Twin girls Lulu and Nana are the first two humans whose genomes have been altered in a laboratory - when they were embryos - and a third such baby is due to be born next month.
Loretta Magagula, a PhD candidate in medical biochemistry at UCT, spoke about the “designer babies” at the Pint of Science science festival in Cape Town last week.
“You’re actually designing humans,” she said. “You’re playing God.”
It’s not unrealistic to imagine a future in which you can select your baby’s eye colour or sporting ability when it is a single cell - but Magagula warns that genes are more complicated than many imagine.
“It’s easier when it’s a single trait you’re trying to edit,” she said. “Complex traits like eye colour and intelligence are more difficult (to manipulate) because they involve many genes working together.”
In October last year, Lulu and Nana - pseudonyms - were born in China.
A month later their birth sent shock waves through the international scientific community when Chinese biophysics researcher He Jiankui released a video on YouTube in which he said he edited their genes when they were embryos.
He said he used CRISPR technology to edit a single gene in both girls to make them unable to contract HIV.
He said following the editing their mother Grace’s pregnancy proceeded as normal. Jiankui says on his YouTube channel: “Grace started her pregnancy by regular IVF, with one difference.
“Right after we sent her husband’s sperm into her egg, we also sent in a little bit of protein and instruction for a gene surgery. When Lulu and Nana were just a single cell, this surgery removed the doorway through which HIV enters people.
“The girls are safe and healthy.”
Jiankui said he edited the girls’ genomes on the eve of the Second International Summit on Human Genome Editing, held in Hong Kong in November last year.
He was excoriated by scientists in the field, fired from the Southern University of Science and Technology in Shenzhen, and later detained by the Chinese government.
But Lulu and Nana were not the last of Jiankui’s experiments. Another gene-edited baby is in utero, and is due to be born next month - prompting calls from scientists around the world for countries to introduce legislation banning this type of experimentation.
CRISPR technology was introduced in laboratories around the world around five years ago, and has since become widely used in medical gene therapy and research into cures or treatments for diseases such as cancer.
So why has Jiankui’s work caused an outcry?
“The big debate is between somatic and germline cells. That’s where the line is drawn,” Magagula said.
Somatic cells make up nearly all of the body. If you edit genes from these cells and place them back in the body, as is being done in many experimental medical treatments, the edited genes cannot be passed on to progeny.
Germline cells are egg and sperm cells. If you edit genes from these cells, the changes are hereditary, effectively entering the human gene pool and changing it forever - which is what Jiankui did.
“When you start editing human embryos, you’re actually designing a whole different class of human,” Magagula said.
One of the dangers of such editing is that there is no way to predict the long-term consequences.
Another concern is that the person on whom such editing is performed will have to live with the outcome of a highly experimental procedure.
For Magagula, a huge concern is that if this process becomes commercialised, companies could create population groups with special traits - essentially a “super race” of humans.
“We’ll be renewing eugenics if we produce designer babies,” she warned.
“And you don’t just affect that person - Lulu and Nana will pass the edited trait on to their offspring.”
Another potential disaster lies in the accuracy of the CRISPR process.
“Trust me, we do it in the lab all the time. We can never predict where else in the genome CRISPR may cut and we may not even be able to identify it.”