Last year, John Zhang, a New York endocrinologist who specializes in fertility, generated controversy when he announced that he helped a couple in Mexico have the first baby conceived with the genetic material of three different adults.
Many scientists were concerned that not enough research had been done to ensure that the procedure would be safe and that the baby would grow up healthy. But regardless of pushback, this baby's existence as well as the UK giving the official go-ahead for doctors to perform a similar procedure has raised a question: how is this even possible?
First of all, mitochondria replacement is only necessary if the partner who carries eggs has a mitochondrial disorder, which can lead to diseases such as Leigh syndrome in children. The mitochondria a child has are provided solely by the egg, since the mitochondria from the sperm are destroyed during fertilization.
Mitochondria have their own DNA and are considered the powerhouse of any cell — including the egg.
If a person has faulty mitochondria, then, they would need to have them replaced in order to have a healthy baby. The mitochondria that are used in this procedure come from a third person, one who also carries eggs.
The whole procedure goes like this:
Step 1. An egg that has faulty mitochondria is fertilized with sperm inside a culture dish.
Step 2. The nucleus of that fertilized egg is removed.
Step 3. The nucleus is then placed into a donor egg that has already had its nuclear material removed.
The end result is an egg that has the DNA material of the sperm and original egg as well as the DNA from the healthy mitochondria of the donor's egg.
Sorry, did we just blow your mind?
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