Transgenic organisms, such as strawberries with a fish gene inserted to improve frost resistance, could not possibly have occurred through natural reproduction. In nature, genetic material is not exchanged across boundaries that separate different species. Nature also places limits on the speed with which genetic change can take place within species. Genetic engineering ignores all such natural boundaries. Nuclear engineering is the only previous venture in science that is even remotely similar in nature to genetic engineering.
Nuclear energy is created by tinkering with the atom, a fundamental building block of matter.
Genetic engineers are tinkering with genes, the fundamental building blocks of life. A primary difference between nuclear fallout and genetic fallout is that living things reproduce and spread on their own. There is no way to put the genetic genie back in the bottle. We also have a right to question the economics of biotechnology, because the same corporations that brought us agricultural pesticides are now bringing us biotechnology. These firms introduced commercial pesticides fifty years ago without knowing the risks, because they were dealing with complex living organisms and couldn't possibly have known the risk.