Unexpected Risks Found In Editing Genes To Prevent Inherited Disorders

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The genes in mitochondria, which are the powerhouses in human cells, can cause fatal inherited disease. But replacing the bad genes may cause other health problems.

In September, reproductive endocrinologist John Zhang and his team at the New Hope Fertility Center in New York City captured the world’s attention when they announced the birth of a child to a mother carrying a fatal genetic defect.

Using a technique called mitochondrial replacement therapy, the researchers combined DNA from two women and one man to bypass the defect and produce a healthy baby boy — one with, quite literally, three genetic parents.

It was heralded as a stunning technological leap for in vitro fertilization, albeit one that the team was forced to perform in Mexico, because the technique has not been approved in the United States.

The technique is spreading quickly, gaining official approval this month from the Human Fertilization and Embryology Authority in the U.K. The move will allow clinics to apply for permission there to carry out the treatment, with the first patients expected to be seen as early as next year.

But for all the accolades, the method also has scientists concerned that the fatally flawed mitochondria can resurface to threaten a child’s health.