This typically works by disrupting or removing the lethal gene during the cloning process, and unsuccessful clones where the lethal gene still remains intact would kill the host cells, therefore only successful clones are selected.
Este funciona normalmente distorsionando ou eliminando o xene letal durante o proceso de clonación, e os clons insatisfactorios, nos que o xene letal aínda permanece intacto matarían as células hóspede, polo que só se seleccionan os clons satisfactorios.