region has codons for that amino acid; when present, this region will be a terminator region. The hairpins allow…
Match each of the following mechanisms with how it can change the levels of gene products--whether on different operons or within the same operon. Different promoters might have different DNA sequences Translation initiation sequences can cause different open reading 1. Differences in mRNA levels BETWEEN operons frames to be translated 2. Differences in protein levels WITHIN an operon differently. The secondary structures of MRNA can differ which can change the rate of degradation of transcripts.
1. Please tell me: What's a mutation in moleculer terms? 2. When a mutation deletes a base in genomic DNA, how does it affect the expression product production and reading frame? 3. How does induction control enzyme synthesis using lactose operon?
. 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?
28. Which statement does NOT explain why the lac operon would not be effectively regulated by an attenuation mechanism like the trp operon? 1.Lactose is a substrate for the lac operon protein products. 2.Products of lac operon enzymes are not used in protein synthesis. 3.Transcription and translation do not happen simultaneously for the lac operon. 4.Attenuation is a suitable regulatory mechanism for anabolic amino acid pathways. 5.All of these statements explain why regulation by attenuation would not be effective for the lac operon.
. 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