How does genetic manipulation actually work

I know it can choose genders/looks/abilities, but HOW do they make it happen? How would they make a child have blonde hair, be very smart, be very athletically talented, etc?

This is very, very tricky. I have no problem with experimentation to try to cure genetically inherited and often fatal diseases such as cystic fibrosis, Huntington's disease, hemophilia, that sort of thing. I have grave concerns about trying to engineer human beings to have certain traits. Look in the history books about World War ll; creating a 'master race' is, in my opinion, taking this too far. Your children are your children; we all have different talents and weaknesses, we all have our unique phenotypes, and to try to manipulate that so that our children have blonde hair and blue eyes and are all little geniuses raises a very, very big red flag in my mind. We're nowhere near able to do that yet, but I think that any human genetic engineering should be to cure illnesses, not to try to make our offspring into the image of what we think is a perfect human being. Our differences are what make our species strong, and to tamper in the natural variation of genotypes and phenotypes just to produce certain superficial traits is treading in very dangerous waters.
This is just my humble opinion, but this sort of 'brave new world' genetic tinkering seems morally wrong to me.
Use genetic manipulation to eliminate fatal diseases, fine..but not to create cookie-cutter children!

Read about it here
http://library.thinkquest.org/20830/Mani…