Genetically engineered tomatoes. Conceptual computer illustration of a tomato (Lycopersicon esculentum) being injected with a syringe. Genetic engineering involves altering the DNA (deoxyribonucleic acid, double helices, silver) of an organism. This inherited substance controls the development and functioning of living organisms. A beneficial trait, such as resistance to a particular pesticide, can be introduced to a plant to increase its productivity.