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The UK just took a historic step toward allowing the creation of babies with three parents

  1. Members of Parliament in the UK's House of Commons passed regulations today that could allow the creation of babies from three people to prevent mitochondrial disease.
  2. If the regulations pass the House of Lords, the UK will be the first country in the world to have laws allowing this procedure.
  3. Mitochondrial disease is a serious genetic defect that can cause muscle wasting, brain damage, blindness, and in some cases, death.
  4. The regulations would allow doctors to use DNA from two parents plus a healthy donor's egg (without nuclear DNA) to create a healthy embryo, which would then be implanted into the mother's uterus.

Creating babies from three people could cure mitochondrial disease

These three-parent babies are an attempt to curb mitochondrial disease, which affects about one in every 6,500 babies. Infants with this disease have very little energy and muscle weakness. The disease can also lead to brain damage and blindness — and in severe cases, it can be fatal. Mitochondrial disease is genetic, passed down through the cellular material of a mother's egg. (Mitochondria, which have their own set of DNA, are called the powerhouses of cells because they create energy molecules that make cells work.) The idea is to replace those unhealthy mitochondria with ones from a healthy donor.

The babies would almost entirely be like the product of two parents

The technique uses a modified version of in-vitro fertilization, which combines a woman's egg and a man's sperm to make an embryo in a lab and then putting that into a woman's uterus. The three-person embryo could be developed in one of two ways.

Scientists could take the DNA of the mother and put it into the egg of a healthy donor woman — which includes healthy mitochondria — and then add the father's DNA. Or, they can create an embryo with the parents' DNA, take out the nucleus, and place that into an embryo from a healthy donor woman.

Here's one way the modification could work. The other method would repair the egg of a mother with diseased mitochondrial DNA. (Human Fertilisation and Embryo Authority)

The baby would, for all intents and purposes, seem to very much be the product of its two parents. Almost all of the DNA comes from them. But the babies would also have 0.1 percent of their total DNA from the healthy mitochondrial donor. That genetic change would permanently fix the mitochondrial disease both in the baby and in any future generations.

The process is controversial for ethical reasons

Catholic and Anglican Churches in England called the procedure unsafe and unethical because it could involve the destruction of embryos. (One method of creating a three-parent baby involves taking DNA from two embryos to help form a third, healthy one. The other embryo is destroyed in the process.)

During the 90 minute debate before the vote, Conservative member of Parliament Fiona Bruce argued, "This is about the principle of genetically altering, even genetically creating, a human being."

Other groups warned against the potential slippery slope of genetic modification, worried that it might one day allow embryos to be modified for looks or intelligence.

But Public Health Minister Jane Ellison countered that this is "a considered and informed step ... This is world-leading science within a highly respected regulatory regime," she said. "And for the many families affected, this is light at the end of a very dark tunnel."