Concepts of Genetics (12th Edition)
12th Edition
ISBN: 9780134604718
Author: William S. Klug, Michael R. Cummings, Charlotte A. Spencer, Michael A. Palladino, Darrell Killian
Publisher: PEARSON
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Textbook Question
Chapter 16, Problem 16PDQ
Both attenuation of the trp operon in E. coli and riboswitches in B. subtilis rely on changes in the secondary structure of the leader regions of mRNA to regulate gene expression. Compare and contrast the specific mechanisms in these two types of regulation with that involving short noncoding RNAs (sRNAs).
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The genes that encode the enzymes for arginine biosynthesis are located at several positions around the genome of E. coli, and they are regulated coordinately by a transcription regulator encoded by the ArgR gene. The activity of the Argr protein is modulated by arginine. upon binding arginine, Argr alters its conformation, dramatically changing its affinity for the DNA sequences in the promoters of the genes for the arginine biosynthetic enzymes. given that ArgR is a repressor protein, would you expect that ArgR would bind more tightly or less tightly to the DNA sequences when arginine is abundant? if ArgR functioned instead as an activator protein, would you expect the binding of arginine to increase or to decrease its affinity for its regulatory DNA sequences? explain your answers.
Arginine is one of the amino acids that serves as a building block for protein synthesis. Arginine
biosynthesis depends on the expression of the arg operon, which encodes ArgC (a reductase) and ArgB (acetylglutamate kinase). Which of the following statements regarding mutation of the arginine biosynthesis repressor ArgR is true?
O A 1-bp insertion in the argR gene would result in a mutant able to grow in the absence of arginine,
O A 1-bp deletion in the argB gene would result in a mutant unable to transcriptionally regulate the arg operon encoding argB.
O A 1bp insertion in the argC gene would result in a mutant able to grow in the absence of arginine.
O A 1-bp deletion in the argR gene would result in a mutant that represses the arg operon when grown in the presence of arginine.
None of the above.
In the galactose operon of Escherichia coli, a repressor, encoded by the galR gene, binds to an operator site, galo, to regulate the expression of three structural genes, galE, galT, and galK. Expression is induced by the presence of galactose in the media. For each of the strains listed, would the cell show constitutive, inducible, or no expression of each of the structural genes? (Assume that galR−is a loss-of-function mutation.)
galR− galo+ galE+ galT+ galK+
galR+ galoc galE+ galT+ galK+
galR− galo+ galE+ galT+ galK−/ galR+ galo+ galE− galT+ galK+
galR− galoc galE+ galT+ galK−/ galR+ galo+ galE− galT+ galK+
Chapter 16 Solutions
Concepts of Genetics (12th Edition)
Ch. 16 - Even though the lac Z, Y, and A structural genes...Ch. 16 - Predict the level of genetic activity of the lac...Ch. 16 - Prob. 1CSCh. 16 - Prob. 2CSCh. 16 - Prob. 3CSCh. 16 - HOW DO WE KNOW? In this chapter, we focused on the...Ch. 16 - Prob. 2PDQCh. 16 - Contrast positive versus negative control of gene...Ch. 16 - Contrast the role of the repressor in an inducible...Ch. 16 - For the lac genotypes shown in the following...
