How does the lac repressor inhibit transcription?
Question
How does the lac repressor inhibit transcription?
Solution
The lac repressor inhibits transcription by binding to the operator region of the lac operon. Here are the steps involved:
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The lac operon is a group of genes involved in lactose metabolism in bacteria. It consists of three main components: the promoter, the operator, and the structural genes (lacZ, lacY, and lacA).
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In the absence of lactose, the lac repressor protein is active and binds to the operator region. This binding prevents RNA polymerase from binding to the promoter and initiating transcription.
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The lac repressor protein undergoes a conformational change when lactose is present. Lactose acts as an inducer by binding to the lac repressor and causing it to release from the operator.
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Once the lac repressor is no longer bound to the operator, RNA polymerase can bind to the promoter and initiate transcription of the structural genes.
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Transcription of the lacZ gene produces the enzyme β-galactosidase, which is responsible for breaking down lactose into glucose and galactose.
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Transcription of the lacY gene produces the lactose permease protein, which facilitates the uptake of lactose into the bacterial cell.
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Transcription of the lacA gene produces the transacetylase enzyme, which is involved in the metabolism of lactose by the bacteria.
In summary, the lac repressor inhibits transcription by binding to the operator region of the lac operon. This binding prevents RNA polymerase from initiating transcription. However, when lactose is present, it acts as an inducer and causes the lac repressor to release from the operator, allowing transcription to occur.
Similar Questions
How does the lac repressor inhibit transcription? Group of answer choices It binds to the RNA polymerase and prevents its association to the DNA.It binds to RNA polymerase and causes a frame shift, thus producing an mRNA with a nonsense mutation.It binds to the DNA and prevents the RNA polymerase from unwinding and transcribing the DNA.It binds to the mRNA molecule, preventing ribosomes from binding.None of the answers is correct.
The lac operon system, first described by Jacob and Monod, regulates lactose metabolism in . The is composed of a gene encoding a protein that normally keeps this operon in the position. Within the , the repressor binds to the , blocking transcription of structural genes needed for lactose metabolism. When is added to a cell's environment, it binds the repressor freeing the operator segment of the DNA. is now able to bind to the promoter, transcribing all three structural genes needed for lactose catabolism. When lactose again becomes depleted in the cell, the repressor binds to the operator blocking additional synthesis of enzymes from the .
Lactose or its analogues act as positive regulators of Lac operon by:Select one:a. Attaching to I gene and preventing its expressionb. Binding to repressor subunits so that the repressor cannot attached to operator locus.c. Increasing the synthesis of catabolic gene activator protein.d. Attaching to promoter region and facilitating the biding of RNA polymerase
When RNA polymerase is bound to the lac promoter sequence, transcription of the lac operon is on.
When both CAP and the lac repressor are bound as shown in the figure below, what happens to the genes in the lac operon?Group of answer choicesThe genes are transcribed once, but after that the repressor protein displaces the activatorThe genes are transcribed at a high level, because the activator will block the activity of the repressorThe genes are transcribed at a very low level, because when the repressor is bound to DNA it blocks RNA polymerase.The genes are transcribed half of the time, because the activator and repressor will each "win" half of the time
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