Tet-On 3G (also known as rtTA-V16[citation needed]) is similar to Tet-On Advanced but was derived from rtTA2S-S2 rather than rtTA2S-M2. It is also human codon optimized and composed of 3 minimal VP16 activation domains. However, the Tet-On 3G protein has 5 amino acid differences compared to Tet-On Advanced which appear to increase its sensitivity to Dox even further. Tet-On 3G is sensitive to 100-fold less Dox and is 7-fold more active than the original Tet-On