A few months ago, the first healthy child toever have DNA from three parents was born in New York to a couple from Jordan. This was due to mitochondrial replacement therapy, a controversial procedure in which nuclear DNA is removed from a donor egg cell containing healthy mitochondria, while the nuclear DNA from a potential mother with defective mitochondria is inserted into the donor cell. The donor egg cell with the mother’s nuclear DNA is then fertilized by the father’s sperm. Though this procedure is controversial because it utilizes DNA from three parents rather than two, it is necessary in the case where the mother’s mitochondria contains harmful DNA. This harmful mitochondrial DNA can be fatal to babies. The mother of the child recently born has ¼ of her mitochondria mutated, and had two children before this experiment that were both killed from Leigh Syndrome, caused by the defective mitochondria.
However, that does not mean that the experiment is 100% perfect. Often, a few of the defective mitochondria may alsobe taken out of the mother’s cell along with the nuclear DNA during a processcalled carry-over. This unhealthy mitochondria can become prevalent in the donor cell, and can outcompete the healthy mitochondria, replicating and becoming numerous enough to cause the disease in the child. Scientists believe that this is due to the speed of mitochondrial replication, as certain genes could cause some mitochondria to replicate faster than others, resulting in unhealthy mitochondria with these genes to become more prevalent than healthy mitochondria without. Scientists hope to combat this by matching mitochondrial haplotypes between the mother and donor cells so that their speed of replication would be about the same.
Though this experiment is revolutionary, the United States as well as many other countries ban the procedure. Because of this, the doctor who performed the procedure, Dr. Zhang, had to travel to Mexico along with the couple to complete the procedure legally. However, the UK may be the first country to explicitly allow this procedure, and if approved procedures may happen as early as March or April. This is extremely important because if a highly developed country allows a procedure with a high success rate, other countries may follow suit and allow couples where the mother has faulty mitochondria to have children of their own.