nucleic acid transfection PSI-MI nucl transfection MI:0312 Introducing DNA into eukaryotic cells, such as animal cells, is called transfection. Transfection typically involves opening transient "holes" or gates in cells to allow the entry of extracellular molecules, typically supercoiled plasmid DNA, but also siRNA, among others. Transfection differs from transformation since the DNA is not generally incorporated into the cell's genome, it is only transiently expressed. nucleic acid delivery