Ch. 16 - For the genotypes and conditions (lactose present...Ch. 16 - The locations of numerous lacI and lacIS mutations...Ch. 16 - Prob. 8PDQCh. 16 - Prob. 9PDQCh. 16 - Predict the effect on the inducibility of the lac...Ch. 16 - Erythritol, a natural sugar abundant in fruits and...Ch. 16 - Prob. 12PDQCh. 16 - Prob. 13PDQCh. 16 - Neelaredoxin is a 15-kDa protein that is a gene...Ch. 16 - The creation of milk products such as cheeses and...Ch. 16 - Both attenuation of the trp operon in E. coli and...Ch. 16 - Prob. 17PDQCh. 16 - Prob. 18ESPCh. 16 - In a theoretical operon, genes A, B, C, and D...Ch. 16 - A bacterial operon is responsible for the...Ch. 16 - A marine bacterium is isolated and shown to...Ch. 16 - Prob. 22ESPCh. 16 - Prob. 23ESP
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- Mutation in the regulatory gene in the lac operon results in the formation of an inactive repressor. List and explain the effect of such a mutation on the expression of the structural gene for lactose in E.coli?arrow_forwardThe streptolysin S toxin made by S. pyogenes is encoded by a 9-gene operon, sagABCDEFGHI. Thinking about what a 3-line diagram would look like for this operon, answer the following questions. Write numeric answers only. For example, if your answer is 6 promoters, write only 6. 1) How many promoters control the expression of these genes? 2) How many locations does RNA Polymerase bind to get full expression of these genes? 3) How many ribosome binding sites are needed for full protein expression? 4) How many start codons will be needed for full protein expression? 5) How many mRNA strands will be produced with full operon expression? 6) How many proteins will be produced with full protein expression? 1arrow_forwardThe lac operon consists of three structural genes, lacZ, lacY and lacA that are transcribed as a single polycistronic mRNA. The new lac strain of Escherichia coli are as shown below: P+O+Z+Y+A+// P+O+Z+Y+A¯ (i) Illustrate how lactose induces the gene expression in lac 1 $// I-. (ii) Explain the function of the lacP and laco in the bacterial operon.arrow_forward
- In the bacterium,Martian coli, it was discovered that the lac operon is positively regulated. Lactose, when present, binds to the regulatory protein A. The protein A-lactose complex then binds to the operator domain 0 and induces synthesis of lacZ+ and lacY+ MRNAS. a) What would be the most common phenotype of o- mutants in terms of lactose utilization? Explain your answer. b) What would be the most common phenotype of A- mutants? Explain your answer.arrow_forwardExplain the process of attenuation in the trp operon under the following conditions: (i) No tryptophan (ii) High tryptophan levelsarrow_forwardAnalyze the following genotypes of the Lac Operon in E. coli. In each case, determine whether Beta-galactosidase (enzyme that digests lactose) and permease (membrane channel that brings lactose into the cell) would be made in the presence or absence of lactose. For the purpose of this question, ignore glucose levels. Simply select 'YES' if the proteins are made or 'NO' if they are not . (Refer to the Lac Operon diagram for the meaning of the letters in the genotypes. Remember a "plus" superscript indicates normal functioning part of operon or repressor gene, a "minus" indicates loss of function, "OC" means "operator- constitutive", and "IS" means "super-repressor") Absence of Lactose Presence of Lactose Genotype В-gal Permease В -gal Permease IS pt 0 z+ Y-/ I† p+ 0C z¯ y+ It p+ 0C z+ y+/ I* P¯ 0 Z- Y It P 0C Z- Y+/ I¯ p* 0 z+ y It pt o z Y+/ I¯ p+ 0 z+ Yarrow_forward
- In the lac operon (below), how will expression of the genes lacZ and lacy be effect by a mutation in the repressor protein (encoded by lach) that prevents it from binding the operator sequence (lacO) in the absence of lactose? Explain the answerarrow_forwardDescribe the mechanism by which cAMP receptorprotein (CRP), the regulatory protein for catabolite repression, functions. Use the lactose operon as an example.arrow_forwardThe map of the lac operon is shown below. Consider the following examples that include both haploids and partial diploids and explain in each scenario whether the repressor can bind and regulate expression and whether or not the lac operon is expressed. For partial diploids the plasmid is indicated by the F’. I+ O+ Z+ Y+ / F’ I+ O+ Z+ Y+ I- O+ Z+ Y+ / F’ I+ O+ Z+ Y+ I- O+ Z+ Y+ I+ Oc Z+ Y+arrow_forward
- Describe the role of the CRP–cAMP complex in positiveregulation of the lactose operon in E. coli.arrow_forwardWhat would happen if the operator sequence of the trp operon contained a mutation that prevented the repressor protein from binding to the operator? (Explain what would happen in both the presence and absence of tryptophan)arrow_forwardExamine the following theoretical operon (gen) in E. coli which contains structural genes (genC, genB, genA) that are involved in amino acid biosynthesis. The gen operon also includes the gene encoding for the regulator molecule within it. When the amino acid that this operon helps synthesize is present, it binds to the regulator forming a complex which can bind to the operator region. Assume that the regulator molecule only binds to the operator in the presence of the amino acid. Question 1 Promoter Operator genC genB gen operon Regulator genA Transcription occurs when: A. The amino acid is not bound to the regulator, causing the regulator to bind to the operator. B. The amino acid is bound to the regulator, causing the regulator to bind to the operator. C. The amino acid is not bound to the regulator, causing the regulator to fail to bind to the operator. D. The amino acid is bound to the regulator, causing the regulator to fail to bind to the operator. E. The operon is…arrow_forward
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