Genetically modified crops have quickly gone from farmer's best friend to profit killer. European countries have imposed strict limits on imports, and in the United States opponents are demanding better labeling. Yet tracking genetically modified foods through the distribution chain is difficult and expensive. To make it easier, Motorola's Clinical Micro Sensors unit and GeneScan Europe of Freiburg, Germany, have developed a portable gene detector. The prototype combines Motorola's eSensor DNA detection technology with GeneScan's collection of DNA probes. Users place a prepared sample in a matchbook-sized biochip cartridge that detects specific genes. The cartridge is then plugged into a toaster-sized reader controlled by a laptop computer. Motorola expects to ship the detector by year's end, and hopes to shrink the unit to a handheld device within three years.