Read the following and answer the question given below:The lac operon...
Promoter helps in starting the process of transcription and provides a binding site to RNA polymerase.
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Read the following and answer the question given below:The lac operon...
The Promoter Provides a Binding Site to RNA Polymerase
The lac operon is a group of genes in bacteria that are responsible for the metabolism of lactose. It consists of a regulatory gene and three structural genes. The regulatory gene codes for a protein called the repressor, while the structural genes code for enzymes involved in lactose metabolism.
The binding of RNA polymerase to the promoter region of the operon is essential for the initiation of transcription. The promoter is a DNA sequence located upstream of the structural genes, and it serves as a recognition site for RNA polymerase. It provides a binding site for the enzyme to attach and begin the process of transcription.
Inducer Inactivation of the Repressor
The lac operon is subject to regulation by a protein called the repressor. In the absence of lactose, the repressor protein binds to a specific DNA sequence called the operator, which is located between the promoter and the structural genes. This binding prevents RNA polymerase from accessing the promoter, leading to the inhibition of transcription.
However, when lactose is present as an inducer, it binds to the repressor protein and causes a conformational change in its structure. This change in shape prevents the repressor from binding to the operator. As a result, RNA polymerase is no longer blocked and can bind to the promoter, initiating transcription.
The Role of Exons and Inducer
Exons are regions of DNA that are transcribed into mRNA and eventually translated into proteins. They are not directly involved in providing a binding site for RNA polymerase. Therefore, option 'A' (Exons) is not the correct answer.
The inducer, in this case, lactose, is responsible for inactivating the repressor protein. It is not directly involved in providing a binding site for RNA polymerase. Thus, option 'C' (Inducer) is also not the correct answer.
The Correct Answer: The Promoter
The correct answer is option 'B' (Promoter). The promoter region is located upstream of the structural genes and provides a binding site for RNA polymerase. It plays a crucial role in initiating transcription by facilitating the attachment of RNA polymerase to the DNA template.
By binding to the promoter, RNA polymerase can initiate the transcription process, leading to the synthesis of mRNA from the DNA template. This mRNA can then be translated into proteins, including the enzymes involved in lactose metabolism.
In summary, the lac operon is regulated by the repressor protein, which binds to the operator region and prevents RNA polymerase from transcribing the operon. The presence of lactose as an inducer inactivates the repressor, allowing RNA polymerase access to the promoter and initiating transcription. The promoter provides a binding site for RNA polymerase, enabling the transcription process to begin.
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