Transgenic organism

A transgenic organism carries one or more genes, called transgenes, moved into it from another species in the laboratory rather than by breeding. It is one kind of genetically modified organism (GMO); that broader term also covers organisms whose own genes have been edited or switched off without any foreign DNA being added. If the transgene enters the germ line, offspring inherit it like any other gene.

Scientists insert transgenes in several ways. In plants, a common method uses the soil bacterium Agrobacterium tumefaciens, which naturally transfers part of its Ti plasmid into plant cells; researchers swap its tumor-causing genes for the gene they want. Transgenic mice are often made by injecting DNA into a newly fertilized egg or by modifying embryonic stem cells. Bacteria and yeast readily take up engineered plasmids and are used to make human proteins such as insulin.

They matter in research, farming and medicine. Mice carrying human disease genes serve as models for testing treatments, and reporter transgenes such as the jellyfish gene for green fluorescent protein show where and when genes are active. Crops given a gene from the bacterium Bacillus thuringiensis make their own insect-killing protein, and some goats and sheep secrete human proteins in their milk. Most countries regulate them for health and environmental safety.