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Suheir Sleiman
Substitution plan for IB Biology
Read individually the article below and then in pair answer the following questions:
Is the mitochondrial donation technique an ethical one or not? Support your answer clearly.
Add you answer to the Biology google drive (HW folder)
Article
An Overview of the Ethical Concerns Related to Three-parent Babies
People opt for in vitro fertilization for a variety of reasons such as infertility, miscarriages, and even the inheritance of
health disorders. In such cases, various technologies help in the conception of a viable and healthy offspring. The latest
technique to be developed is that of mitochondrial donation which results in a three-parent baby.
TAGGED UNDER: Human Genetics Designer Babies
Preventing a disease that can be passed down for generations would be ethical as long as it proves to be safe.
-Arthur Caplan
In recent times, a majority of the population leads a sedentary lifestyle. This, coupled with problems associated with
stress, food and water contamination, pollution, and addictive habits (smoking, drinking,etc), has led to the increased
prevalence of issues such as infertility and genetic health disorders. These issues have had a major impact on human
reproductive health. However, recent advancement in the field of medical sciences has led to the development of several
novel techniques and methodologies related to human reproduction and health. Collectively, they are known as assisted
reproductive technology (ART). It is used to achieve pregnancy or conception via procedures like artificial insemination,
fertility medications, in vitro fertilization, and surrogacy.
In vitro fertilization (IVF) is the most commonly used method to deal with infertility and concerns related to inheritable
diseases. IVF is used not only to establish successful pregnancies but also to screen the viable fetus for genetic disorders.
This screening is called pre-natal or pre-implantation genetic diagnosis. It involves studying the genome of the zygote and
establishing whether the offspring will develop any health disorder. In many cases, the parents often have a history of
some grave genetic disease, and wish to confirm its presence/absence in the fetus. This technology helps in selecting the
zygotes with the minimum chances of developing the disorder, and then implanting these zygotes in the uterus for the
progression of pregnancy. However, there are a few disorders that cannot be evaded by such means. These disorders are
health defects that arise due to the presence of faulty mitochondria. They are comparatively tough to resolve since genetic
disorders can be evaded to a certain extent by the random selection of one parent's healthy genes over the other parent's
mutated genes, but this is not so in the case of mitochondrial disorders as all progeny inherit only the mother's
mitochondrial DNA (in the process of fertilization, the father only contributes his genetic material).
Hence, if the mother's mitochondria are dysfunctional, her progeny will have dysfunctional mitochondria as well, which
would be exhibited in the form of myriad genetic and health disorders. To overcome this, a new technology has been
developed, which is called mitochondrial donation, and it results in a three-parent baby, i.e., the baby exhibits three
genetic parents.
Mitochondrial Donation
In cases where the mother possesses faulty mitochondrial DNA, a specialized form of IVF is utilized so as to introduce
mitochondrial DNA from a third party (another woman) into the zygote. Such a transfer of foreign mitochondrial DNA
ensures that the offspring does not suffer from mitochondrial disorders.
Since the mitochondrial DNA is introduced in the zygote, as and how the zygote develops, each cell of the offspring's
body will possess the same mitochondria, making it a germline modification. Future progeny of this offspring (if female),
will also possess healthy mitochondria. This also causes the offspring to possess three distinct genetic parents. The mother
and father provide the genetic material in the form of ovum and sperm, respectively, and the donor female provides the
mitochondrial DNA, in a process called three-parent in vitro fertilization (TPIVF). This technique helps in averting
diseases like diabetes mellitus, deafness, Leigh syndrome, etc.
Methods Involved
This process can be carried out in two ways: pronuclear transfer (PNT) and maternal spindle transfer (MST). According to
research studies involving primates and mice embryos, scientists claim that PNT may exhibit an increased risk for
inadvertent transfer of faulty mitochondria along with the genetic material, but MST shows an increased risk of
chromosomal abnormality. This indicates that both techniques have drawbacks of their own, and it is difficult to discern
which technique is better. Hence, in case of people opting for TPIVF, the technique to be used differs on a case to case
basis.
Pronuclear Transfer
◆ In this method, the maternal (patient) egg with abnormal mitochondria and the donor egg with the normal mitochondria
are both separately fertilized with the paternal (patient's partner) sperm. This leads to the formation of two zygotes with a
pronuclei in each (fused male and female genome). Then, the donor zygote is enucleated, i.e., the pronucleus is removed
and distracted. At the same time, the pronucleus from the patient's zygote is removed and is introduced into the donor
zygote with the normal mitochondria. This zygote is then allowed to progress and develop as an embryo, and is
transferred to the maternal uterus after cleavage of the zygote is initiated.
Maternal Spindle Transfer
◆ In this method, the spindle and associated chromosomes are removed in the form of a karyoplast from both the
maternal (patient) egg with abnormal mitochondria and the donor egg with the normal mitochondria. The karyoplast of
the donor is discarded, and that of the patient is introduced into the enucleated donor egg. Once the reintroduction of
karyoplast is successful, the egg is fertilized via administering an intra cytoplasmic sperm injection (ICSI) using the
paternal (patient's partner) sperm. Once the egg is fertilized and the zygote initiates the stages of cleavage, it can be
transferred to the maternal uterus, where it develops into a healthy fetus.