Antibiotic resistance genes are used in some GMOs to identify plants where the added DNA has been successfully incorporated. While this idea could understandably lead to questions -- Antibiotic resistance genes in my food? -- multiple safety reviews conducted by regulatory agencies around the world have confirmed that the presence of an antibiotic resistance gene does not pose any unique safety concerns.
One of the first steps associated with GMO development is identifying the plants that contain a functional copy of the transferred DNA. To produce a successful GMO crop plant, developers must start with dozens, hundreds or even thousands of plants. Antibiotic resistance genes allow GMO developers to conduct screening tests early in the development process to rapidly identify only the desired plants. Antibiotic resistance genes work by producing proteins that metabolize a specific type of antibiotic. Plants with the gene are identified by how they grow in the presence of the antibiotic. Antibiotic resistance genes are also referred to as marker genes.
Just like the proteins that allow GMOs to control insect pests, for example, the proteins produced by antibiotic resistance genes undergo an extensive testing process to ensure they are not allergenic or toxic. Numerous studies have also demonstrated that consuming these proteins does not interfere with antibiotic treatments, nor do the genes themselves transfer from plants to other organisms. These topics have been reviewed by FDA and the European Food Safety Authority.
If the new GMO being developed can be identified without the antibiotic resistance marker, such as a plant resistant to a herbicide, then it can be screened based on how it grows in the presence of the herbicide, and the additional marker is not required.
Techniques to remove marker genes have been used in GMO development. In one of the more recent methods, a DNA sequence containing two separate regions is inserted into the plant. One region contains the gene that provides insect protection, for example, and the other region contains the marker gene. Plants containing the entire DNA sequence can be easily identified, as described above. These plants are then crossed with another plant that does not contain any inserted DNA. The two regions of DNA segregate away from each other in the resulting offspring, and only those plants containing the gene of interest, with no marker gene, move on for further evaluation and testing.