Most importantly, the gene in this network of interactions, is not stable. There are a number of different mechanisms that are designed to destabilize the genes under certain conditions inside and outside the body. The DNA may mutate and new pieces may be inserted or pieces may be deleted or multiplied many times. Sequences of the genetic code may be rearranged or combined with other sequences. Some genes can jump around between different places in the chromosomes.
Some genes can convert other genes to their own DNA sequence.
These fluid genome processes are not at all haphazard, accidental or meaningless. They occur, under the control of the cell, as adaptive responses to various conditions. For example, plants exposed to herbicides or insects to insecticides are able to respond by mutations that make them resistant to the harmful influence. They responded directly to substances that they are normally unable to metabolize by mutating so that they became able to feed upon this new nutritional source. The mismatch between reality and the mindset of genetic engineering does not only make genetic engineering unpredictable, it may also be dangerous.