Tomatoes, Potatoes, Peppers, Corn, Soy, Watermelons, Strawberries, Peanuts and legumes, tree nuts, grains...almost any kind of vegetable, grain, or fruit food has a strain that has been modified, and that 'model' patented. Some have been modified to increase yield, some have been modified to change texture, some have been modified to remove seeds, some have been modified to make them sterile.
There could be fish DNA in your tomato.