Answer:
The lac Z gene present in the bacteria is the main component of the lac operon. This gene codes for the enzyme known as β-galactosidase. This gene helps in the breakdown of the galactoside.
This gene is important to determine the transformant cells from the non transformant cells in the genetic engineering. The substrate used is X gal and IPTG. The non transformed cells has the functionally active β-galactosidase gene and results in the formation of blue colonies. The non transformed cells has non functional β-galactosidase gene that do not reduce the substrate and result in the formation of white colonies.