Question

What does the Lac operon of E.coli consist of? How is the operator switch turned on and off in the expression of genes in this operon? Explain

Answer 1

The lac operon consists of series of three genes in bacteria that produce the necessary enzymes to metabolise lactose and it also contains promotar and terminator regions. The three genes are lacZ, lacY and lacA. LacY produces an enzyme for transporting lactose through the cell membrane. LacZ enzyme required to separate lactose into galactose and glucose. LacA produces a molecule which metabolize galactose. There are two mechanisms to regulate the expression of lac operon. First, when lactose is not available to the organism, the organism cannot express the lac operon. This condition is caused by another gene lacl, which is present near the lac operon in the genome. It produces a protein which blocks the promoter region of the lac operon. This protein will bind to the operator region of the lac operon until molecules of lactose bind to it. When lactose is present in high concentrations, all of the lacl protein becomes unbound and the lac operon can be expressed. The second regulatory mechanism of the lac operon is the presence of glucose concentration. When glucose is absent, the expression of the lac operon is increased.