The lac operon in *E. coli* is a well studied inducible operon in *E. coli*. The lac operon genes code for proteins needed to break down lactose. When lactose is not present, the lac repressor binds to the lac operator sequence and prevents transcription. When lactose is present in the cell, it is converted to allolactose which is recognized by the lac repressor. Allolactose binds to the lac repressor and prevents it from binding the DNA. This allows transcription of genes needed to break down lactose in the cell. This processes allows for the cell to only encode genes needed for lactose break down when in the presence of lactose.

lac operon: gene regulation via lactose

Inducible operons typically encode proteins that use or break down specific molecules in the cell. Their expression is induced when in the presence of that molecule so that the operon is only expressed when the genes are needed to break down that compound.

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Operons are a section of genes that are all transcribed together. The operon is regulated by the promoter and operator sequence upstream of the genes in the operon. Operons are found primarily in prokaryotes.

Operon

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Repressible operons typically code for proteins needed to make products required for cellular pathways. When the cell requires the product of this operon, this operon will be expressed. But once the product is accumulated in the cell, it binds the repressor of the operon and the operon is repressed or turned off. This regulates the amount of products in the cell through gene regulation and expression. 

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