I don't know whether to be excited or terrified by the thought that we could soon have the ability to genetically modify our children's genome. This could be accomplished by tweaking the genes in young embryos or later on by "patching" the genome.
As pointed out by Radiolab, testing for genetic defects is already available and being performed and parents can opt to terminate pregnancy. (This article is not about live vs choice so moving on.) This does not mean we are genetically engineering our children, but moral arguments are essentially the same. And the result is the same in that we are causing a bit of selection to occur.
Taken to an extreme it would be possible to eliminate certain diseases from the human population. And what if testing were available to detect someone who was below average intelligence? Or poor athletic ability? Or unattractive? Is it okay to terminate pregnancy then? What bothers me more is that all of this costs money. Poor people can't choose what babies they have. But the wealthy can.
We live in a world where the wealthy have advantages of wealth, social status, education and stress free upbringing. This is not so for the poor, although it is still possible to raise yourself out of poverty and achieve the same level of comfort and dignity the wealthy do. But what if we lived in a world where the wealthy not only had the advantages of wealth, social status and education but also had access to genetic conditioning to become beautiful, strong and intelligent?
That would, over a matter of a couple generations create a gap between the rich and poor that COULD NOT BE SURMOUNTED.
A super race of elite people. Everything we've worked to accomplish: equality, opportunity, human rights, abolishment of class would disappear and be replaced by a class system where the elite truly were superior. Like modern day Pharaohs these genetic elites would control the world and pass it on to others like them while the poor and "inferior" languish and are likely to be subjects or slaves.