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It is not certain that it is possible to choose whether the child born through in vitro fertilization will be taller or smarter

A new study led by Dr. Shai Karmi from the Hebrew University published in Cell magazine, lowers expectations for the next generation "improvement" through genetic testing of embryos

Selection of genetic traits. Illustration: shutterstock
Selection of genetic traits. Illustration: shutterstock

Carrier parents of disease-causing mutations are at high risk of giving birth to children with severe genetic diseases. Genetic testing of embryos (Preimplantation genetic diagnosis, or PGD) is an old technology that helps carrier couples to give birth to healthy children. In this technology, the parents undergo in vitro fertilization (IVF) in order to create multiple embryos. A single cell is taken from each embryo and tested for carriers of the disease, and only healthy embryos are implanted ("returned") to the woman's uterus. The traditional technology for genetic testing of embryos relies on the review of a single mutation or individual mutations. But in recent years, new technologies make it possible to read the complete DNA sequence (genome) of the embryo or most of it. At the same time, large studies were recently published that found a connection between thousands of mutations and features such as height or intelligence, which should enable the ability to predict a person's feature based on their DNA sequence.

The possibility of predicting traits using a genetic "score", even if not precisely, causes great interest in the scientific community and the public. Among other things, the possibility arises to calculate a genetic "score" for features such as height, weight, or IQ for those embryos created in IVF, and to choose the embryo with the best score - for example, the tallest or the smartest. Selection of embryos based on genetic information raises many ethical controversies and is therefore prohibited in most countries (including Israel), but not in the USA. However, the method also has the potential to improve the quality of life and health of the next generation. Either way, since the technology that enables selection of embryos for traits is new, there is no telling whether the method will work. If a couple wants to create embryos in IVF and select the embryo with the highest genetic score for a trait such as IQ, how much "smarter" will the offspring be?

A new study led by Dr. Shai Karmi from the Faculty of Medicine at the Hebrew University, examined the effectiveness of selecting embryos for the purposes of genetic "improvement" based on the means available to science. Dr. Karmi: "In our research, we evaluated the expected benefit of embryo selection by using several methods. First, we ran simulations based on the genetic information of several hundred individuals (from previous genetic studies), in which we paired two individuals and created genomes of their expected embryos on a computer. We checked the genetic score of each embryo for height or IQ, and took the embryo with the highest score. We checked what the expected difference in height or IQ is between the fetus with the highest score and an average fetus. After that, we verified the results with the help of a mathematical model that predicts the difference based on statistical principles of the inheritance of traits."

The results showed that the expected benefit from embryo selection is relatively small. Choosing the embryo with the highest height score out of 5 embryos (a typical number for IVF treatments) will lead to an average increase of only about 2.5 cm in the height of the selected embryo in relation to the average embryo of the same family. Choosing the fetus with the highest score for IQ will lead to an average increase of only about 2.5 IQ points compared to an average fetus (the similarity between the numerical values ​​of height and IQ is a mere coincidence). Even if the experiment is performed with a larger number of embryos, we will get similar results. Choosing the best of 10 embryos will lead to an average increase of 3 cm in height or 3 IQ points only. Further increasing the number of embryos (which is almost impossible to achieve in an IVF procedure), will raise the trait at a very slow rate, so there is almost no benefit in this channel.

Since there are parents for whom even an increase of 2-3 cm or IQ points would be significant, the question arises to what extent it is possible to guarantee that this increase will actually occur. Dr. Karmi explained: "The answer is that the aliyah is not guaranteed at all." It is possible that in a certain family, the selected fetus will grow to be 10 cm taller than the family average, but in other families, the fetus will not only not be the tallest, but will even grow to be shorter than the average. The benefit of performing the genetic test depends on many factors beyond the control of the parents. Traits such as height or IQ are also affected by many genetic factors that are unknown to us as well as environmental factors that we cannot predict."

Since there are ethical problems in research on embryos, Dr. Karmi and his partners used data from a recently published genetic study of the Jewish population that determined the DNA sequence and height of participants who came from families with many children. The researchers examined the genomes of the siblings from the same family as if they were embryos, selected the most successful "embryo" from among them and compared the results to the height of the siblings in reality, when the others are already adults. According to the results of the experiment, the sibling with the highest genetic score was only the highest in a quarter of the cases. In the rest of the cases, the brother with the highest score (ie the one who would have been chosen if it were embryos) was not the highest, and in five families he was even lower than the average. Uncertainty would be even greater for IQ, as it can be predicted with much less precision than height.

Dr. Karmi: "There are many other factors that will lead to uncertainty or a much smaller increase in the feature than the model we proposed. First, the number of embryos obtained in an IVF cycle can be very small, and a significant part of the embryos will not lead to pregnancy and birth at all. In many cases there is not more than one embryo, so it is not possible to choose at all. Second, the actual predictive ability of the genetic scores is expected to be significantly smaller than what has been reported so far in the literature. Also, parents are unlikely to stop at one feature. If all embryos have already been genetically sequenced, why not select the best embryo for both height and IQ or other traits? But it turns out that the more features you add, the smaller the benefit for each feature. For example, if you select the fetus with the maximum score for height and three other (independent) traits, the average increase in height of the selected fetus will be only half of the increase if we had only selected height. It should also be remembered that when parents choose embryos based on a certain trait, it is impossible to know which unwanted traits or diseases they will choose at the same time."

2 תגובות

  1. When will it gain momentum? The time has come for Bibi to invest in this as he invested in bringing the vaccines and convincing the population to take them as soon as possible.

  2. This interesting article describes the current situation,
    from the article
    "Based on the means available to science,"
    And "traits such as height or IQ are also influenced by many genetic factors that are unknown to us as well as environmental factors that we cannot predict."
    It is clear that there is a genetic component even if it is influenced by the environment, it is a fact that there are high families and there are low families and the feature that is even more difficult for us to admit that there is also a genetic component is the level of intelligence, it is not only the environment even if we do not know where it currently sits in the genetic system with all the parts it has,
    It is only a matter of time until the ability to identify, including the ability to change, will reach levels of control that will change the human race forever, man's greatest resource is his intellectual ability once the ability to control the genome
    When they mature, no treaty will stop it, on the contrary, it will become a global competition, the people who control it will achieve dominance
    Globally, imagine a nation with millions of people at the level of Einstein and above, what power such a nation would have
    Compared to other nations if they do not participate in this race, even among individuals there may be such a race between those who have means and those who do not have means if the changes will be very expensive, if so it is likely that the price will be low in the future so that the majority of the population will be able to create a change in their own children. After the first phase of eradicating genetic diseases is over, we may be like electronic systems that are upgraded every year.
    If there are those whose ideology prevents them from participating in this race
    They will condemn their children to backwardness and misery with an inability to integrate into the general population
    In order to achieve happiness in life they will have to break away from the general population like another species.

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