We discuss three specific ways in which genetic engineering differs from conventional breeding, and some of the implications for safety, in more detail. The argument is frequently made that genetic engineering is not only an extension of conventional breeding, but is more precise, and therefore safer. We believe that in fact it represents a quantum leap from conventional breeding, is more precise in one way, but more unpredictable in others. We discuss the following key areas of difference and their implications for unexpected effects: scope of genetic material transferred/unnatural recombination, location of the genetic insertions, and use of vectors designed to move and express genes across species barriers.