Lac operon is made up of one regulatory gene and three structural genes (z, y, a). Its function in the presence and the absence of inducer is as under: (i) When inducer (lactose) is absent i-gene regulates and produces repressor mRNA in the absence of lactose, which translate repressor. The repressor protein binds to the operator region of operon and as a result prevents RNA polymerase to bind to the operon. The operon is switched off in this situation. (ii) When inducer (lactose) is the present Lactose acts as an inducer and binds to the repressor. Thus, forming an inactive repressor.
The repressor fails to bind the operator region. The RNA polymerase binds to the operator and transcripts lac mRNA Lac mRNA is known to be polycistronic which produces all three enzymes, i.e. p-galactosidase, permease and trans acetylase. Operon is switched on in this situation.
Describe how the lac operon operates, both in the presence and the absence of an inducer in coli.
Answers
Rahul Jat
Lac operon is made up of one regulatory gene and three structural genes (z, y, a).
Its function in the presence and the absence of inducer is as under:
(i) When inducer (lactose) is absent i-gene regulates and produces repressor mRNA in the absence of lactose, which translate repressor. The repressor protein binds to the operator region of operon and as a result prevents RNA polymerase to bind to the operon. The operon is switched off in this situation. (ii) When inducer (lactose) is the present Lactose acts as an inducer and binds to the repressor. Thus, forming an inactive repressor.
The repressor fails to bind the operator region. The RNA polymerase binds to the operator and transcripts lac mRNA Lac mRNA is known to be polycistronic which produces all three enzymes, i.e. p-galactosidase, permease and trans acetylase. Operon is switched on in this situation.