Determination of paternity is rather a legal procedure, necessary, for example, in the case of a divorce proceedings in order for a woman to obtain the right to alimony. However, the reasons why such a procedure is necessary are sometimes quite delicate.
The most commonplace, but also the most inaccurate way of determining paternity is by external signs. That is, if both parents have blond hair and blue or green eyes, then their child will wear the same external signs. This does not take into account the fact that some genes can manifest themselves through a generation, and parents can be its carriers. For example, two dark-haired parents may well have a red-haired child if they are the ancestors of one or both parents with red hair. Therefore, instead of abandoning the child right away on the basis of the "wrong" hair or skin color, new parents should first ask their dads and moms.
The method of determining paternity by external signs is also untenable due to the existence in nature of people who are very similar to each other, who do not have any kindred ties.
Determination of paternity is also possible on the basis of the gestational age. It is believed that the greatest probability of conception occurs in the middle of the menstrual cycle, but in practice this is not at all a significant indicator - on other days fertilization is also more than likely. The ultrasound procedure can, with relative accuracy (up to a week), determine the time of conception based on the degree of fetal development. But only if a woman had several partners for several weeks of the menstrual cycle, this method will be useless.
Several decades ago, the most accurate determination of paternity by blood group was considered. Of course, analysis can only be taken from a child who has already been born. As you know, a person has four blood groups and a positive or negative Rh factor. Therefore, logically, a child should have a blood group of one of the parents, but this is not the case. Studies have shown that in people with the fourth blood group, the baby can have anything other than the first. And if one parent has a second group, and the other has a third, and at least one of them has a positive Rh factor, then the child's blood can be absolutely any. In general, this method at least allows you to refute paternity with very high accuracy, but for confirmation it is no longer the best option.
Any paternity testing requires input from both parents and the child. If the latter is under the age of 18, the non-initiating parent must write a written authorization to administer the test.
With the development of genetic engineering, the DNA test has become the best option for determining paternity (which can also be used in court). Unlike external signs and blood groups, where the number of combinations is quite small, DNA is unique for each person. The test is very expensive - from 12 to 25 thousand rubles, the price varies depending on the number of chromosome regions (so-called loci) that will be examined. It is clear that a larger number of areas to be examined increases the accuracy of the results up to 100%. The test requires a small amount of genetic material - blood, hair, nails, or scraped skin cells. A sample is taken from an unborn child by other methods (for example, a biopsy), which, however, can complicate the course of pregnancy. DNA samples can be taken from a dead body, which is important in matters of inheritance division.
