Controversy in Science

Debate Over DNA: Preimplantation Genetic Diagnosis

My previous posts have covered the discoveries of scientists and of myself, a hapless student discovering what scientific research is all about. I am now introducing Debate Over DNA, which is about misconception and controversy in genetics.

Preimplantation Genetic Diagnosis (PGD) is the ability to determine genetic conditions in a child that hasn’t been born yet. We can diagnose the embryo (when the egg from a female and the sperm from a male fuse) before it is implanted into the mother. Genetic screening and diagnosis allows parents to make better choices for their child’s future.

In Vitro Fertilisation (IVF) is required to create an embryo ex uterto (outside the body). IVF is one of the few available treatments for infertility and is useful for when there is a risk of a hereditary disease being passed on. The zygotes (the eggs and sperm) are collected and the sperm is manually injected into the egg to make an embryo. The embryos stay in culture for a few days and then one embryo is implanted into the mother’s uterus (her womb). The other embryos aren’t implanted to avoid having multiple children and are instead frozen for future applications.


A diagram showing the IVF process. Image from Wikimedia


On day three, a cell is taken from the IVF embryo to undergo PGD. This involves a genetic analysis of the DNA within the cell. The Polymerase Chain Reaction (PCR) is used to amplify the DNA, and then Fluorescence In Situ Hybridisation (FISH) allows the binding of fluorescent probes to the defective part of the DNA. An embryo without the defect present is then selected for implantation.


An embryo biopsy, which is when one of the cells from an 8-cell embryo is removed. Image from iStock


I believe that PGD is massively beneficial, as it effectively reduces the risk of inheriting a harmful genetic condition. The fact that this is all done in a petri dish, however, is a controversial topic. Do we have a right to intervene with what nature intended? In this post I have highlighted some of the debates and myths associated with PGD.


Nature In Utero vs. Nurture Ex Utero

The use of PGD is well-regulated and justified. There are nearly 400 conditions in the UK where PGD is legal, with the requirement that the condition affects their quality of life. PGD reduces the number of children born with a predisposed genetic condition. A diagnosis once the embryo has started developing gives parents a more difficult choice as to whether to terminate an affected fetus or not. In contrast, choosing to terminate an 8-cell embryo may not be as unethical as terminating a pregnancy because it is not as far along in development as a fetus would be. This means that the requirement for abortion is also reduced.

On the other hand, our ability to select which embryos develop could be interpreted as us ‘playing God’. To some, an embryo has the same right as a person to live, so the destruction of embryos that may or may not even have the defect can be viewed as wasting potential life. There is also the argument that individuals with existing genetic conditions may begin to feel socially-isolated as the number of those affected decreases. In the situation of a parent, however, it is easy to empathise and choose the option which gives a healthy child.


Saviour Siblings

PGD can be used for saviour siblings. For a child born with a genetic condition such as some cancers, their sibling may be able to provide an organ or cell transplant. The embryo for this saviour sibling is produced using IVF, and then PGD is used to ensure that;

a) They too don’t have the condition, and;

b) That their HLA genes (involved in the immune response) are compatible so that rejection after a transplant doesn’t occur.

Although this benefits the affected child, it is controversial as the sole purpose of that child is to make their sibling better. There is the question of whether informed consent should be required, but often these transplants occur at such a young age that parental consent is adequate, so the saviour sibling hasn’t had a say. If you enjoy a cup of tea and a good book like I do, then I recommend reading ‘My Sister’s Keeper’ by Jodie Picoult as it highlights the controversy surrounding saviour siblings.


Will this lead to Designer Babies?

With the potential to screen for many genetic defects, where should we draw the line? There is talk of Designer Babies, which is when desirable traits that do not significantly improve the child’s health are selected for. For example, embryos could be chosen without the genes dictating poor eyesight or premature balding.


Totally nailing this look, not the Designer Baby that I’m on about though… Image from Wikipedia


The Human Fertilisation and Embryology Authority (HFEA) regulates under what circumstances this interference can occur and the research that is carried out on embryos. In 2006, HFEA allowed genetic screening in embryos of genes that can lead to certain cancers in middle-age, and have given permission for ‘three-parent babies’ to be born later this year.

For now, ethical complications and tight regulations mean that the selection of desirable traits is highly unlikely, but as processes like this become easier to conduct, it does allow a future where we can select desirable traits. HFEA have prohibited the use of reproductive cloning, but this research is legal in other countries. Is it likely that HFEA will also follow suit to diminish undesirable characteristics?


I hope this post has cleared up any previous misconceptions that you had on PGD. Do you believe that that the application of PGD will become less restricted as time goes on?

6 thoughts on “Debate Over DNA: Preimplantation Genetic Diagnosis”

  1. Very interesting topic. Well written and informative post 😊 General public should know more about PGD and the low risk of creating ‘designer babies’ because so far(r) these are the sources of massive controversies online. Well done for explaining the principles:) I will definitely read the book you recommended 👌

    Liked by 2 people

    1. Thank you very much! 🙂 And definitely – once you realise that there is so much regulation behind all these procedures then there is little to worry about! Definitely, any book by Jodie Picoult in general is a winner!

      Liked by 2 people

  2. Great post going over the general ethical issues that PGD could cause! I personally hope that as our knowledge of diseases increase so will our ability to use PGD, to try and avoiding suffering. Especially now when it looks increasingly likely that we will be able to use base editing to stop diseases caused by simple base mutations. As long as there had been ethical consideration and there is legislation in place to ensure that it cannot be abused I’m all for it!

    Liked by 2 people

    1. I agree! It does seem like geneticists have a massive opportunity to help treat many genetic diseases, but you’re right when you say that a lot of thought has to go into the regulatory guidelines and the ethical implications of gene editing!

      Liked by 1 person

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