Practice question

Kanamycin resistance in cloning vectors is generally mediated by kanamycin resistance determinant encoding aminoglycoside 3'-phosphotransferase type II, product of nptII or kanR gene derived from bacterial transposon Tn5. This enzyme phosphorylates kanamycin, inactivating its ability to bind 30S ribosomal subunit and cause mistranslation and bacterial cell death. Cells expressing the resistance grow on media containing kanamycin at 25-50 µg per mL for selection. Neomycin resistance similarly uses nptII, while AmpR encodes β-lactamase and TetR encodes tetracycline efflux pump with distinct antibiotic specificities unrelated to kanamycin.