Reproductive Genetics

Adult self-modification is harder than embryonic intervention because adult bodies contain tens of trillions of cells. Embryo selection chooses among existing embryos, while genetic engineering corrects or changes genetic errors. Embryonic intervention is easier in principle because a change made at the one-cell stage can be inherited by later cells. Human enhancement is treated as more ethically difficult than disease correction. In vitro gametogenesis could make eggs or sperm in the laboratory and transform IVF by reducing the egg-supply bottleneck. If IVG makes many eggs cheaply, parents could create and screen many more embryos without gene editing.