Question
Explain the principles of positive and negative regulation of gene expression with reference to operons.
Answer :
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Gene expression in prokaryotes is primarily regulated at the level of transcription, and operons provide a classic model to understand positive and negative regulation. An operon is a cluster of structural genes under the control of a single promoter and operator, transcribed together as a polycistronic mRNA. Regulatory proteins interact with specific DNA sequences to either inhibit or stimulate transcription. Negative regulation occurs when a repressor protein binds to the operator region and prevents RNA polymerase from transcribing the structural genes. In the lac operon of Escherichia coli, the lac repressor binds to the operator in the absence of lactose,
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