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Description: 1. Utilizing lactose operon, how can we explain how induction controls enzyme synthesis2. Use tryptophane operon and describe how levels of a key metabolite/tryptophane controls the gene function

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Utilizing lactose operon, how can we explain how induction controls enzyme synthesis 2. Use tryptophane operon and describe how levels of a key metabolite/tryptophane controls the gene function

Biology: The Dynamic Science (MindTap Course List)

4th Edition

ISBN:9781305389892

Author:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Publisher:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Chapter16: Regulation Of Gene Expression

Section: Chapter Questions

Problem 2TYK: For the E. coli lac operon, when lactose is present: a. and glucose is absent, cAMP binds and...

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1. How does induction control enzyme synthesis using lactose operon? 2. Describe how level of a key metabolite [tryptophane] controls the gene function using tryptophane operon
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.
For the E. coli lac operon, when lactose is present: a. and glucose is absent, cAMP binds and activates catabolicactivator protein (CAP). b. and glucose is absent, the level of cAMP decreases. c. activated CAP binds the repressor protein to remove it from the operator gene. d. the cell prefers lactose over glucose. e. RNA polymerase cannot bind to the promoter.
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.
. Recall that the trp operon has a special leader sequence (trpL) between the operator and the structural genes that offers attenuation as a mechanism for regulation of gene expression. (A) Draw a diagram of a trpL region of the operon when tryptophan is abundant in the cell.Label the following features: the DNA, 5’ and 3’ polarity of the RNA, the regions 1, 2, 3,and 4 and poly-U of the RNA, the pair of Trp codons (UGG), the ribosome, and RNA-Pol,along with any stem-loop structure that would form under these conditions (B) In the above example, will the rest of the trp operon genes be expressed? Briefly describe your reasoning why or why not (C) The trp codons in region 1 of the trpL gene have mutated to cysteines (UGG to UGC). What will be the effect on attenuation gene regulation of the trp operon? Brieflyexplain your reasoning.
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?
Using the lac operon as a model, explain the role of inducers, repressors, and inducer exclusion.
Like the lac operon, the hexose operon is controlled by a separate regulatory protein under the control of its own promoter (see the schematic of the operon below). The hexose regulatory protein is sensitive to fatty acyl CoA levels. When all hexose fuel sources are depleted, the bacteria switch to lipid metabolism and fatty acyl CoA levels increase. This turns expression of the hexose operon off. +1 +1 Regulatory Gene Pregulator P operon Hexose Operon Genes regulator promoter operon promoter
1. The table below shows partial diploid E. coli with lac operon mutations For each mutant, indicate whether expression of permease is:• None (absent)• Basal (on but low expression)• High (on and activated expression)when grown in either lactose only or glucose only media. Also indicate the cell’s overall growth phenotype (lac+ or lac-) when grown in lactose only and why you expect that phenotype (provide “why” for ONLY THREE of the mutants). ***Recall that a bacterial cell needs at least one functional copy of lacZ AND lacY expressed at high levels to producean overall growth phenotype of lac+ when grown in lactose only media. Lac Mutant CAP bindingsite Expression inlactose only Expression inglucose only Phenotype in lactose only I+ P+ O+ Z- Y+ / I- P+ O+ Z+ Y- WT Why?: Why?: Why?: Why?: Why?: I+ P+ O+ Z- Y- / I+ P- O+ Z+ Y+ WT Why?: Why?: Why?: Why?: Why?: I+ P+ O+ Z- Y+ / I+ P+ OC Z- Y+ WT Why?: Why?: Why?: Why?: Why?: IS P+ O+ Z+ Y- / I- P+ O+ Z+…
. Partial diploid forms of E. coli were created, each of which contained a com- plete lactose operon at its normal chromosomal site and the regulatory se- quences only (laci, P laco) on a plasmid. Predict the effect of each mutation on the activity of B-galactosidase before and after the addition of inducer. Use -, +, or ++ to indicate approximate activity levels. Briefly explain the basis for each of your predictions.
10. Think about the situation where there is an increased concentration of both glucose and allolactose in the media. Does this situation lead to the lac operon activation or not? Justify your answer? 11. Draw the structure of lac operon and its action when the following conditions are prevailing in the media: increased glucose, low glucose, higher c-AMP, low c-AMP, higher glucose, and high c-AMP, low glucose and High c-AMP, Higher glucose and higher allolactose? please assist with the above two questions
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?