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Ch. 18 - Control of Gene Expression in Bacteria

Chapter 17, Problem 6

Predict what would happen to regulation of the lac operon if the lacI gene were moved 50,000 nucleotides upstream of its normal location.

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Welcome back. Here's our next problem. Which of the following factors will not affect the regulation of black op aran. Well, let's focus on the fact that we're looking for what will not affect the regulation of this operation. So keep track of that as we work through our answer choices. The first one choice A says absence of activator or repressor. Well, this cannot be our answer because it will definitely effect the regulation. Because this is the very mechanism by which the expression of the genes is regulated in the absence of lactose. The repressor protein sits on the operator. It blocks the promoter and prevents the expression of those black jeans. When the repressor protein is removed, the activator protein, which is activated in the absence of glucose, helps promote the transcription of the lack genes in large amounts. So the presence or absence of activators and repressors are the ways in which this opera is regulated. So it definitely affects its regulation. And it's not our answer choice B says distance of the lac L jeans from the regulatory elements with black jeans or the jeans for the repressor protein. And this does not affect the regulation of the opera. And it doesn't matter how far the gene for the repressor protein is the regulator elements. Because that gene is expressed, it generates the repressor protein and that repressor protein is diffused through the cytoplasm of the cell. So it doesn't matter how far away. Um it's binding site is it's floating around in the cytoplasm and can still bind to its site. So how far the gene for the repressor protein is does not matter and will not affect the regulation of the opera choice C says absence of RNA polymerase. Well, this definitely will affect the regulation if there's no RNA polymerase, the DNA cannot be transcribed into RNA and those proteins cannot be be made eventually. So, absence of RNA polymerase definitely will affect regulation and not our answer. And finally, Choice D. The leader of deletion of the promoter region. The promoter region is where are in a preliminary spines to generate that M. R. N. A. So with the promoter region, isn't there? You're not going to express those genes. So, Choice D. Will definitely affect the regulation of the opera. So again, which the following factors will not affect the regulation of the lac opera choice be distance of the laC L jeans from the regulatory elements. See you in the next video
Related Practice
Textbook Question

Activators bind to regulatory sequences in ________ and to ________ polymerase.

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Textbook Question

A regulon is a set of genes controlled by a. one type of regulator of transcription. b. two or more different alternative sigma proteins. c. many different types of promoters. d. glucose.

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Textbook Question

Evaluate these statements about regulation of the lac operon. Select True or False for each statement. T/F The lac operon is transcribed at the highest rate when extracellular glucose and lactose are abundant. T/F The repressor protein is bound to DNA of the operator when lactose is present. T/F A mutation in the operator is likely to prevent transcription of the lac operon under any condition. T/F A mutation that alters the catabolite activator protein is predicted to alter the regulation of many different operons.

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Textbook Question

Explain why it makes sense for the lexA regulatory gene of the SOS regulon to be expressed constitutively.

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Textbook Question

IPTG is a molecule with a structure much like lactose. IPTG can be transported into cells by galactoside permease and can bind to the lac repressor protein. However, unlike lactose, IPTG is not broken down by ββ-galactosidase. Predict what would occur to lac operon regulation if IPTG were added to E. coli growth medium containing no glucose or lactose.

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Textbook Question

In a mutant that lacks adenylyl cyclase, the enzyme that synthesizes cAMP, predict which of the following conditions of extracellular lactose and glucose would cause regulation of the lac operon to differ from that of wild-type cells. a. no lactose, no glucose b. no lactose, abundant glucose c. abundant lactose, no glucose d. abundant lactose, abundant glucose

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