An  R  plasmid  consists  of a resistance transfer factor (RTF), which
   enables  conjugation, and one or more r-determinants: genes conferring
   resistance to antibiotics.

   The   r-determinants  in  this  diagram  are  Tc,  tetracycline;  Kan,
   kanamycin; Sm, streptomycin; Su, sulfonamide; Amp, ampicillin; and Hg,
   mercury.