The uncle/aunt test, also known internationally as avuncular test, is basically a paternity or maternity test, where specific polymorphic DNA markers are analyzed to determine the statistical probability (likelihood ratio) that a person is the biological aunt or uncle of the child, instead of determining direct parental relationships. The DNA test for aunts or uncles allows the brother or sister of an alleged father to participate in a DNA test in order to confirm or exclude the biological relationships. Since we all inherit genomic information from both our parents, who, along with their brothers and sisters, they too inherit their genetic material from their parents, our genetic material reflects our biological relationship with our aunts and uncles.
DNA profiling for aunt/uncle relationship testing – Avuncular DNA test
Unlike a classic paternity DNA test, which always provides a definitive result with a probability of >99.99%, the uncle/aunt test (avuncular test) is somewhat different. In an avuncular test, the laboratory will determine the DNA profile of the individuals and a statistical indicator-likelihood ratio is derived based on the observed polymorphisms. If this ratio is equal to or less than 1.00, this indicates the absence of a grandfather-grandmother-grandchild relationship, whereas if the ratio is greater than 1.00, it indicates that the two individuals are more likely to have a biological relationship of grandfather/grandmother and grandchild. A high likelihood ratio value indicates a high probability and therefore we often need to analyze many polymorphic markers (e.g. >30) in order to reach the maximum value.
Depending on the case, we use several dozen internationally accepted and validated polymorphic STR markers (at least 30) and also other polymorphic STR markers of the X and Y chromosomes, in order reach the highest possible degree of probability (likelihood ratio). For the calculation of likelihood ratios we use a special software and the necessary STR frequency database in the Greek population, ensuring an outstanding reliability for our results.
Especially in cases with male children and a paternal uncle, we can directly test multiple STS markers of the Y chromosome (Y-haplotype) and thus establish or exclude a paternal inheritance/paternity (see DNA profiling for paternal lineage testing), since the Y chromosome is always inherited from father to son and so on.