Name the genes that constitute an operon. how does operon get switched on in the presence of lactose ?

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​Please find below the solution to the asked query        

Genes constituting lac operon:
 

Gene	Nature	Function
i gene	Inhibitor	It codes for repressor of lac operon.
z gene	Structural	It codes for β-galactosidase.
y gene	Structural	It codes for permease, which increases the permeability of cell to β-galactosidase.
a gene	Structural	It codes for transacetylase.

 All genes involved in lac operon are required for metabolism of lactose.  Lactose acts as an inducer for lac operon since it regulates the switching on and off of the operon.
Regulation in Presence of Inducer

• Inducer binds with the protein product of gene i (repressor) and inactivates it.
• This inactivated repressor is unable to inactivate RNA polymerase enzyme and z, y, and a genes synthesise their respective mRNA, which in turn gets translated to form β-galactosidase, permease, and transacetylase.
• In presence of all these enzymes, the metabolism of lactose proceeds in a normal manner.

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Hope this information will clear your doubts about the topic.    Regards