Regulation of Gene Expression All the genes are not activated constantly. The genes are needed only when proteins are needed. These are thus called regulatory genes and are made to function only when required and remain non-functional at other times. Such regulated genes, therefore, are required to be switched ‘on’or ‘off’ when a particular function is to begin or stop. These genes form an ‘operon’. Lac Operon
- An operon consists of structural genes, operator genes, promoter genes, regulator genes, and repressor.
- Lac operon consists of Lac Z, Lac Y, and Lac A genes as structural genes. These genes code for specific enzymes. Lac Z codes for galactosidase, Lac Y codes for permease and Lac A codes for transacetylase. When repressor molecules bind the operator, the transcription process is inhibited.
- When the repressor does not bind the operator and instead inducer binds, transcription is switched on. In the case of lac operon, lactose is an inducer. So, binding of the lactose to the repressor, switches on the transcription.
- In Transcription, with the help of RNA polymerase enzymes, the messenger RNA is produced. The main function of mRNA is to facilitate the synthesis of a protein.