Genetically engineered tomatoes. Overripe tomatoes (left) compared to genetically engineered or modified (GM) tomatoes (right). By altering the DNA (deoxyribonucleic acid) in the genes of the tomato, different properties can be introduced to the plant. These are Flavr Savr tomatoes, the first GM food to be sold (in 1994). The genetic engineering of this variety of tomato, allows it to avoid spoilage during storage & transportation for much longer periods than normal tomatoes.