Dude, you need some medication or something. You seem to think the DNA was writ by the immortal hand of god and is therefore sacrosanct. It ain't. Mutation is natural. DNA is thermodynamically unstable. The mechanisms by which DNA is replicated induces errors. Each of us has a dozen or so mutations to our own DNA. Every organism is constantly undergoing mutation. It is possible, though very tedious, to simply use selective breeding and wait for nature to provide the qualities we seek, whether it is increased shelf-life or Roundup resistance. All that adding radiation or mutagenic chemicals does is speed up the clock to give us these desirable mutations, (along with thousands of useless mutations), faster. All that genetic engineering does is give us the exact changes we want more or less immediately.