Three is no longer a crowd, thanks to pioneering scientist John Zhang, who recently helped a Jordanian couple have a baby with a little genetic input from a third party. The procedure, which took place in Mexico where there are no laws banning Zhang’s method, resulted in the birth of a baby boy on April 6 this year.
The boy’s mother carries a genetic mutation for a deadly disease called Leigh syndrome, which prevents the nervous system from developing properly. Though she herself doesn’t actually suffer from the condition, the couple’s two previous children both died as a result of it.
The mutation responsible for this illness is contained within the mitochondrial DNA, which is only passed down the maternal line. This genetic material is made up of a small number of genes that aren’t the same as those found in nuclear DNA, which occurs in the nucleus of every cell in the body.
Zhang used a process called spindle nuclear transfer, which involved removing the nucleus from one of the mother’s eggs and inserting it into the egg of a donor, which had its own nucleus removed. The new egg therefore contained the mother’s nuclear DNA and the donor’s healthy mitochondrial DNA. It was then fertilized with the father’s sperm, before being placed into the mother’s womb and allowed to develop as normal.
Though the moral and ethical implications of this type of procedure are controversial, Zhang told New Scientist that he believes in what he is doing, saying “to save lives is the ethical thing to do.”
Analysis has shown only about 1 percent of the baby boy’s mitochondrial DNA carries the mutation for Leigh syndrome, which doctors hope is too small an amount to actually produce symptoms – although only time will tell if he really has avoided the deadly condition.
The fact that the baby is male is also an advantage in this case, as it means he won’t pass on this mitochondrial DNA to any children that he may have in the future. Therefore, as long as he himself doesn’t develop the illness, it can be guaranteed that Leigh syndrome has been completely eradicated from the family line.