Posted on March 18, 2015 at 12:03 AM
The story about the UK passing a law to allowa reproductive technology called mitochondrial donation, what has been informally known as three person or three parent embryos, recently dominated the news.Part of the reason this story received so much attention is because the idea of a child with more than two biological parents sounds really scary, even Frankensteinish.While new medical technologies often raise ethical concerns, it is imperative to understand the science behind these technologies in order to accurately assess the likelihood and degree of potential harms caused by these technologies. In the case of three parent embryos, once we understand the science, this technology is not as threatening as it may initially appear.
The UK will only allow mitochondrial donations in cases where women could pass along mitochondrial diseases to their children. There are various types of mitochondrial diseases, which affect approximately one in 8,500 people and can lead to serious and fatal conditions. The mitochondria are located in the cytoplasm of the cell and serve as the cell powerhouses. Mitochondria have their own set of DNA with the 37 genes and a mitochondrial disease occurs when there is a mutation in the mitochondrial DNA. Mitochondrial donation allows women who are at risk for passing along mitochondrial diseases to the children to avoid doing so by using the mitochondria of a donor. There are two ways this can be done. In the first way, known asmaternal spindle transfer technique, the nucleus from the donor egg is removed and replaced with the nucleus from the intended mother’s egg. The resultant eggwill carry the nucleus with all the genetic information from the intended mother, but will also contain the healthy mitochondrial DNA from the donor egg.The second way, known as pronuclear transfer, removes the nucleus from a donor embryo and replaces it with the nucleus of an embryo that contains the genetic material from intended mother and father. Here again,the resultant embryo contains the genetic material from the intended parents, but avoids inheriting mitochondrial diseases because donor mitochondria is used.
Children born from mitochondrial donation technically have three parents: the genetic material from the nucleus of the intended mother, the genetic material from the mitochondria of the egg or embryo donor, and genetic material from the father. However, there are only 37 genes in the mitochondria while there are around 20,000 genes in the nucleus. Furthermore, mitochondrial DNA does not code for physical or personality traits, traits we generallyassociate with what makes us who we are.Since the mitochondria are responsible for generating energy for the cell and not for our identity shaping characteristics, the mitochondrial donor isn’t a genetic parent in the same wayor to the same degree that the intended mother (i.e. the nucleus donor) is.
Part of the concern about a child having more than two genetic parents is that it will need to “designer babies.” For example, in the movie “Twins“, the scientists use of genetic materialof multiple men in order to create a “perfect” child, Arnold Schwarzenegger’s character. Mitochondrial donation is not an example of a designer babies because the goal of this technology is therapeutic, that is, to prevent a woman from passing on devastating genetic diseases to her child. Designer babies, in contrast, are usually created based on value preferences and for the sake of enhancement (e.g. wanting a tall, athletic, and intelligent child) rather than for medical indications.
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