DNA Will Tell: How and Why Paternity Is Established

THE THEME OF DEFINITION OF PARENTHOOD IS LIKE TO BE EXPLOITED in serials and television shows, and recently the whole world has spread around the story of the exhumation of the body of Salvador Dali at the insistence of a woman who called herself his daughter. True, the paternity of the great artist was not confirmed. We will understand how paternity tests work and what results they can show, together with experts: Executive Director of Medical Genomics Marina Demidova and geneticist of the Invitro laboratory Olga Kokorina.    

Who conducts paternity tests and why 

According to Marina Demidova, about three thousand tests are done in Russia per month, which is several times less per capita than in Europe and America. Our market is not saturated, and many potential consumers simply do not know that a paternity test is easy, inexpensive and very accurate. Now the market is growing and will be in the growth stage for a long time. A small part of the samples are sent for analysis to foreign laboratories (mainly in the USA), but 90% are made in public and private laboratories located in Russia. Olga Kokorina notes that the number of studies on establishing paternity is increasing every year, because such tests began to be talked about publicly and the awareness of patients about such services began to grow. In “Invitro” test for the establishment of paternity and maternity are taken monthly from 50 to 100 people throughout Russia. 

Absolutely different people apply for paternity tests, each with their own story – most often painful. Doctors have to not only consult a person, but often delve deeply into the family situation. Many people want to make sure that they pay alimony to their child, and not someone else’s, some establish kinship in order to enter the child in the documents and formalize paternity. Often, men turn to who suddenly have grown-up children. There were cases when people came to the laboratory on the way from the hospital. And sometimes the woman herself tries to understand from whom she has a child, since during the period of conception there were several sexual partners. Frequent clients are grandmothers who do not trust their sons’ wives. They either do a test to determine the relationship between themselves and the grandson, or provide biomaterial from the alleged father, and often secretly from himself. This is also possible – Demidova says that paternity had to be established on toothbrushes, cigarette butts, pacifiers, chewing gum, cutlery and even dried semen, although a smear from the inside of the cheek is considered the standard biomaterial. 

How is the analysis done

Each human cell contains forty-six chromosomes. The exception is germ cells, that is, eggs and sperm; they have exactly half the number of chromosomes, twenty-three each. When they combine and an embryo is formed, everything in its cells is like an adult: forty-six chromosomes, half from mom and dad. Therefore, the DNA of the child is half the same as the DNA of the mother and half with the DNA of the father. This law is the basis of the paternity test. 

How inherited genes will manifest themselves is impossible to predict. Appearance is a phenotype, that is, a set of traits that determine how a person looks. Genes, of course, affect him, but more difficult than you might imagine after a high school biology course. In the problems about peas and fruit flies, everything was simple: exactly the same mushata were born from a fly with striped wings, and yellow peas did not produce green offspring. The human structure is much more complicated, we have more genes (including those whose functions are still unknown), therefore the result of the influence of the genome on appearance is unpredictable. The child can be a copy of the mother, a portrait of the father, or it can be something like a great-great-grandfather, from whom not even a single photograph remains.

But the analysis of the gene sequences will still show from whom the child received his chromosomes. To conduct testing, you first need to get samples of cells containing DNA – it is found in all cells of the body, and it is not so difficult, but some types of material are easier to work with. Therefore, now saliva or scraping from the inside of the cheek is most often used for analysis – it is simple, painless and does not require special costs. Since everyone can collect saliva on a cotton swab, this method of obtaining DNA is used in “home” genetic testing kits : you collect a saliva sample and send it by mail.   

In Russia, too, there is a tendency towards home collection of biomaterial – and, according to Marina Demidova, this repeats what is happening in Europe. For example, in England now only tests with personal identification for the court are done in person in the laboratory, and all informational examinations are carried out with the help of self-taking biomaterial and sending it to the laboratory by mail or by courier. To pass the paternity test, it is enough to receive a set by mail, pay for the analysis online and send the biomaterial to the laboratory. The process is so simple that more and more people are using the method. Although many still prefer to come to the clinic in person, even for a routine information test without personal identification.

