G418 is an aminoglycoside antibiotic, which blocks polypeptide synthesis by interfering with the function of 80S ribosome. Due to its toxicity on prokaryotic and eukaryotic cells (including bacteria, fungi, plants and mammalian cells), it is widely used as a selective reagent for stable cell line construction. The resistance mechanism is based on that resistance gene (Neomycin) specifically express aminoglycoside phosphotransferase, which confers resistance on cells. Thus cells are able to grow in selective culture medium containing G418.