How far did the apple fall

Geneticist Olga Shchagina on why "all in the father" is no longer an argument

Victoria Filatova, "Evening Moscow"

We continue our heading "Simple questions", in which we ask professionals about what we don't know for sure ourselves. Which came first: chicken or egg? When will scientists come up with a remedy for all diseases and should a dark-skinned dad panic if a blond and blue-eyed baby was taken out of the hospital? And if the egg issue is still debatable, then the geneticist Olga Shchagina knows everything about diseases and babies for sure.

Recently, everyone has been waiting for miracles from genetics. Blog and media headlines compete in sensationalism, promising that "scientists have found the gene of youth" or "reprogramming of genes will rid a person of all diseases", and "a third eye will appear from GMO products"! Much of what is discussed by "sofa geneticists" makes Olga Shchagina, Candidate of Medical Sciences, smile. Scientists generally do not tend to believe in miracles, seeing behind each "miracle" a carefully prescribed formula or statistical exception.

— Olga, how accurately can popular genetic tests determine the nationality of ancestors?

— No genetic test will definitely answer the question of what nationality you are. Simply because this concept is more geopolitical than genetic. The processes of settlement of people across the territory, marriages, geographical or social isolation of individual groups of people leave traces in the DNA: changes accumulate that occur more often in an isolated group of people leading a sedentary lifestyle, and less often in nomads.

Therefore, geneticists can determine that a specific genotype from the studied markers is most often found in the Mediterranean group of peoples or in the inhabitants of Alaska. But it is impossible to say that your ancestors with a probability of 100 percent were from the shores of the Mediterranean Sea. They could have been born somewhere in the mountains, into which a group of coastal residents climbed several generations ago, bringing their gene pool to the settled population. Therefore, the genotype of the inhabitants of such settlements will differ little from the genotype of the Mediterranean peoples leading a sedentary lifestyle. And they could have fled from one continent to another as a result of war or climate change. Well, how can you determine nationality here?

— Is it possible to know in advance the chances of having a child with pathology?

— It is impossible to exclude the birth of a child with pathology by 100 percent. It is possible to reduce the risks through research on the carrier of private hereditary diseases. So, there are hereditary diseases that manifest themselves only if the child has inherited both copies of the damaged genes from mom and dad. And since the second gene of the parents is intact, they are carriers that remain healthy. There are diseases for which the frequency of carriage is quite high, for example, cystic fibrosis or phenylketonuria. It is possible to determine whether future parents are carriers of frequent diseases at any time in a person's life, for example, when planning a pregnancy.

However, even if both parents are carriers of a genetic disease, this is not a reason to panic. Their child will be born healthy with a 75 percent chance! On the other hand, even if future parents are not found to have frequent hereditary diseases, this is not a guarantee that the child will be exactly healthy. More than half of hereditary diseases are not inherited, they arise as a result of a breakdown in the cell of a new organism. This situation cannot be prevented. 1-2 percent of people in the population are born with hereditary pathologies. Every person has this risk.

— Is it possible to edit genes so as to avoid all diseases?

— In order to edit genes, it is necessary to deliver a genetic construct to every cell of the body, of which we have a lot. It should effectively penetrate into the cell, then into the DNA, effectively change this DNA and at the same time not harm the body. This is an extremely difficult task. Even if we know what and how to edit, it is problematic to do it efficiently and safely today. Well, besides, not all diseases are related to genetics, many develop under the influence of lifestyle. To be honest, it's easier to edit your lifestyle to avoid most diseases.

— If an application like Tinder appears that allows you to select a couple based on a similar genotype, will it help people to form alliances faster?

— From the point of view of genetics, the more differences in genes, the better. Therefore, for a long—term relationship with the subsequent birth of children, it is best, on the contrary, to look for a partner with a completely different genotype - this can reduce the risk of meeting two carriers of genetic diseases. However, people themselves prefer assorted unions, choosing people similar to themselves as partners.

As for falling in love in general, then, I'm afraid, genetics alone will not be enough. Our body is a large physico—chemical factory, in which many processes related to perception, vision, and smell occur simultaneously. At the biochemical level, there are still no objective studies of why one fits the other. And if there are no answers to these questions from chemistry, then it is pointless to look for answers from genetics.

— Is it true that intelligence from the father can only be passed on to the daughter?

— That's not true. Intelligence is a combination of physical, chemical, cultural and biological factors. And all these factors cannot be explained only by genetics, and even more so it is impossible to explain the genetics of one chromosome. The only thing that is passed from father to daughter and not passed on to son is the X chromosome.

