Lac repressor

• e.coli can use lactose intseatd of glucose during respiration
• e.coli makes the enzyme b-galactosidase to digest lactose
• no lactose=no enzyme=gene isnt expressed
• the enzyme b-galactosidase is controlled by a transcription factor called the lac repressor
• When there is no lactose the lac repressor binds to the DNA at the start of the gene which created b-galactosidase to stop transcription