If Hitler hadn't killed 11 million people, most people alive today wouldn't be. Returning to the original point. The question about pre-natal gene testing does

If Hitler hadn't killed 11 million people, most people alive today wouldn't be. Returning to the original point. The question about pre-natal gene testing does not seem to be about actually doing it routinely. Suppose that we devised a genetic test that can determine if a fertilized egg will grow into a gay adult if brought to maturity. If such a test works, it would mean that ones genes carries sufficient information to deterimine if one is gay. Wheater or not we actually use this on a given person does not change the fact that their genes are still sufficient.