IPTG (isopropylthio-β-galactoside) is an inducer of β-galactosidase activity in bacteria and is suitable for use with X-gal or bluo-gal to detect lac gene activity in cloning procedures.

How it works
IPTG binds to the lac repressor and releases lac repressor from the lac operator, thereby allowing the transcription of genes in the lac operon, such as the gene coding for β-galactosidase.