Geneticin G-418 is an aminoglycoside antibiotic used for selection and maintenance of eukaryotic cells, including mammalian, yeast, plant, and protozoan cells, that express the aminoglycoside 3′-phosphotransferase (neo) resistance gene. It inhibits protein synthesis in susceptible cells, allowing enrichment of populations carrying plasmid or genomic integrations with the neo selectable marker.

The neo determinant provides selectable resistance in diverse systems and is genetically linked to kanamycin resistance in bacteria such as E. coli, enabling screening workflows that bridge prokaryotic cloning and eukaryotic expression. Geneticin G-418 can be incorporated into liquid or solid culture media for routine selection and maintenance of stable cell lines.