The DNA testing aimed at the genealogical information stored in our DNA may help us to shed a light on our lineage and ethnic belonging. The process of the test is very simple; it is just by sending the saliva sample or the swab from the cheek to the lab for the scientists to analysis. With the high degree of certainty, it can reveal the common ancestry between individuals for up to 5 generations back, and some tests can show your geographic origin going back thousands of years.
There are three different ancestry DNA tests: autosomal (atDNA), mitochondrial (mtDNA) and Y-chromosomal (Y-DNA).
Autosomal test uses the particular sequences of nucleotides, called SNPs and STRs that differ significantly between unrelated individuals but show the degree of similarity among the family members. Each generation shares 50% of those sequences with the previous one, so by determining the exact nucleotide sequence and number of SNPs or STRs scientists can calculate the possible number of generations between the suggested relatives. Sometimes another approach, based on the nucleotide patterns common in certain geographical locations is employed to pinpoint the geographical origin of a client.
Mitochondrial DNA test uses for analysis the DNA stored in the mitochondria (small energy-producing structures inside the cells). This type of DNA gets inherited only from the mother to all of her children unchanged. Thus, mtDNA analysis can give information about the maternal line of ancestry. mtDNA sequences shared by the specific ethnical populations known as haplogroups. Matching client’s DNA with the database of human haplogroups allows to determine the probability of belonging to the particular ethnicity and geographical area of origin. mtDNA test could identify possible maternal relatives even if their common ancestor lived up to 16 generations ago.
Y-DNA testing uses Y-chromosome sequence analysis to confirm the paternal lineage. Y-chromosome passes down exclusively from father to son usually unchanged by mutations. Only men can be tested, the most recent common ancestor (MRCA) can be found many generations back. Test results presented in the form of percentiles, which show how likely the two compared DNA share the same MRCA on each generation level. For example, if there is a perfect match between the two samples, there is a 50% chance that the MRCA was two generation or less ago, 90% chance that it was less than 4 generation ago and 95% possibility that it was fewer than 5 generation back. Women can obtain information about their paternal ancestry line by submitting the DNA sample of their fathers, brothers, paternal uncles, grandfathers or male cousins.
All of those tests analyse only a small fraction of DNA, which carry the most relevant information about the lineage. For example, about 10 to 60 markers on the Y chromosome are usually tested, but there are more than 100 markers available. This strategy helps to minimise the cost and the time needed to perform the test. However, in order to explore the additional links to various populations and geographical locations, larger number of genetical markers can be studied. It is usually helpful to support the genetical data with the traditional genealogical research.