Answer:
An operon consists of a group of genes which are controlled by a single promoter.
The lac operon present in the E.coli comprises of genes for making proteins which breakdown lactose into glucose.
Normally, the lac operon will be turned of by a repressor when there is not enough lactose present.
When lactose is present in the cell, the operon is activated when lacl forms a bond with the promoter region due to its changes in the structure. This causes the process of transcription to occur.