Each of the potatoes is regular in shape and has a pale brown skin that shines under the bright lights of the high-tech greenhouse. They look like ordinary spuds waiting their turn for a one, way trip to the chip pan or the cooker but, despite their mundane honey appearance, they're not. The potatoes, fresh from the greenhouse of Professor Charles Arntzen at Cornell University in New York, are part of a revolution that is turning bananas, corn, beans, tomatoes and may other corps into drugs, vaccines and antiobiotics. Scientists around the world are currently altering the genetic profile of these plants, so that they can grow proteins and antibodies that will fight off or prevent disease in the humans that eat them.