Regulation of Gene Expression

Regulation of gene expression is the process by which gene activity is controlled, and its product is synthesised; gene expression ultimately results in the formation of a polypeptide.

Gene regulation can also be described as switching genes ON or OFF according to the cell's requirements and developmental stage.

• Genes in a cell are expressed to perform a particular function or a set of functions.
• Gene expression is regulated by metabolic, physiological, or environmental conditions.
• Coordinated regulation of multiple gene sets is responsible for development and differentiation from the embryo to the adult organism.

Levels of regulation in eukaryotes:

1. Transcriptional level: formation of the primary transcript.
2. Processing level: regulation of splicing.
3. Transport level: movement of mRNA from nucleus to cytoplasm.
4. Translational level: control at the stage of protein synthesis.
5. Additional control points include DNA rearrangements, RNA processing, mRNA stability, and translational control.

• Gene regulation = switching genes ON or OFF based on the cell's requirement and stage of development.
• In eukaryotes, regulation occurs at 4 levels: Transcriptional (primary transcript), Processing (splicing), Transport (mRNA from nucleus to cytoplasm), and Translational.
• In prokaryotes, control of transcriptional initiation rate is the main site for gene expression control.
• E. coli produces β-galactosidase to break lactose → galactose + glucose. If lactose is absent, the enzyme is not produced, proving the environment regulates gene expression.
• Enzymes synthesized based on substrate availability are called inducible enzymes. The process = induction; the triggering molecule = inducer. This is a positive control.
• Feedback repression = when the end product (e.g., amino acid) is already available, genes for its production are switched OFF. This is a negative control.