A black and white photo of a toddler is featured, broken into block pieces, some mismatched, rearranged, and missing.

An advisory committee of the Food and Drug Administration is set to begin two days of meetings tomorrow to consider radical biological procedures that, if successful, would produce genetically modified human beings. This is a dangerous step. These techniques would change every cell in the bodies of children born as a result of their use, and these alterations would be passed down to future generations.

The F.D.A. calls them mitochondrial manipulation technologies. The procedures involve removing the nuclear material either from the egg or embryo of a woman with inheritable mitochondrial disease and inserting it into a healthy egg or embryo of a donor whose own nuclear material has been discarded. Any offspring would carry genetic material from three people — the nuclear DNA of the mother and father, and the mitochondrial DNA of the donor.

Roughly 1,000 to 4,000 children born in the United States each year will develop a mitochondrial disease, most by age 10, with symptoms that can range from mild to devastating. These diseases typically prevent mitochondria from converting food into energy and are the result...