. Regulation of gene expression We have previously established how DNA is organized into genes, how genes store genetic information, and how this information XII Std Zoology Chapter XII Std Zoology Chapter Molecular Genetics to the promotor site and transcribe the operon to produce lac mRNA which enables formation of all the required enzymes needed for lactose metabolism ( Fig. . ).
This regulation of lac operon by the repressor is an example of negative control of transcription initiation. Lac operon is also under the control of positive regulation as well.