— Profilers have tests that supposedly can determine a person's psychotype by the shape of fingers, for example, or the shape of ears. How much is this possible?

— In the body, a violation of one gene can lead to a change in several signs at once, since the same gene works in different tissues and organs. For example, a person may have short fingers or an unusual skull shape. So external features can really be related to intelligence. They are often described as part of hereditary syndromes, such as, for example, Down syndrome. Does it happen the other way around when external features speak of some superpowers? Probably, it also happens, it's just not described in the syndromes.

If we are talking about ordinary people, then you need to understand that folk signs also work. For example, if swallows fly low, it will rain. Why? Because people have been watching this for several hundred years. The same can be said about some phenotypic features. The only question is probability. How likely is it to rain if the swallow is flying low — 50 or 70 percent? It's the same with the shape of the hands and ears.

— Can GMO foods change genes?

— They can't. To begin with, the product that enters the human body naturally goes through several stages of harsh chemical processing: mechanical grinding, acid splitting, and so on. Accordingly, processing in an aggressive environment almost completely destroys a complex molecule. Do you remember when we discussed gene editing, we said that humanity is working on it, but still can't figure out how to efficiently deliver the material to the cell so that it can edit something? The fact is that the cell has a double shell, and a single DNA or RNA molecule has no mechanisms to penetrate it. Therefore, the only harm that GMO products can cause is allergic reactions to proteins unfamiliar to the body. But as a rule, there are no such proteins in approved products: they are all tested before they get to the shelves of stores.

— Is bad character inherited?

— There are some genetic variants that determine the characteristics of character and psyche. Some features of reactions can be inherited. But it is so difficult that it is impossible to predict it using genetic analysis. The environment affects a person's character much more than genetics.

— The red gene is considered recessive, but why do the brunette Meghan Markle and the red-haired Prince Harry both have red children?

— Oh, from the point of view of genetics, everything is simple here! Each person has two copies of each gene: one pair is obtained from mom, the other from dad. Accordingly, if the gene is dominant, then it will manifest itself, even if it is on the same chromosome.

For example, I have two pencils — dark brown and light yellow. If I paint them at the same time, I will get a dark color. And I will get a light color only if I have two yellow pencils in my hands. But at the same time, if we combine a pair of two yellow pencils and a pair of yellow with a brown pencil, then with a probability of 50 percent we will get a combination of two yellow pencils, and in our case — a red-haired child. Moreover, these probabilities do not accumulate: the birth of each child is independent. Therefore, considering the Irish red—haired ancestors of the dark-haired Megan (brown and yellow pencils) and the red-haired Prince Harry (two yellow pencils), the probability of having a red-haired child is 50 percent.

— Which ethnic groups have a greater number of accumulated pathologies compared to others?

— Ethnic groups isolated from the big world, for example, living somewhere on an island, and those where only related marriages are the norm. Such peoples have a high probability of the appearance of some hereditary diseases. But if a representative of an isolated ethnic group goes out into the big world and gives birth to children with representatives of the big world, then the likelihood of his children having hereditary diseases will decrease. The further apart the parents are genetically from each other, the less likely it is that their child will have some kind of recessive disease.

— What genes are responsible for the predisposition to alcoholism in the peoples of the Far North and a good alcohol metabolism in the inhabitants of the Mediterranean?

— Two main enzymes are responsible for the metabolism of alcohol: alcohol dehydrogenase and aldehyde dehydrogenase. These enzymes can have fast and slow forms. Alcohol dehydrogenase quickly converts ethanol to acetaldehyde, and aldehyde dehydrogenase destroys acetaldehyde and removes it from the body.

With a small amount of alcohol, our body does not care what variant of these enzymes it has, because both forms will have time to process it to safe products without harm to the body. And when it comes to large doses of alcohol, the speed of work is already important here. Accordingly, there is a variant in the genes that makes the work of enzymes fast in some people, and slow in others.

The inhabitants of the Far North have accumulated some gene variants, and the inhabitants of the Mediterranean have others. But you can't explain everything only by genetic predisposition. There are also cultural, nutritional and social characteristics that affect the predisposition to alcoholism.

In general, genetics easily gives a prognosis for hereditary diseases. But common diseases are primarily influenced by the environment and lifestyle, which can lead to the fact that the predisposition will turn into a disease. And among Italians there are alcoholics, and among the peoples of the Far North there are many teetotallers. A healthy lifestyle is our helper so that we never find out about our genetic risks.

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