A common agent for selecting stable transfection is Geneticin, also known as G418, which is a toxin that can be neutralized by the product of the neomycin resistance gene.
Če se potem v celično kulturo doda toksin, bodo proliferacije zmožne le tiste celice, ki bodo imele v svoj genom vgrajen markerski gen. Ostale celice ne bodo preživele.