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 development and growth of all living things. It is made up of two strands linked by a sequence of bases. Autoradiograms are a way of studying DNA which show the positions of DNA's bases as black bands. 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.