...engineering is a tradition built on minimizing variation, while biology is a science founded on understanding a built-in mechanism for generating variation. "Life finds a way"....evolution is always driving against the engineered design
An engineer can design a system that creates 1000 screws with minimal variation. He understands all the effects of the different steel chemical makeups, he understands how to change the pitch and length to his specifications; he understands how to achieve each and every property of that screw, and once created, the screw will not act against its makeup.
A "genetic engineer" is presented with a million million variables. In altering a variable, he may observe some change – maybe some bioluminescence in fungus, some hairlessness in a mouse. But how much also changed that he cannot possibly observe? What other variables were dependent on the altered variable? As it is life, ever in flux, how much more will it change, itself, and its environment?
"Genetic engineering" should rather be called "unprecedented biological experimentation". This is important because "engineering" implies certainty, replicability. Altering some gene isn't engineering. It isn't minimizing variation in a system – it is introducing even more variation into that system. "Genetic engineering" certainly sounds cool and promising. But before you buy into a startup that employs "genetic engineering", don't be so certain; biology is much harder, much more complex, than screws.
[1] Or: Biology is really hard... | https://news.ycombinator.com/item?id=21396311