LacZα gene

 The LacZα gene is one of the structural genes present on the Lac Operon in Escherichia coli bacteria. When transcribed by RNA polymerase, the LacZα gene codes for β-galactosidase, an enzyme responsible for the hydrolysis of β-galactosides (e.g. lactose). On the lac operon, the LacZα gene exists between the operator region and the LacY gene.

The LacZα gene is only transcribed in certain conditions. Lactose must be present when glucose is unavailable due to the presence of a repressor protein (Lac repressor) on the operator region of the Lac Operon. This repressor protein prevents RNA polymerase from binding to the operator region; hence transcription of the structural genes cannot take place.

Fragments of the LacZα gene are also used in the recombinant DNA technologies to identify recombinant plasmids (a plasmid with a new section of DNA added) in bacterial colonies. New genes are inserted into the multiple cloning site (MCS), which lies in a region of the LacZα gene fragment. Therefore, recombinant bacteria produce β-galactosidase (as the LacZα gene is not disrupted), whereas the non-recombinant bacteria do not (as the LacZα gene is disrupted, therefore inactive). Hence, due to the LacZα gene, recombinant bacteria can be easily detected.