Tet-on/Tet-off system

The Tet-off and Tet-on system is a popular tool for regulating genes. It utilizes tetracycline (Tc) or doxycycline (Dox, a Tc derivative) as the switch control. In the Tet-off system, the gene expression is turned off when Tc or Dox is present in the medium, whereas in the Tet-on system, the gene expression is turned on when Dox is present. The Tet-on system is responsive only to Dox, and not to Tc. In this case, expression of GOI is being controlled by the Tet-off system.

Figure 1: Diagram of the on and off states of the Tet system.

The gene encoding for tTA and the promoter followed by your gene of interest can be on separate plasmids.