Of course, both blood and other tissues can also be used for testing – as, for example, in forensic science, where DNA is determined by what it has to do. After the samples are received in the laboratory, the researchers do PCR (polymerase chain reaction), which means they make multiple copies of DNA. Then it will be easier to compare them with a database – or, if we are talking specifically about establishing a relationship, with the DNA of another person. The more matches are found, the higher the degree of kinship between people. Thanks to such testing, it is possible to confirm not only paternity or motherhood, but also more distant family ties – however, in such cases, it is only possible to determine that people are distant relatives, but not to establish exactly who has whom. The test takes about two weeks and costs about fifteen thousand rubles. 

How accurate is DNA analysis

Although we rarely talk about one hundred percent accuracy in medicine and biology, it is precisely this that the result of DNA analysis comes close to. If the samples match, then rechecking them is pointless – except to suggest a complex story in the spirit of soap operas about separated identical twins claiming paternity. Theoretically, the human factor remains possible – for example, someone mixed up the samples and the result turned out to be negative, but this is again a theory that is closer to the plots of melodramas than to life.

Testing laboratories care about their reputation: after all, the issue of establishing kinship is delicate, and its results can change people’s lives. It is unlikely that it is profitable for laboratories to lose money invested in equipment due to rumors about inaccurate results. For the same reason, tales of how someone bribed a lab and tampered with a test is unlikely. Be that as it may, any doubts are resolved by repeated analysis in the same or a different laboratory. A double positive or double negative result eliminates the possibility of error. 

Is it possible to check paternity without a father

It is most convenient to check the relationship, of course, “in a straight line”, between children and parents – in this case, everything is simple. It is enough to compare two regions of the genome, and the number of coincidences will speak for itself. But you can also define another degree of kinship – for example, between a grandmother or grandfather and grandchildren. In this case, the number of matched loci will be less than when comparing samples of children and parents, but much more than when comparing the genome of two people who are not related. Of course, the paternity of a particular person is not directly confirmed – it will still be necessary to prove that there are no other options for kinship between the tested people.

Is it possible to determine paternity during pregnancy

In some cases, the question of genetic testing arises during pregnancy – and there are several ways to do this. Widely known – with the help of amniotic fluid. It always contains embryonic cells, from which the DNA necessary for analysis is isolated. The obvious disadvantage of this method is its invasiveness: in order to take the amniotic fluid, you need to carry out the amniocentesis procedure, that is, to penetrate the membranes. This increases the risk of termination of pregnancy. Another similar method is a chorionic villus sampling, in which tissue from the placenta is taken for analysis. This is also an invasive procedure that can lead to miscarriage.   

But there are also methods that do not require such complex operations. In 1997, it was revealed that the blood of a pregnant woman contains fetal DNA, and now laboratories are offering options for a non-invasive prenatal test. They are made from the ninth week of pregnancy, they are safe for the fetus – however, they cost much more than any other test to identify family ties. In addition, this technology is not available in every laboratory because it is relatively new. By the way, this method of isolating embryonic DNA has another application: early gene analysis reveals fetal abnormalities, chromosomal abnormalities, such as Down’s syndrome, and does this more accurately than ultrasound and other methods.   

What the study results say

When it comes to fatherhood or motherhood, the results are accurate: the relationship is either confirmed or refuted. The results can only be like this, that is, laboratories do not make assumptions and do not try to guess how the people who brought the material for analysis can still be connected. There is no third option in matters of paternity or motherhood, but it appears when it comes to establishing kinship between, say, sisters and brothers, cousins, and so on. If the DNAs coincide in the required number of parameters, then the result sounds something like “kinship is possible”, if not – “kinship is unlikely.” But if there are not many and not few coincidences, then the result may be uncertain.

Analyzes can be taken anonymously, that is, the results will indicate abstract persons A and B and the degree of confirmed relationship between them. Only anonymous analyzes mean nothing for the court – and quite often the court generally recognizes the results of only those analyzes that were ordered by its decision. If paternity is established in court, then, most likely, you will have to go through an official examination. The process itself will not differ from the usual analysis, except for the peculiarities of paperwork – and, of course, anonymity in this case is out of the question.

local_offerevent_note July 28, 2021

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