Scientists create GE foods when they insert specific genes from one organism into the DNA of another organism. When this happens, a novel protein is created and the host organism will exhibit a new trait. For example, a gene which causes cold resistance in fish can be inserted into a tomato to make it withstand freezing. The danger in creating crops this way is that the novel proteins may act unpredictably.
Gene insertion is amazingly imprecise.
They are engineered to tolerate pesticides without being damaged. They are engineered to contain a pesticide within their cells. For example, rBGH is a growth hormone injected into cows to increase their milk production. Some animals are genetically engineered for a specific tarit. For example, chickens on some factory farms are engineered to have much larger breasts or thighs than normal.