Old Blue Eyes

This genetic research thing has me very captivated of late. They've discovered with absolute certainty that when a person with blue eyes has a child with another person with blue eyes there is a 100 percent chance that the children will also have blue eyes. There is no chance of variation on this. Blue is the only eye colour that this happens with. If two people with brown eyes meet and have kids there is a possibility of the children having eyes with another colour. Green meets green can have kids with eyes of another colour. But with blue it is a genetic oddity that the offspring can only have blue eyes. This knowledge may have caused some very serious marital strain for previous generations.
I wonder what the Nazi regime in Germany would have thought of the recent breakthroughs in genetic manipulation humanity has accomplished. Or what they would have thought of our motivations for doing so.