Kanamycin works by affecting the 30S ribosomal subunit and causing a frameshift mutation or it prevents the translation of RNA. This means that instead of a codon CAT (for example in sequence CATG), a codon ATG is read by aminoacyl tRNA (aa-tRNA). Aminoacyl tRNA is consequently carrying a different amino acid, because the anticodon on the aa-tRNA is different. The protein needed cannot be synthesized: depending on the site and severity of the frame shift, either a completely different protein is synthesized, or a protein similar to the one needed is synthesized, but is folded incorrectly. A bacterium is destroyed because it cannot produce any of its proteins correctly.citation needed
Kanamycin is not given to humans often because of its fairly toxic side-effects.
Genes encoding kanamycin resistance are commonly used as selectable markers in molecular biology.citation needed At least one such gene, Atwbc19[3] is native to a plant species, of comparatively large size and its coded protein acts in a manner which decreases the possibility of Horizontal Gene Transfer from the plant to bacteria; it may be incapable of giving resistance to kanamycin to bacteria even if gene transfer occurs.