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Ch. 18 - Control of Gene Expression in Bacteria

Chapter 17, Problem 15

What characteristic of the light-producing regulatory circuit is consistent with the idea that it may be a regulon? What characteristic of this circuit stretches the definition for a regulon?

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Hello everyone. Here's our next question. It says the blank opteron encodes genes responsible for the self regulation and the production of proteins associated with light production or luminescence. Our choices are a lack B lux C. Trip or D sigma. We're thinking about the opera on for genes involved in luminescence that's going to be the choice. Be the lux opera on lux is latin for light. That's why that's the name there. But let's just look through our other choices. Um So we understand why they're not correct choice. A The lack opera is the operation for genes in bacteria that allow the bacteria to metabolize lactose. Thus its name allowing table is um of lack tous okay so that's obviously not our answer there. And the trip opteron is also in bacteria opera. And for genes involved in the synthesis of the amino acid tryptophan and then finally sigma assume it's related to the sigma factor. That's a general transcription factor and bacteria. Oops. And it enables specific binding of RNA polymerase two gene promoters. So this is not for a specific set of genes. Um You need this too involved in all the synthesis of all genes in bacteria because it allows RNA polymerase to bind to the gene promoters of any gene. So that's not a specific protein that is involved in the transcription of. So that's why choice D is not correct. So again, the opera that encodes genes responsible for self regulation and production of proteins associated with light production or luminescence Is choice be the lux opera. See you in the next video
Related Practice
Textbook Question

The light-producing genes of V. fischeri are organized in an operon that is under positive control by an activator protein called LuxR. Would you expect the genes of this operon to be transcribed when LuxR is bound or not bound to a DNA regulatory sequence? Explain.

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Textbook Question

The diagram shown here is a model of the gene regulatory circuit for light production by V. fischeri cells. The lux operon contains genes for luminescence (luxCDABE) and a gene, luxI, that encodes an enzyme that catalyzes the production of an inducer. This inducer easily moves back and forth across the plasma membrane and acts as a signaling molecule. The lux operon is never completely turned off. The luxR gene codes for the activator LuxR. The inducer can bind to LuxR, and when it does, the LuxR–inducer complex can bind to a regulatory site to activate transcription of the lux operon and inhibit transcription of luxR. Explain how this gene regulatory circuit accounts for bacteria emitting light only when they reach a high cell density.

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Textbook Question

LuxR is allosterically regulated by the inducer molecule secreted by V. fischeri. What does it mean that LuxR is allosterically regulated?

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Textbook Question

Quorum sensing (introduced in Ch. 11, Section 11.4) allows bacteria to detect the number of neighboring cells and to trigger a response only when this number reaches a critical level. Quorum sensing is used by V. fischeri in light production and by many pathogenic bacteria, including Vibrio cholerae, to turn on genes for toxin production only when a critical cell density is reached. Why might quorum sensing be beneficial to pathogenic bacteria?

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