How is DNA analyzed?

In the laboratory, DNA is extracted from the buccal swabs which is then analyzed. In particular, particular sections of the chromosomes are analyzed, which vary in length according to the individual. These sections are called ‘loci’, (singular locus) and the test takes sixteen of these ‘loci’ into consideration. Detailed analyzes of each of these ‘loci’, drawn from the study of extensive populations, revealed that each of them contains fragments, called alleles, associated with each ‘locus’. These are the genetic markers that are used in paternity tests and other various DNA tests.

  • Paternity test without the Mother – Inclusion.pdf >> click here
  • Paternity test without the Mother – Exclusion.pdf >> click here

Each individual inherits half of his chromosomes from the mother and half from the father, so each individual has two allele parallel to each ‘locus’, one from the mother and one from the father. A paternity test analyzes the length of each of the two allele found at each ‘locus’.

In the paternity test report that will be delivered to you, you will find a series of numbers listed in the first column, each of which represents one of the 24 loci that were analyzed during the test. Below the presumed father and son columns are listed a list of numbers representing the length of each of the two allele found at each ‘locus’.

So if, for example, a child has two alleles that have the numbers 16 and 17 respectively, and if the mother has alleles 12 and 16 respectively, then the child must have inherited the allele 16 from the mother. This leads us to the conclusion that the son inherited the allele 17 from the father. So the alleged father must have this allele to be confirmed as the child’s biological father. This process is repeated for each of the loci considered in the test analyzes.

The paternity index

If the alleged father does not have an allele that corresponds to that of the son at each of the ‘locus’ analyzed, then the possibility that he is the biological father of the tested son is excluded. If you analyze them of the ‘loci’ it indicates that there is a correspondence then the alleged father is confirmed as the biological father of the child. This relationship is referred to as the Paternity Index obtained for each ‘locus’, these indices are combined in total to obtain a single ‘Combined Paternity Index’. This index represents a measure to calculate the “probability of the relationship” which is the percentage of correspondence between the alleles of the presumed father and those of the son.

This Probability Percentage is specified in the results. If the Probability Percentage is 0% this means that the DNA of the alleged father is not compatible with that of the son and therefore it is excluded that it is the biological father. On the other hand, if the Probability of Paternity is compatible, a result higher than 99.99% will normally be obtained.

The results of tests performed on legale DNA samples such as hair, semen, etc. will be presented in the same way as once the sample has been successfully extracted, the DNA analysis process is similar to a DNA analysis taken. from a bucal sample.

For more information on how to interpret your DNA test results, please consult our customer service.