The team used proteins that bind to DNA and RNA to control the manner in which certain genes were expressed in a mammalian cell. This yielded a transcription-translation "device," somewhat like a DNA transistor, that the team could rewire to complete different tasks. In one example, the gene network worked as an AND gate. Both the apple molecule and the antibiotic "inputs" need to be present in order for it to work. The gene network triggers the formation of a fluorescent protein, which serves as the "one." If both inputs are not present, the cell will not fluoresce.