[Myrddin]

The initial genetic configuration is only a start. Many changes will occur during development that alter the final result. Nutrition, maternal hormones, maternal disease and exposure to toxic substances will result in something different that what the initial configuration would "predict". Consider every Windows or Linux installation DVD as the starting material. The hardware and exposure to operating will change the running system over time. It is preposterous to claim that you can definitively claim the genetic markers you identify will be expressed in the end product.

[HiTech RedNeck]

Genes are, pardon the term, viral. They go to every cell. Nobody knows how to roll them back on a bodywide basis, like patching a Windows or Linux installation. The only real scientific issue is whether the sought marker shows up as a diseased phenotype in all cases or only some.