Q&A: DNA breakthrough of world's first baby born with three genetic parents brings hope — and uncertainty

John Zhang holding the world's first three-parent baby. Pic: New Hope Fertility Center

Is it the birth of a new era for preventing genetic disorders or a case of scientists meddling too far, asks Caroline O’Doherty

What’s this latest breakthrough all about?

It’s being dubbed the ‘three-parent baby’ case as it uses genetic material, DNA, from three people to produce an embryo.

Why would you do that?

Because the DNA from one parent is defective and is likely to pass on a disease or disability to their baby, so if you can remove and replace it, the baby should be born healthy.

What’s the background to the current case?

Mom carried the genetic defect that causes Leigh syndrome, a mitochondrial condition from which her two daughters died. The mitochondria is the power pack in cells that enables them convert food into energy for growth and maintenance. It carries a relatively small number of genes, compared to the nucleus of the cell which carries the majority, but when it doesn’t work properly, cells can’t thrive or repair themselves and they malfunction and die, typically causing a whole range of neurological conditions.

What did doctors do?

They took a donor egg and removed its nucleus, replacing it with the nucleus of the mom’s egg, then fertilised that egg with her husband’s sperm and implanted the embryo that resulted. She later had a baby boy, born free of Leigh syndrome.

So will this only work where mitochondrial conditions are involved?

So far, that seems to be the case. Research is at a very early stage, however.

How early exactly?

The UK is the only country to have licenced the technique and even there it’s still being fine-tuned so it’s not available yet. The doctors who carried out the procedure reported this week are based in New York but treatment took place in Mexico because there are no laws there to breach.

But if it’s successful, why is it controversial?

Because even though the mitochondria carries only a tiny proportion of the genetic material that goes into making a human, it still means this baby has DNA from three people. That hasn’t been done before. The baby is five months old, too young to know if there will be long-term effects.

Does that mean fertility clinics here are unlikely to offer it any time soon?

It does.

But when it becomes the norm in other countries, presumably we’ll be ready to offer it here too?

There’s no guarantee. If it’s still of limited application, the number of parents it would help here would be very small. Also, our fertility clinics operate without legislative guidance so they are cautious about adopting new techniques.

Q. No laws? Is this Mexico?

A. No, this is Ireland where the Government can promise to legislate 11 years ago and then say two weeks ago that they’ll produce a general outline of proposed law next year, followed by a public consultation period, followed by more specific draft laws, followed by... you get the picture.

Have parents with suspected genetic conditions in their family line any other options to ensure they have healthy babies?

Two clinics here offer IVF that comes with preimplantation genetic screening so that embryos can be tested for genetic disorders before being implanted. But that means A, having IVF; and B, deciding to reject an embryo that tests positive. No easy choices there.

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