a) Binds to- dissociate from - operator - promoter. When the lactose is present it binds to the repressor and forms a confirmation change in it so that the repressor can no longer bind to the operator. And then RNA polymerase binds to the promoter region and allows transcription. Solution a) Binds to- dissociate from - operator - promoter. When the lactose is present it binds to the repressor and forms a confirmation change in it so that the repressor can no longer bind to the operator. And then RNA polymerase binds to the promoter region and allows transcription..