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This week, scientists announced that a baby was born with three genetic parents.

No, this isn't some bizarre love triangle situation. The now five-month-old boy has DNA from his mother and father, plus a teeny bit from a donor. The baby's mother carried the genes for a fatal nervous system disorder called Leigh syndrome, but scientists were able to keep the disease from being passed on to her son by swapping in a donor's mitochondrial DNA, the tiny bit of DNA where this particular disease is housed.


Mitochondrial DNA is made up of just 37 genes and can only be passed on to a child by its mother. Replace that tiny bit of code through in vitro fertilization, though, and you can save a child from a deadly disorder they will otherwise definitely inherit.

This approach, dubbed the '3-parent' technique, is extremely controversial. So far, it has only been legally approved in the U.K. In the U.S., lawmakers have blocked the technology. The Jordanian parents of this new miracle of science had to travel to Mexico where the procedure was performed by U.S. doctors. In Mexico, said John Zhang, the scientist who led the effort, "there are no rules."


One reason the 3-parent technique is controversial is safety. In the 1990s several babies were actually born with genetic material from three 'parents' using a different technique, but some of them developed genetic disorders and the technology was never approved. Some critics also object to experimenting on what they view as a potential human life.

Perhaps the biggest fears, though, stem not from the technology itself, but what it might lead to. It raises questions of how much we're willing to tinker with the genetic makeup of our offspring—a question that becomes ever-more relevant as technology makes the once hypothetical entirely plausible.

"The proposed technology will interfere with and change the germ-line forever," Michael Nazir-Ali, a former U.K. bishop, wrote in The Telegraph last year. "This is breaking an international consensus that genetic engineering should not be used to modify human eggs or sperm in such a way as to alter the characteristics of future children."


When the U.K. gave the green light to the 3-parent technique earlier this year, the independent watchdog Human Genetics Alert claimed it was “the first step in a well mapped-out process leading to [genetically modified] babies, and a future of consumer eugenics.”

Mitochondrial diseases aren't the only disorders scientists are working to engineer out of human embryos.


In China, scientists have begun tweaking human embryos using the gene-editing technique CRISPR to try to make them HIV-resistant and modify the gene associated with a blood disorder.

CRISPR, a highly efficient gene-editing technology, has made fears of superhuman genetic mutants seem all the more prescient. With more accuracy than ever before, scientists can use CRISPR to snip out a little bit of problematic DNA or even add to an embryo something extra. Other scientists have proposed using it to correct the DNA of people carrying the deadly, breast-cancer causing BRCA1 gene or combining CRISPR with stem cell technology to create an even more powerful method of germ-line engineering.


CRISPR-engineered cows, pigs and other animals have already been born with enhanced resistance to disease or minus unnecessary traits, like horns on cows.

But before you start flipping out about designer babies, know that the reality is that this technology is still in its infancy. In the latest experiment in China, last April, 26 human embryos were targeted for modification and only four were successfully modified. A significant number of the other embryos showed signs of unintended mutations—CRISPR is more accurate than ever, but it is still not perfect enough to guarantee you won't accidentally snip a teeny bit of the wrong thing.


All of the embryos in the Chinese experiment were destroyed after three days. This technology is still a very long way off from allowing us to just cut and paste our way to the baby of our dreams.

The scientists behind the 3-parent baby found that less than 1% of the baby boy’s mitochondria carry the problematic mutation. The hope is that this number is low enough that he does not suffer any genetic problems. Both time and more births, though, will be necessary to judge how safe the technique really is. Scientists selected a male embryo on purpose, to ensure that if he does wind up with problematic mitochondrial mutations he cannot pass them on to his offspring.


These unknowns are why the National Institutes of Health has made it clear that it "will not fund any use of gene-editing technologies in human embryos" and why British regulatory authorities only approved gene editing in human embryos under the conditions of very strict regulatory oversight.

The abilities that science will perhaps give us to cure disease will certainly present complicated ethical dilemmas. But we're not quite living in that Brave New World yet.

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