Genetically engineered maize. Conceptual computer illustration of a DNA autoradiogram superimposed 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 strands linked by a sequence of base pairs along their length. The positions of the base pairs are represented by the dark bands on the autoradiogram. Corn, or maize (Zea mays), is a crop grown in the warmer parts of the world. Genetic engineering involves altering an organism's DNA to impart beneficial traits. In crops, these often increase resistance to diseases or protect the plants from weedkillers.