The lac operon is an example of what type of operon?

Study for the DNA Structure, Replication, Transcription and Translation Test with flashcards and multiple choice questions. Each question offers hints and explanations. Prepare thoroughly and excel in your exam!

Multiple Choice

The lac operon is an example of what type of operon?

Explanation:
Inducible operons are turned on in response to a signal that relieves repression. For the lac operon, transcription is off when lactose is absent because the Lac repressor binds the operator and blocks RNA polymerase. When lactose is present, some of it is converted to allolactose, which binds the repressor and prevents it from sticking to the operator. With the repressor displaced, RNA polymerase can transcribe the operon, producing the enzymes needed to import and metabolize lactose. This on-demand expression in response to lactose is the hallmark of an inducible operon. It’s not constitutively on, and it’s not a repressible operon (which would be turned off by the product of a biosynthetic pathway). Glucose can further modulate expression through CAP-cAMP, reducing transcription when glucose is abundant, but the primary concept is that lactose induces expression.

Inducible operons are turned on in response to a signal that relieves repression. For the lac operon, transcription is off when lactose is absent because the Lac repressor binds the operator and blocks RNA polymerase. When lactose is present, some of it is converted to allolactose, which binds the repressor and prevents it from sticking to the operator. With the repressor displaced, RNA polymerase can transcribe the operon, producing the enzymes needed to import and metabolize lactose. This on-demand expression in response to lactose is the hallmark of an inducible operon. It’s not constitutively on, and it’s not a repressible operon (which would be turned off by the product of a biosynthetic pathway). Glucose can further modulate expression through CAP-cAMP, reducing transcription when glucose is abundant, but the primary concept is that lactose induces expression.

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