Genes can travel to nearby, related plants on their own. This is called gene flow. The goal was to improve the nutritional value of soybeans by forcing them to produce more methionine, an essential amino acid. The gene from the Brazil nut was successfully transferred to soybeans. After this had been accomplished, but before the soybeans were sold commercially, independent researchers tested the soybeans to see if it would cause allergic reactions in people.
Many people are allergic to nuts, particularly Brazil nuts.
In some people, allergic reaction to Brazil nuts is swift and fatal. A series of laboratory tests on humans confirmed that the genetically modified soybeans did provoke Brazil-nut allergy in humans. They could not feed the genetically modified soybeans to people for fear of killing them, but through scratch tests on skin, they confirmed unequivocally that people allergic to Brazil nuts were allergic to the modified soybeans. Only tests on humans will suffice. Many genes are being taken now from bacteria and other life-forms whose allergenicity is entirely unknown, so federal regulations require no allergy testing in these cases.