In the case of a great-grandchild, or a great-great-grandchild, something even stranger can happen.  Remember that a child will get half of their mother’s DNA, but there is never ever guarantee which 50%.  The way it is chosen is fairly random, as far as scientists know.  Take the example of the 100% Eastern European person.  Their great-grandchild will inherit 50% of their DNA from their part-Eastern European parent, but there is a good chance that they won’t inherit all of the Eastern European DNA that they could potentially inherit.  It’s possible for a person to share NO DNA with a great-great grandparent, even though there is a verified genealogical relationship.
It’s worth bearing in mind that when you’re presented with the population groups that have contributed to your DNA, some of the groups revealed may be very general (e.g. Western European) and the report may not tell you when or for how long each group was located in the region that it’s named after. The specificity of the population groups depends on the reference populations used by the company you test with (discussed later). Therefore, if a detailed ethnic breakdown is important to you, look for example reports from the company you’re considering, or get in touch with them to ask for a list of the reference populations that they use.
There are many places you can upload your raw DNA, and several of them are free. Popular third-party DNA analysis tools include GEDmatch and Promethese. GEDmatch is a free, open database and genealogy site that gives additional DNA relative matching and trait results. This tool has information from users of multiple different testing companies. Promethease compares your raw DNA information against scientific reports that link certain markers to health conditions, though you should take these results with a grain of salt as genetic links do not equal a diagnosis.
When asked about how database size affects ancestry results, David Nicholson, co-founder of Living DNA, told us, “The tests absolutely rely on the reference database. If you have Polish ancestry but there are no people in the database who are Polish, then what the test will do is show what the next closest group is next to Polish, like German or Eastern European ancestry.” 

I was given a picture of myself I believe I was about two or three years old, I have always thought I was born in the USA, BUT TO THE BOTTOM OF THE PICTURE SAYS HAVANA STUDIOS, ALSO I WAS BORN IN A HOSPITAL 1958 HOWEVER THE HOSPITAL WAS DAMAGED IN A HURRICANE AND DID NOT OPEN UP AGAIN UNTIL 1959 BOTH PARENTS ARE DECEASED AND GRANDPARENTS ARE DECEASED WHICH WILL BE THE BEST TEST. OH NO KNOW SISTERS OR BROTHERS.
MyHeritage shows cousin matches as part of your DNA purchase for free and has some really wonderful tools to connect your research to your DNA matches. Using smart matching features to see how your tree is connected to others, and adding records you discover this way, may cost an additional monthly fee however. Still, MyHeritage is generally less expensive than Ancestry. You can also try their record collections for free here.

Both men and women can take mitochondrial DNA tests (because we all possess mitochondria in our cells), but it’s worth noting that women are unable to take Y DNA tests as they do not possess a Y chromosome. If you’re female and you’d like to learn more about your paternal lineage, you can ask a close male relative to take a Y DNA test on your behalf – read our article about Y DNA testing for more information.
For these reasons, mapping segments of your autosomal DNA to whole continents can be determined with a high level of certainty, but when you try to attribute these segments to specific tribes, regions or even countries, the certainty decreases. This is why some genetic ancestry companies will attribute a proportion of your DNA to areas such as ‘Eastern Europe’ or ‘Southern Asia’, instead of to specific countries.
Every human carries two copies of the genetic code, one inherited from the mother and one from the father, some 6 billion letters in all. Apart from identical twins, no two individuals have the same genetic code.  With the exception of the egg and sperm cells, all the cells of our bodies have 23 pairs of chromosomes, 46 in all. One chromosome of the pair is inherited from the father and one from the mother. However, in males the 23rd pair consists of a so-called Y-chromosome and an X-chromosome, whereas females have two X-chromosomes.  The Y chromosome contains a gene which triggers embryonic development as a male and carries information about the male’s paternal lineage.
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