Contrast positive versus negative control of gene expression.

Key Concepts

Gene Expression Control

Gene expression control refers to the mechanisms that regulate the transcription and translation of genes into proteins. This regulation is crucial for cellular function, allowing cells to respond to environmental changes and maintain homeostasis. It can occur at various stages, including transcription initiation, RNA processing, and translation.

Positive Control

Positive control of gene expression involves the activation of transcription by regulatory proteins called activators. These proteins bind to specific DNA sequences, enhancing the recruitment of RNA polymerase to the promoter region, thereby increasing the likelihood of gene transcription. An example is the lac operon in E. coli, where the presence of lactose activates gene expression.

Negative Control

Negative control of gene expression occurs when regulatory proteins, known as repressors, inhibit transcription. Repressors bind to operator regions on the DNA, blocking RNA polymerase from accessing the promoter and preventing gene expression. This mechanism allows cells to conserve resources by turning off genes when their products are not needed, as seen in the trp operon of E. coli.