Parentage reports
The parentage certificate is the result of a scientific procedure, with which the relationship between people is to be determined. The procedure is called because of the common use case in the current language paternity test referred to, but is sometimes called maternity test , paternity testing , in the opposite case as paternity exclusion procedure or as Paternitätsanalyse referred.
Methods
The methods of parentage assessment have evolved with the advancement of science. There are u. a. the following methods:
- When blood tests are blood types of the mother , the child and the alleged father determined. The well-known inheritance rules rule out a number of result combinations.
- In serological reports (more blood components are HLA - antigens and other proteins ) drawn into the investigation.
- In anthropological and hereditary biology reports , the probability of paternity was checked with the help of heritable external characteristics (e.g. skin, eye, hair color, head shape, iris structure).
- The DNA analysis is the most modern and safest method of ancestry testing. It can also be performed prenatally because free fetal DNA can be detected in the blood of pregnant women.
Plausibility check based on visible features
The assessment of anthropological differences is the oldest available method. This is a plausibility check in which existing knowledge about parents and offspring is compared with known inheritance rules and statistics. This method cannot finally exclude offspring as a rule, since parents can still pass on genes that are not phenotypically pronounced ( phenotype and genotype ), so that the child shows visible characteristics that are not visible in the parents. Due to the phenotypic plasticity, including the influence of the environment and illnesses suffered in the course of life, dominant genes can also be expressed differently.
- Hair color - when it comes to hair color, dark brown is dominant to blonde, so that even dark-haired parents can have blonde children. Similarly, red hair recessive in brown instead of melanin , the lighter pheomelanin forms the pigmentation.
- Eye color - blue eyes are recessive because a light blue, like infants, does not actually contain any pigmentation. At least three genes are involved in the inheritance of eye color, the function of which is not yet fully understood.
- Body size - the attainable body size depends not only on the genetic constitution but also on the diet, especially the protein intake. The mean value of father and mother plus / minus 6.5 cm for sons / daughters is actually statistically probable.
- Skin color - the limited state of research into the genetic basis of skin color indicates that most of the differences arise from variations in the receptors for pigmenting melanin. So far, 18 genes have been identified for Europeans that make a contribution; in Africans there are populations that do not show any variation in any of these genes.
It is precisely the external characteristics of a child that often give the original reason to question paternity. However, the examples on the genetic basis show that even large differences are only unlikely, but do not provide a reason for exclusion. The coincidence of several large differences is less likely, but the intuitive understanding of probabilities is sometimes significantly different from the known probability calculation .
Elimination process based on a blood group test
Blood group tests determine the blood groups of the mother, child and the presumed father. It is then checked whether a common offspring of the mother and the father could have the same blood group as the child. This procedure can only exclude paternity in certain combinations , but not confirm it.
The inheritance rules for blood groups in the AB0 system are fully known - and in contrast to the Rhesus factor , the antibodies are also spontaneously expressed in all children in the first year of life, which can be easily detected using an antibody test . The tests for blood type in the AB0 system and Rh factor D are widely used, including a bedside test . Compared to DNA analyzes, blood grouping is cheaper and adults can easily find out the blood group free of charge by donating blood . The blood group of an unborn child can be determined without any risk to the pregnancy, since a small part of the child's blood cells are also present in the mother's bloodstream and can be differentiated there - an intervention as in prenatal genetic diagnosis is not necessary here.
Every person has a genotype in the AB0 system with exactly two alleles from the total of codominant allele A and allele B with the recessive allele 0. The genotype of a child is made up of exactly one allele of the mother's genotype and exactly one allele of the genotype dad's. There is no popular inheritance of the phenotypic blood group, a child of parents with blood group AB (genotype AB) and 0 (genotype 00) must either have blood group A (genotype A0) or blood group B (genotype B0). Other blood groups are not possible from this parent configuration (here AB or 0). With other parent configurations, knowledge of the grandparents' blood groups can often exclude some genotypes.
Parentage assessment based on a DNA analysis
The genetic fingerprint allows a person to be identified based on features of the DNA. In the course of the parentage assessment, one uses the inheritance rules that in the diploid genome of humans for each gene one allele must come from the father and the other from the mother. If features appear in the DNA strands of the chromosomes that are not present in the parents, then parenthood can be ruled out. Since there are a number of possible errors in the biological inheritance , including mutations acquired during life, several characteristics are included in the DNA analysis in the course of the parentage assessment and summarized into a probability number of the parentage. Since the genetic fingerprint focuses on areas that show a high degree of variability in the total population , the DNA analysis can also confirm parenthood with a probability number .
As a rule, no coding sections are examined for the parentage reports , only the areas between the genes are analyzed ( repetitive DNA ). Therefore, the examinations of these DNA areas are not regarded as particularly protected areas within the meaning of the Genetic Diagnostics Act , but taking samples from children is an interference with the right to privacy . In Germany, therefore, the obtaining of a parentage certificate based on DNA analyzes was regulated by law.
