Human genetic modification is the direct manipulation of the genome using molecular engineering techniques. Recently developed techniques for modifying genes are often called “gene editing.” Genetic modification can be applied in two very different ways: “somatic genetic modification” and “germline genetic modification.”
Somatic genetic modification adds, cuts, or changes the genes in some of the cells of an existing person, typically to alleviate a medical condition. These gene therapy techniques are approaching clinical practice, but only for a few conditions, and at a very high cost.
Germline genetic modification would change the genes in eggs, sperm, or early embryos. Often referred to as “inheritable genetic modification” or “gene editing for reproduction,” these alterations would appear in every cell of the person who developed from that gamete or embryo, and also in all subsequent generations. Germline modification has not been tried in humans, but it would be, by far, the most consequential type of genetic modification. If used for enhancement purposes, it could open the door to a new market-based form of eugenics. Human germline modification has been prohibited by law in more than 40 countries, and by a binding international treaty of the Council of Europe.