Unlike selective breeding, GMO takes genes from one species and inserts them into a different species. Selective breeding occurs within a single species, or several very closely related species. It is not fish genes in strawberries or tomatoes. GMO takes species that cannot cross breed, and "breeds" them with viable offspring. Most cross species breeding generally results in sterile offspring. Because only a few genes are changed, the reproductive system in GMO crops is not compromised. Much different than selective breeding.