Animal Biotechnology

STABLE AND TRANSIENT TRANSFECTION

• For most applications of transfection, it is sufficient if the transfected genetic material is only temporarily expressed. Since the DNA introduced in the transfection process is usually not integrated into the nuclear genome, the foreign DNA will be diluted through mitosis or degraded.
• If it is desired that the transfected gene actually remains in the genome of the cell and its daughter cells, a stable transfection must occur. To accomplish this, a marker gene is co-transfected, which gives the cell some selectable advantage, such as resistance towards a certain toxin. Some (very few) of the transfected cells will, by chance, have integrated the foreign genetic material into their genome. If the toxin is then added to the cell culture, only those few cells with the marker gene integrated into their genomes will be able to proliferate, while other cells will die. After applying this selective stress (selection pressure) for some time, only the cells with a stable transfection remain and can be cultivated further.
• A common agent for stable transfection is Geneticin, also known as G418, which is a toxin that can be neutralized by the product of the neomycin resistant gene.