Q. Which of the following is required as inducer for the expression of Lac operon?
(a) Glucose
(b) Galactose
(c) Lactose
(d) Lactose and galactose
Solution :
Correct option : B 1.The lac z, lac y and lac a genes in lac operon are the structural genes that code for beta-galactosidase which converts lactose into glucose and galactose. 2.In lac operon, Lactose acts as an inducer for the synthesis of protein. 3.Lactose goes and binds with the repressor protein, causing an allosteric shift. 4.This altered repressor cannot bind to the operator, thereby making the promoter region accessible. 5.As the promoter region gets activated, the RNA polymerase enzyme initiates the transcription of the lac operon. 6.Thus, lactose is required for the expression of the lac operon.