I learned that the human body is incredibly complex and that even the slightest change in a person's DNA can cause major effects to their body. It can also have a major effect on how the look. If I ever needed a reminder about that all I have to do is look at my children.
These boys are a mash-up of my wife and I. My wife is Hispanic and I am Caucasian – Scotch Irish to be more specific – and our children have traits of both. One has all the Hispanic features in his face, but has my pale Irish skin.
My other son is the spitting image of my side of the family, but has the temperament of my wife. (Don't tell her I said that.) All this was pre-programmed into them the second they were created. How much more miraculous and mysterious can you get. There is a lot of talk about designer babies and using genetics to make sure children have certain physical and emotional traits,
I my opinion that takes all the fun out of it. While I agree that if you can keep a child from having a debilitating disease or physical malformation, then genetically engineer away, but I would rather let chance and whatever creative force is out there in the universe decide if my son has blue eyes or brown.