germline editing

Germline editing means changing the DNA of eggs, sperm, or very early embryos — the cells that pass life on. Because every cell of the resulting person grows from that starting point, the change is woven into all of them, including their own eggs or sperm. So unlike editing a patient's blood or liver, a germline edit does not stop with one person: it is inherited by their children, and their children's children, indefinitely.

Mechanically it uses the same editing tools, such as CRISPR, but applied at the very beginning of development rather than to a fully grown body. That timing is exactly what makes it heritable: edit the single founding cell, and every later cell copies the edit. There is no way to confine the change to one tissue or to take it back from future generations once those people exist.

This permanence is why germline editing is banned or heavily restricted for clinical use almost everywhere. The risks of an unintended change, the impossibility of consent from people not yet born, and the danger of treating human heredity as something to redesign make it one of the most serious ethical lines in all of biology.