Mitochondrial DNA is passed down exclusively from the mother. It is circular (as opposed to the linear DNA in the nucleus), and its genome contains 37 genes that code for the production of 13 proteins, 22 tRNAs, and 2 rRNAs. The mitochondrial genome also has a higher mutation rate when compared to the nuclear genome - about 100 times higher. 

While not every genetic mutation is bad, there are some mutations in mitochondrial DNA that can result in devastating diseases. If a mother has mitochondrial DNA containing mutations which cause harmful diseases, they will be passed on and could potentially cause illness in the child. In the past, some women have opted out of having children in order to prevent passing down those mutations. Now, scientists may have found a solution for those women looking to start a family.

Mitochondrial DNA is passed down via the egg. The DNA in the nucleus inside the egg is a combination between mother and father. To avoid using the mother’s egg which could pass down potentially deleterious mutations, a second female is required. The nucleus is removed from the donor egg and is replaced by the nuclear DNA of the mother. Sperm from the father is then injected into the egg, fertilizing it. The embryo can then be implanted into the mother with the mitochondrial mutations, and it will progress with a normal pregnancy and delivery.

Surprisingly enough, this concept isn’t new. Three-parent IVF has been performed on rhesus monkeys, who are alive and healthy four years later. Earlier this year, it was demonstrated that this technique is possible to do with human cells as well, though there have been some ethical concerns.

Last week, the FDA began to discuss the ethical, legal, and technical obstacles that will inherently come with human trials and clinical practice of this technique. Many speculate that it will gain approval.