The United Kingdom is set to become the birthplace of the world's first three-person baby after British MPs voted in favour of changing genetic laws on Tuesday.
The House of Commons voted 382 to 128 in favour of an amendment to the 2008 Human Fertilisation and Embryology Act that would allow scientists to create babies by combining DNA from a mother, father and female donor.
The amendment will go before the House of Lords, and could become law in Britain by October.
While the goal of scientists is to allow women with incurable genetic disease to deliver healthy babies with the help of the female donor, critics say the prodecure will make it possible for doctors to play God and create designer babies.
According to Dr. Peter Lin, CBC Radio's medical columnist, three-person babies may mean the end of specific forms of genetic disease, but the procedure, which involves intervening in in vitro fertilization (IVF), poses risk and may raise questions about medical ethics in the future.
The female donor
The role of the female donor in creating three-person babies is to replace mitochondria, or what Dr. Lin calls "power stations" that exist in all cells of the human body.
Mitochondria are tasked with making energy for cells, and the blueprint for a baby's mitochondria comes solely from the mother.
If she has mitochondrial disease — which may result in physical, developmental and mental disabilities — the baby will have it, too.
Disease-related complications may set in even before the baby is born: Some women who are afflicted report not being able to reproduce at all.
"There was one patient who said she had eight miscarriages," Dr. Lin said.
By replacing the mother's damaged mitochondria with that of a healthy female donor, scientists are able to give healthy babies to women who carry the disease.
In this graphic created by CBC News, the DNA, or nucleus, of the mother's egg is put into the egg of the female donor, who has healthy mitochondria. This creates an egg with the mother's DNA that is free of mitochondrial disease. (CBC)
Hybrid cell
The IVF intervention involves taking a cell from a healthy female donor and replacing her DNA, found inside that cell, with the DNA of a fertilized egg.
"So take out the whole nucleus [of the healthy woman], so all you're left with is an empty cell with the proper mitochondria," Dr. Lin said.
"Then the couple will have their fertilized egg and you take that nucleus...and you pluck it into that empty cell."
The hybrid cell contains the couple's DNA and healthy mitochondria. That cell marks the beginning point for all other cells, and the end point for the female donor.
In this graphic created by CBC News, the DNA, or nucleus, of the embryo comes from the parents, while the cell and mitochondria come from the female donor. (CBC)
Traits
Physical, intellectual and emotional traits are derived only from the mother and father.
"All the important genes...your hair colour, how tall you are, all of that stuff is actually coming from the parents," Dr. Lin said.
He compared the relationship between female donor and baby to that of organ donor and recipient.
"It's kind of like if I donated a kidney to you. I'm not really part of you, right? I'm not your parent," he said. "That would be the same kind of concept."
Playing God, commercialized genetic surgery
According to Dr. Lin, the vote has critics questioning everything from its meaning for medical ethics to the procedure's long-term effects on the babies that come from it.
Those looking at it from a scientific perspective have asked about the interaction between nucleus DNA and donated mitochondria, and if there will be complications for the three-person baby as he or she grows into a child, and eventually an adult.
"So they're saying [scientists] don't know a lot of these things," Dr. Lin said.
Religious critics have questioned if scientists who perform the IVF intervention are playing God, or paving the way for the designer baby; one whose genetic composition is selected to meet a particular criteria.
While he acknowledges the new law will create a grey zone, Dr. Lin says the possibilities presented by combining DNA of three individuals makes the practice worth exploring.
"And I think it's going to head towards these other genetic diseases [like] Huntington's, where we can sort of do "genetic surgeries." Where we cut out the bad genes and put in good ones — that might be in the future," he said.
One question asked by critics and scientists alike: Where do you draw the line?
Using the gene for obesity as an example, Dr. Lin questioned what will happen if in the future, scientists decide to cut it out and replace it with the "skinny" gene.
"So now every single embryo would have to go through this process," he said.
Another potential issue? When genetic surgery becomes commercialized and profitable.
"So now you start having people say 'well yeah we can get rid of all the genetic stuff but we can also pick hair colour…. For a price.' That would be taking us down sort of the wrong path."
Scientists may find answers to these questions quickly.
If the amendment becomes a law by October as expected, the first three-person baby could be born in 2016.
What do you think?
Should laws in Canada change to allow three-person babies?
Dr. Peter Lin is the director of primary care initiatives at the Canadian Heart Research Centre and the associate editor of Elsevier WebPortal - PracticeUpdate Primary Care. You can hear him every Wednesday on Information Radio on CBC Radio One.
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