Last week the Latvian media sources discussed the news about the baby with the three genetic parents. Europe took this challenge in early 2015, after a law allowing the use of biological material fr om three people in the process of fertilisation was passed in the UK. The topic of "a child from three parents" attracts the attention of many specialists, but most experts still don't have a clear understanding of this issue, therefore Alexander Krivoharchenko, embryologist of "Mama Rīga" Reproductive Health Clinic with 33 years experience in embryology, author of more than 100 scientific publications and reviewer of publications in several international journals of medicine, will explain this matter to us.
Speaking only about the three genetic parents means misunderstanding the essence of the method. Indeed, the genetic material from three different people is used during the fertilisation, so the embryo combines information of three germ cells. At the same time, the child inherits the features of only two persons. To understand how this happens, you need to take into in-depth consideration the theory and methodology.
Every person has a mother and a father. The baby inherits half of its genetic material from the mother, and the other half from the father. This means that we receive one chromosome from the father and the other from the mother. Chromosomes contain DNA, and DNA contains coded information about all proteins found in our body. Proteins are responsible for the external manifestation of all functions and features. For example, specific proteins determine eye colour, nose shape and body proportions. This way the parents transfer their inheritance to their children.
DNA (deoxyribonucleic acid) is a specific biochemical compound that contains information. Thanks to egg and sperm DNA, we inherit a certain set of genes from our parents. Nuclear DNA (DNA in the cell nucleus) contains information about the inherited features. But DNA is contained not only in the cell nucleus. The cytoplasm of the human cell has mitochondria, which contain mitochondrial DNA.
In the words of a biology textbook, mitochondria are the "cell power stations". The main function of the mitochondria is the processing of biological energy. Through chemical reactions, mitochondria turn energy of the nutrients received by the cell into the universal energy molecule (ATP – adenosine triphosphate). Essentially, this energy is required for all biochemical processes. The transformation occurs during breathing cycle. As a result of oxidation reactions of various nutrients, the multi-purpose "life energy" is released. Mitochondria can also be considered a cell service station responsible for the cell "breathing".
Mitochondria are very conservative — all people on the planet have identical mitochondria. The shape of the person's ear or nose depends on the parents, but the mitochondria in the cells are universal. We can say that the mitochondrion is the living organism inside another organism. Mitochondrion also has its own personal DNA molecule. The molecule has a single spiral and a circular shape, and its structure is similar to the DNA of bacteria and contains only 37 genes. The DNA of mitochondria contains only "technical information" about the process of cell respiration. All people have the same mitochondrial DNA. But sometimes the mitochondrion DNA mutates, leading to disruption of the system.
The child receives mitochondria from his mother. Mitochondrion is located in the area of the spermatozoon's tail and ensures the mobility of sperm. When the spermatozoon enters the egg, its tail disappears and remains outside of the egg along with the mitochondrion. This means that all mitochondria in human body are received from the mother. And if the mother has mitochondrial diseases, they will be passed to the child. Violations of the mitochondrial DNA can lead to many complications, ranging from poor vision and chronic fatigue to extremely serious violations of muscle functions.
The UK legislation allowing in vitro fertilisation using donor mitochondria is applicable in cases wh ere the woman has the mitochondrial DNA mutations. Now these women have the opportunity to give birth to children without diseases caused by mutations of mitochondria.
The method is as follows: the nucleus of the mother's egg is transferred into the donor's egg with a healthy mitochondrion. This means that all of the genetic material that provides relationship of the baby and mother is fully preserved. The child does not inherit other people's features. The baby will receive a mechanism responsible for the cell respiration and energy accumulation process from a healthy donor. Using analogies, this method can be compared to organ transplantation. Basically, in vitro fertilisation using donor mitochondria is transplantation on the cell level.
This procedure is already known for a long time; it was first described by studies from the University of Newcastle (United Kingdom). But previously, legal restrictions were in effect prohibiting the use of this method in reproductive medicine. In the UK, the new law allows the official use of donor mitochondria in IVF (in vitro fertilisation - fertilisation in the laboratory). But, it should be noted that mitochondrial diseases are rare.
It is also worth mentioning that scientists call this method a new era in the field of artificial fertilisation.
Chief physician, obstetrician-gynecologist, fertility specialist, ESHRE member
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