What genetic tests will tell and what will remain silent

People far from medicine know little about genetics. But almost everyone has heard that all information about the human body is recorded in DNA. This means that the main thing for doctors is to correctly decipher the genetic code, and they will not have problems with treatment.

A person gets sick - genetic tests will help choose the most effective medicine. And at the same time they will show which dishes will be the most useful for the patient, so that he recovers, is strong and energetic.

What of this is true and what is fiction, geneticist Irina Zhegulina told at the forum "Scientists against myths". Recording of her speech posted on the organizer's channel ANTROPOGENESIS.RU, and Lifehacker made a summary.

Genetic tests do not always help determine ancestry

Many people take tests to find out exactly who they are by nationality. And in vain.

Geneticists know: analyzes allow you to determine the haplogroups that a person got from parents. This information can tell about its origin. Each of us has two main haplogroups:

• Mitochondrial, which is transmitted through the maternal line. It is necessarily detected in both men and women, since mother's genes go to all children. But men cannot pass it on – that is the function of a woman.
• Y-haplogroup - transmitted only through the male line. That is, from the grandfather to the father, from him to the son, and then, together with the Y-chromosome, this genetic information will pass to the grandson. Women don't have it.

There are territories in which the same Y-haplogroup prevails. Hence, it can be concluded that ancestors a person with this form lived in a specific geographic area. For example, a large number of people with haplogroup R1b live in France, Spain and Great Britain.

And men with haplogroup I1 are often found in the southern half of Norway and Sweden. This means that if a person has these haplogroups, his male ancestors could come from there. But it is impossible to name the country exactly.

The mitochondrial haplogroup helps to find out how the human ancestors settled on the planet on the maternal line. Usually it points not to one region, but to several. Moreover, they can be located in different parts of the globe. For example, similar haplogroups can be recorded in northern Africa, the Far East, and North and South America.

No study will be able to say exactly how many percent a person has. blood one ethnicity or another. Test results are compared only with averaged data - moreover, with those that are in the database of a particular company. They will show how similar a person is to the average Estonian, Russian or Swede, nothing more.

Genetic tests help to find out about hereditary diseases that threaten a person

Yes it is. With a small correction: no study can guarantee a 100% result, because each diagnostic method has its own limitations. There are mutations that are not able to detect even the most expensive and high-quality analysis.

There are a few more limitations to genetic testing. Here they are:

• No genetic analysis can predict new mutations. That is, dad and mom are perfectly healthy, and no one expects trouble. And a child can have a de novo mutation - the first in the family. Such changes in DNA not uncommon, each of us can have them. But we don’t even know about them, because most of these mutations do not lead to serious diseases. But there are rare cases when change is still dangerous.
• It happens that there are mutations in the body, but they do not appear in all cells. For example, there is such a genetic disease when spots of the color of coffee with milk appear on the skin of a person. If they are, then the probability of occurrence of various tumors - both harmless benign and dangerous malignant. But changes in DNA do not appear in all cells of the body, but only in some of them. That is, you can take saliva from a person for analysis - and the test will not show anything. And if you examine the skin cells, you can identify a mutation.

With regard to diagnoses such as diabetes mellitus or hypertension, it's not that simple either. Yes, there are some genetic indicators that allow doctors to conclude that a person has a predisposition to the disease. But this does not mean that he will definitely get sick.

The development of many chronic ailments depends not only on heredity, but also on lifestyle. Therefore, genetic tests will help to warn a person. But they won't predict whether he will stay healthy or be forced into treatment.

Tests will not help you choose the ideal diet and diet

Based on the results of the analyzes, it is impossible to draw up a complete diet that is useful for a particular person. It is a myth.

But tests can show how the body perceives certain foods. For example, milk sugar or caffeine. You can find out if digestive disorders when drinking milk. Determine how quickly the body will process and remove the portion of alcohol that someone drank at dinner. Conclude how safe foods with gluten are for humans.

This is important knowledge: they will tell you which products should be discarded. But they will not help to come up with a diet that would be most useful to a particular patient. This question is not decided by genetics. The main thing here is motivation and general knowledge about good and bad eating habits. Well, the desire of a person to stay healthy as long as possible.

Genetic tests will help to pre-evaluate the effectiveness of the drug

Doctors know how to determine in advance whether a person should be prescribed drugs from a fairly large list of drugs. So far, it includes about a hundred medicines.

If you take a group of people with the same diagnosis and give them one drug, the majority will say that the drug works well. But some people will notice that the remedy works poorly or does not work at all. Well, some will feel that it has become worse - side effects have appeared.

Geneticists can determine how effective a drug will be for a particular person. Fortunately, this is not a myth. For example, there is such a group of drugs - statins. They help control levels. cholesterol in blood. But some patients refuse to take them - they are afraid of serious side effects.

Scientists were able to establish that a very small change in DNA greatly affects the tolerability of one of the statins - the drug simvastatin. There is this change - the risk of a destructive effect of a substance on muscle tissue increases. No change - all is well. This means that it is possible to offer the patient to undergo a genetic test before prescribing such drugs. And to determine whether undesirable effects will appear or you can safely drink pills: there will be no side effects.

Genetic screening won't tell you how good people are for each other

There is such a myth: genetic tests will help determine whether people will live together happily ever after or if they should not meet at all. This statement does not correspond to reality at all: no tests will show whether people are suitable for each other.

But couples entering marriageHowever, genetic testing is still worth it. And to see if there is a danger of any hereditary diseases in children.

Future parents can be perfectly healthy, but at the same time be carriers of rare genetic diseases. Scientists believe that each person has up to three of these mutations. Maybe people will never know about it, and the diseases will not manifest themselves in any way. But there is a possibility that the mutations in both parents will coincide. Then there will be a risk of having a child with a pathology. According to statistics, such a danger can lie in wait for one family out of 50-100.

Therefore, future parents before conception should do genetic tests. Not to break up or divorce if the doctors see danger. The goal is different - to control the process of fetal development and not to miss violations if they occur. Maybe doctors will advise you to regularly take certain tests during pregnancy in order to identify pathology at an early stage. Or maybe they will immediately recommend an IVF procedure.