Genetically engineered tomatoes. Conceptual image representing the farming of giant genetically engineered tomatoes. People in chemical suits are spraying the tomatoes, possibly with pesticide. The genetic engineering of plants involves altering their DNA (deoxyribonucleic acid), the chemical which controls an organism's growth and development. Traits such as resistance to diseases and pesticides can be introduced to the plant, which may save time and money during cultivation and harvesting.