GM food. Conceptual image of the genetic modification of food, showing the DNA base letters written in Alphabetti Spaghetti. DNA contains four different bases: adenine, thymine, cytosine and guanine, represented by their initial letter. Sequences of these bases form genes, which contain the instructions for making proteins. Inserting new genes into the genome of an organism can give it desirable properties, such as resistance to frost or delayed spoilage. Both pasta and bread are made from wheat, one of the most commonly genetically modified crops.