Genetically engineered maize. Conceptual computer illustration of a strand of DNA on a genetically modified (GM) corn cob. DNA (deoxyribonucleic acid) is the molecule which controls the growth and development of all living things. It is made up of two sugar-phosphate strands (white) linked by pairs of four bases (spheres) along their lengths. Corn, or maize (Zea mays), is a crop grown throughout the warmer regions of the world. Genetic engineering involves altering an organism's DNA to give it beneficial traits. In crops, these may increase resistance to pests and diseases, give an increased yield and protect the plants from weedkillers.