One in 6,000 babies affected by mitochondrial disorders are in jeopardy of experiencing slow and progressive deaths. A groundbreaking genetic technology known as 3-DNA has initiated both hope and controversy in the field of genetic medicine. However, they have the potential to be treated through 3-DNA technology, a process that involves manipulating human embryos and replacing defective mitochondrial DNA with healthy DNA from a third party.

Essentially, this process is like a DNA transplant and would help women who carry genetic disorders have healthy children. The process involves correcting faulty mitochondrial function without altering other traits like appearance or constituting the creation of a third parent. Despite its functional success, 3-DNA has fueled debate over ethical concerns, social consequences, and the unknown risks of crossing the germ line.

A typical human cell can have as many as 1,000 to 2,500 mitochondria depending on the cell’s function. Within the mitochondria are 37 genes, known as mitochondrial DNA, and even though they are simpler than nuclear genes, they still impact health if mutations or defects occur. However, unlike nuclear DNA, which is inherited from both parents, mitochondrial DNA is only passed down from the mother. A 3-DNA transplant involves addressing this maternal mitochondria.

Through advanced in-vitro fertilization (IVF) techniques, scientists can replace faulty mitochondrial DNA, leading to embryos free from mitochondrial disorders, while preserving the genetic identity of the parents. The mitochondrial replacement can occur before or after fertilization.

One process involves recruiting women with healthy mitochondrial DNA to donate eggs, fertilizing the egg to create an early embryo, and then removing DNA from the nucleus, leaving behind only healthy mitochondrial DNA. From there, nuclear DNA is added from the affected couple’s early embryo.

The second application of this method involves intervention before fertilization. The mother's nuclear material is saved in the unhealthy mitochondria, then the nucleus from the healthy mitochondria is removed and the donor egg is destroyed. The healthy egg can now be fertilized and the mother’s nuclear material is placed inside. The results of either method lead to a healthy embryo with healthy mitochondrial DNA of the donor and nuclear DNA of the mother and father.

Significant concerns about potential long-term implications and social consequences have raised ethical considerations surrounding 3-person DNA technology. Once changed, the DNA is permanently altered and then passed down to future generations. Any baby of a child born this way would have genes from three different people. This is known as germ-line genetic modification . While the germ-line modifications would be passed to every generation proceeding, it is important to note that people inherit mitochondrial DNA from their mothers, so only female children would pass their altered genetic code on.

Given that crossing the germ line has not been done before, the outcome is uncertain and could have unforeseen consequences for future generations. Additionally, some fear that this technology could deepen social inequalities if it becomes accessible to only the wealthy. This would lead to a genetic divide, or worse: designer babies and consumer eugenics where individuals select traits like appearance, intelligence, or athletic ability, further exacerbating societal disparities.

David King , a molecular biologist who runs a British genetic watchdog group says that using 3-DNA technology in this way could be “socially disastrous for our society.” Balancing the promise of eliminating genetic diseases with the risks of misuse and inequality remains a critical challenge for policymakers and scientists.