13. As you recall, a process called catabolite repression prevents high level of transcription of lacZYA genes when glucose is present in the growth medium. Low levels of glucose lead to production of CAMP, which enables CRP to bind to the lacZYA promoter. If the gene encoding CRP were to experience a loss-of-function mutation, what would be the expected outcome? a. Reduced level of lacZYA transcription in a medium containing only lactose (no glucose) b. No change in lacZYA transcription in a medium containing only lactose (no glucose) c. Increased level of lacZYA transcription in a medium containing only lactose (no glucose) e. Increased level of lacZYA transcription in a medium containing both lactose and glucose

13. As you recall, a process called catabolite repression prevents high level of transcription of lacZYA genes when glucose is present in the growth medium. Low levels of glucose lead to production of CAMP, which enables CRP to bind to the lacZYA promoter. If the gene encoding CRP were to experience a loss-of-function mutation, what would be the expected outcome? a. Reduced level of lacZYA transcription in a medium containing only lactose (no glucose) b. No change in lacZYA transcription in a medium containing only lactose (no glucose) c. Increased level of lacZYA transcription in a medium containing only lactose (no glucose) e. Increased level of lacZYA transcription in a medium containing both lactose and glucose

Human Anatomy & Physiology (11th Edition)

11th Edition

ISBN:9780134580999

Author:Elaine N. Marieb, Katja N. Hoehn

Publisher:Elaine N. Marieb, Katja N. Hoehn

Chapter1: The Human Body: An Orientation

Section: Chapter Questions

Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...

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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+…
Describe 3 ways by which transcription could be regulated (Hint 3 methods/tools/mechanisms that a cell can use to increase or decrease the amount of transcription, hint: Using a 1..... 2..... 3.....no part marks) A/
A. Identify the mutation(s) that lead to the most loss in transcriptional activity, and discusswhether those match expectations based on the consensus sequence for the Initiator.B. Hypothesize a molecular mechanism to explain how the mutations identified in Part Aresult in loss of transcription activity.C. Identify whether any mutations cause transcription to initiate from a different positionthan wild-type, and provide a brief explanation as to why that occurs for those mutantcore promoters. THIS IS A PRIMER EXTENSION ASSAY
1. Draw a simplified model of a cis-regulatory element with multiple trans-acting factors up-regulating gene expression. Your simplified model must include: a double-stranded DNA molecule labeled with its appropriate orientation (3' and 5', etc.), an area of DNA highlighting the gene of interest to be transcribed, a highlighted area showing the promoter region, one cis-regulatory element upstream of the promoter with its specific transcription factor • RNApol + a general transcription factor + a TATA binding protein all bound to the appropriate area (think about where these bind before transcription starts), an upstream enhancer with its transcription factor bound to it, • and finally the TSS. All parts must be labeled and in the correct area to earn full credit. **I suggest using different colors for this drawing problem**.
The E. coli lacZYA región will be transcribed at a rate greater than the low basal rate if: A. glucose and lactose are both present in the growth medium, but there's a defect in the cells ability to synthesize cAMP B. there is a defect in binding of the inducer to the product of the lacl gene C. glucose and lactose are both readily available in the growth medium D. the operator has mutated so it can no longer bind repressor E. none of the above
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 (0). 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* o* p* s 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…
Can you explain it?
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…
2. Below, recognition sites of two of these enzymes, Pstl and Nsil, are given 5'... CTGC AG. 3... GACGTC...5 3 Pstl recognition and cleavage site 5... ATGCAT 3'... TACGTA ... 5' 3' ... Nsil recognition and cleavage site a. Does cleavage by Pstl result in a 5' or 3' overhang? What is the sequence of this overhang? b. Does cleavage by Nsil result in a 5' or 3' overhang? What is the sequence of this overhang? c. Suppose you have a cloning vector that contains a Pstl recognition site and you also have foreign DNA that was cut with Nsil. Can this DNA be ligated into the Pstl site of the vector, and if so, explain its reason and draw the new ligation site. d. Can the new ligated DNA segment sequence be cut from the vector with Pstl or Nsil ? What potential problems do you see?
4.) Fully explain the role Gal3 has in the expression of galactose inducible (gal) genes.
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?
Q1: As illustrated here, at what control point is transcription regulated? Q2: What is a possible advantage of regulating gene expression before transcription, versus after? Q3: If you wanted to up-regulate production of the hemagglutinin protein in a tobacco plant carrying the hemagglutinin gene, at which control point(s) would that be possible? Justify your reasoning.