"Three-parent" children: the discussion continues
Can a child have three parents
At this meeting, they will discuss whether or not to allow clinical trials of a new assisted reproductive technology that should help women with genetic defects in mitochondrial DNA.
Mitochondria in eukaryotic cells convert nutrients entering the cell into a universal energy currency – ATP molecules. Most likely, mitochondria were once free-living bacteria, but have entered into a mutually beneficial alliance with eukaryotic cells. Mitochondria, like bacteria, multiply by division. These bacteria had their own genome, and the remnants of it have survived to this day. In animals, the mitochondrial genome contains 37 genes. These are not all the genes that are needed for the construction and vital activity of the mitochondria, many genes have long migrated to the nucleus.
As in any other DNA, mutations can occur in the mitochondrial. Some of these mutations cause diseases. During fertilization, only the DNA contained in the nucleus gets into the egg from the sperm. Because of this, the next generation gets only the maternal mitochondria. There is no recombination with mitochondrial DNA, its molecules simply double and diverge into two new mitochondria randomly. Symptoms of the disease appear when there are too many abnormal chromosomes. Since there is no recombination, if the mutation is in the mother, it will definitely be in all her children, grandchildren, etc.
About 4,000 children a year are born with life-incompatible pathologies of mitochondrial origin. Another number of people live with diseases of very different symptoms and severity of the course. A new reproductive technology can help them all. In fact, it is a variant of in vitro fertilization, in which another step has been added. For this step, a donor egg is needed – a woman's egg that does not contain defective mitochondria. In such an egg, a nucleus is transplanted from the egg of a woman who wants to become a mother, but cannot because of mutations in mitochondrial DNA, or who has a high probability that the child will be seriously ill. This procedure is well developed thanks, for example, to developments in the field of cloning. After that, the egg is fertilized by the sperm of the future father and implanted, as with conventional IVF.
It turns out that a child who can be born during such a procedure will inherit genetic material from three different people and will actually have three parents.
What difficulties can arise here?
First of all, technical. They seem to have been overcome. The probability that after all these manipulations, the cell will divide and develop normally is actually equal to the probability for an ordinary egg, with which nothing was done. In 2009, during such a procedure, apparently healthy rhesus macaque cubs were born.
The first attempt to apply this technology to humans was made in 2001, but ended in failure. It remains unclear whether the failure was caused by an imperfection of technology or a genetic defect of the mother. Then the procedure was considered as a kind of gene therapy. The FDA considered the safety evidence insufficient, and research in this area was suspended.
Another problem is that it is proposed to mix the genetic material of different women, and they may be incompatible. A number of examples were given when such mixing for mice, fruit flies and other animals led to early death, decreased growth rate, premature aging and decreased fertility. Proponents of the method claim that in these experiments the genetic material of animals of different pure lines obtained by closely related crosses was mixed. Laboratory tests are carried out on them for greater accuracy and better reproducibility, but they cannot be called normal from a genetic point of view. In humans, it's the opposite: children from mixed marriages and their offspring are usually no worse adapted.
In addition to technical difficulties, there are also legal and ethical difficulties. After all, a child born as a result of such a procedure will, from some point of view, have three parents who have passed on their genes to him. The current point of view is as follows: egg donation in this case should be considered as donation of any organ or tissue. It should be anonymous: the future child should not be able to find out the name of the donor. Ethical complexities are beyond the FDA's field of view.
In the UK, regulators agree to allow clinical trials, subject to long-term follow-up of people who will be born as a result of the procedure. The relevant documents are being prepared now. The parliament will vote on this issue next year. It is necessary, since the British Parliament previously banned the modification of germ cells.
Portal "Eternal youth" http://vechnayamolodost.ru21.10.2013