Is pleiotropy enhanced in transgenic organisms?
Critics will argue that pleiotropy has caused few if any problems with traditional breeding and should present no new problems for transgenic organisms. And, of course, sometimes a transgene will not even express at all, or only weakly, in a new host. Campbell (1990) has predicted that pleiotropy will not create major adaptive novelties in transgenic forms. Yet in fact both evidence and theory do suggest that pleiotropic effects are and should commonly, though not always, be greater in transgenic than in normal forms, even if pleiotropy is unlikely to create major adaptive novelties. The evidence that pleiotropic expression may often be unusually great in transgenic organisms suggests a need for at least some empirical observations to assure food safety, and to a lesser extent to assure ecological safety even for transgenic forms that one would idealistically suppose to be safe judging only from the primary effects of the transgenes and/or from teleological descriptions of the purposes
