Genetically modified food. Conceptual computer artwork of a tangle of DNA (deoxyribonucleic acid) on a fork. This represents genetic modification of food crops. Two vertical strands of DNA (at lower left) show the structure of this macromolecule. It is a double helix held together be cross-linking strands called nucleotide bases. The sequence of these bases is the genetic code that determines inherited characteristics. Genetic modification is where an organism's DNA is altered to create inherited changes in that organism. The changes can include improved shelf-life and resistance to disease. DNA naturally exists in a tightly coiled state within cell nuclei.