This summer, government health officials in the United Kingdom made headlines by announcing that they will let scientists create babies with DNA from three different people. The procedure is a type of in vitro fertilization (IVF) that would allow women with mitochondrial diseases to have healthy babies. If approved by British Parliament, the method, known as mitochondrial replacement, would lead to a historic event: the first genetically modified humans who could pass down those genetic tweaks to their children.

Some bioethicists and media commentators have voiced concerns about the technique's safety because so far it's only been tested on human cells in the laboratory.