create a short paragraph explaining The lactose (lac) operon in E. coli is an example of a gene that is repressed when lactose is not available in a cell. In 3-5 sentences, explain what this means, using correct terminology.
The lactose (lac) operon in E. coli is a cluster of genes involved in the metabolism of lactose. When lactose is not available in the cell, a repressor protein binds to the operator region of the operon, preventing transcription of the genes. The repressor protein is activated by the absence of lactose, specifically by its isomer allolactose. Once lactose becomes available, it binds to and inactivates the repressor protein, allowing RNA polymerase to bind to the promoter region and initiate transcription of the genes involved in lactose metabolism. This regulatory mechanism ensures that the cell only produces the necessary enzymes for lactose utilization when lactose is present.
