Antibiotic Resistance Gene

Gene conferring resistance to an antibiotic; used as a genetic marker

Various microorganisms have genes that make them resistant to antibiotics naturally produced by moulds. These genes are used by scientists to "mark" transformed plants and microorganisms. 

Many different genes are known that confer resistance to range of antibiotics. The nptII gene, which confers resistance to the antibiotic kanamycin, is often used in genetic engineering.