A DNA test involves a detailed scrutiny of the DNA composition of an individual, which is unique to that person. DNA is the genetic make up of an individual and it is found in every cell of the body. This chemical is responsible for the genetic instructions required to create an organism that reflects its own unique traits and the ones that are inherited from the parents too.
People undergo DNA testing for various reasons, some of which are genealogical, clinical, and legal purposes. A genealogical DNA test is usually meant to trace the ancestry of an individual, and for comparing results to know the historical and geographical origins. This test is usually for research purposes, especially in population genetics.
These ancestry tests are of two types: Y-DNA test and mt-DNA test. The test values of both the results differ and so do their methods of interpretation. In the Y-DNA test, maximum matches are preferred, whereas in the mt-DNA test a perfect match is expected for proving a direct relationship to the mother.
DNA tests for clinical purposes usually give out a genetic map of an individual. This map marks the genes present in the entire DNA sequence. It shows the genes that are responsible for certain diseases or disorders, if they are present or triggered. It serves as a warning to avoid certain diseases that may be fatal or inheritable, in turn avoiding its presence in present and future generations with the help of proper genetic counseling. This test can never be gauged on the basis of "values" as the results are usually interpreted on the basis of the genes present, their function, action, and reaction.
Tests carried out for legal purposes usually involve paternity tests. These tests involve comparison of a father's and son's DNA samples and sometimes the samples of other family members too, in order to identify paternity and identity. This test's result is given out in the form of a DNA profile that includes the combined parentage index, probability of the relationship that involves paternity, maternity and beyond, which indicates the strength of the relationship biologically. For legal purposes, there are some values set for the accreditation of these tests to be used as proof while resolving paternity disputes.
Hence, the values of these tests vary as per the test performed and the intention for which the test is being conducted. DNA tests happen to be the most accurate when looking for specific results and can be very subjective if used for aspects that require a broader perspective that goes beyond generations in count.