Lac operon or lactose operon is the operon or a cluster of genes that have one promoter encoding genes for the metabolism and transport of lactose in bacteria.
It is found in E. coli and other bacteria.
It produces a lac repressor protein in the bacteria.
The y gene in lac operon codes for the enzyme permease which is involved in maintaining the lactose permeability in the cell, therefore, increasing the concentration of lactose in that cell.