Mitochondrial Replacement Therapy: What Is Mitochondrial Donation And A 3-Parent Baby?

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Mitochondrial donation is a technique of in-vitro fertilization where healthy mitochondrial content is donated by a donor; the baby conceived in such a way is called a 3-parent baby.

What comes to mind you hear the word Mitochondria? The most obvious answer is that it’s the powerhouse of a living cell! However, did you also know that this simple organelle is responsible for causing a variety of life-threatening diseases in humans? That’s right! If the functioning of the mitochondria goes wrong, a person can suffer from stroke and even organ failure. The question is, can we donate mitochondria to other people? And if so, why might we need to? Let’s find out!

Mitochondria(CI Photos)s
Mitochondria under a microscope (Photo Credit : CI Photos/Shutterstock)

When an egg is combined with a sperm outside the body in controlled conditions, this process is called in vitro fertilization. Mitochondrial Donation is a method of in vitro fertilization when the mitochondrial content of the developing embryo comes from a third party. As such, if the mother carries the DNA that causes the mitochondrial disease, then they won’t be passed further, and a healthy baby could still be born.

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What Are Mitochondria, And How Can They Be Diseased?

Mitochondria are one of the cell organelles that are present in large numbers in mammalian cells’ cytoplasm. They undergo a process called oxidative phosphorylation, which produces molecules of Adenosine Triphosphate, better known as ATP. ATP is the energy currency of the cell, which is why the term ‘powerhouse of the cell’ is appropriate for mitochondria. One can easily conclude that if the energy requirements of an organ is greater, then the cells of that organ will have a greater number of mitochondria.

Structure of a mitochondrion (Photo Credit : Designua/Shutterstock)

However, another exciting thing about this organelle is that it has its own genetic material. We refer to this genetic material as Mitochondrial DNA, which is written as mtDNA. This mitochondrial DNA is “naked DNA” and as such, is very prone to mutations. Generally, when these mutations are minimal, few changes are observed, but as these mutations accumulate, severe disorders in the body can be seen. These are referred to as mitochondrial diseases.

One very crucial point to note is that the maternal oocyte transmits the mitochondrial content in an embryo during the fusion of the oocyte and sperm. This means that the offspring can inherit even harmful mutations.

Also Read: What Are Mitochondria?

What Is Mitochondrial Donation?

Mitochondrial donation is also known as Mitochondrial Manipulation Technology (MMT). It refers to the elimination of risk of mitochondrial diseases from the fertilized egg. In this technique, the mitochondrial content of the diseased mother’s egg is replaced with that from a healthy female’s egg. As such, the mitochondrial content of the future baby comes from a third party.

Maternal Spindle Transfer Technique

This procedure takes places via two standard techniques. The first technique is called the Maternal Spindle Transfer Technique, in which genetic materials from three different sources are mixed in vitro. The genetic material in every cell is present in its nucleus, while the mitochondria are only present in the cytoplasm. As such, the nucleus of the egg from the healthy female is removed, and then the nucleus from the biological mother is injected. The oocyte thus created is then fused with the sperm. Since the diseased cytoplasm is no longer present in the embryo, the future baby is born healthy!

Pronuclear Transfer

The other method is called the Pronuclear Transfer. Usually, when the sperm and the egg fuse, they result in the formation of pronuclei. A pronucleus is a membrane-bound structure that holds the nucleus from the sperm and the egg separately. Thus, two fusions are conducted in vitro: the fusion of the egg and sperm from the biological parents and the fusion of the egg of the donor with the sperm of the father. The pronuclei formed by the parents can now replace the donor pronuclei, which results in a healthy baby!

babies of three-parent(Designua)S
A diagrammatic representation of Pronuclear Transfer (Photo Credit : Designua/Shutterstock)

Also Read: What Is A Zygote? How Is It Different From An Embryo?

What Is A Three Parent Baby?

When a mitochondrial replacement therapy/technique is used to conceive a child, it is dubbed a ‘three-parent baby’. This corresponds to the fact that the baby contains genetic material from three sources. However, several scientists consider this term to be mere sensationalism. It is not a scientific term and was only dubbed by the press after the first such child was conceived in Mexico.

Artificial insemination, in vitro fertilization IVF of human egg cell or fertility treatment(Maxx-Studio)s
In vitro fertilization (Photo Credit : Maxx-Studio/Shutterstock)

There are a variety of different reasons why this term is not okay for a baby born through mitochondrial donation. To begin with, the donor transfers only 37 genes to the child, as compared to more than 20,000 genes transferred by the biological mother. Moreover, the donor has no role in bringing up the child, so calling a child a three-parent baby has the potential to be offensive, hurtful, or just inaccurate.


Mitochondrial Donation has proven itself to be a boon for diseases that were incurable in the past. It has become a fundamental technique related to in-vitro fertilization, as it can help couples with mitochondrial mutations conceive a disease-free baby. Many disorders, including Leigh Syndrome, finds its cure through the use of this technique. Even so, the research on these methods and other underlying factors is ongoing and dynamic, so while many babies have been born this way, there is still much more to learn!

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References (click to expand)
  1. Mitochondrial Replacement Therapy – UMDF -
  2. Mani, S., Saxena, N., Taneja, N., & Shome, P. (2018). Mitochondrial donation: A boon or curse for the treatment of incurable mitochondrial diseases. Journal of Human Reproductive Sciences. Medknow.
  3. How to make a 'three-parent' baby - Science News Explores.
  4. Mitochondrial Transfer: The making of three-parent babies. Harvard University
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About the Author

Bhoomika has a degree in Biological Sciences from Sophia Girls College, Ajmer. Apart from writing, she adores travelling to offbeat destinations that offer more than just tourism. Being a strong supporter of women in STEM, she derives her inspiration from trailblazing personalities such as Marie Curie and Jane Goodall.