Identify similarities and differences between an inducible operon and a repressible operon in terms of

the transcription-regulating DNA sequences.

Key Concepts

Operons

Operons are clusters of genes under the control of a single promoter, allowing coordinated regulation of gene expression in prokaryotes. They consist of structural genes, a promoter, and regulatory sequences. Understanding operons is crucial for analyzing how genes are turned on or off in response to environmental changes.

Inducible Operons

Inducible operons are typically off but can be activated in response to specific signals, such as the presence of a substrate. The classic example is the lac operon, which is activated when lactose is available, allowing the transcription of genes needed for lactose metabolism. This mechanism enables bacteria to adapt to changing nutrient conditions.

Repressible Operons

Repressible operons are usually active but can be inhibited by specific molecules, often end products of a metabolic pathway. A well-known example is the trp operon, which is repressed when tryptophan levels are high, preventing the synthesis of tryptophan when it is abundant. This feedback mechanism helps maintain homeostasis within the cell.