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Once upon a time, there was a lone family historian who meticulously wrote down all he knew about "the family" in his notebook. Then came the typewriter, and with it came the filing cabinet.
From there we progressed to the personal computer - out with the filing cabinet, and in with the floppies.
Then someone invented the internet - no, we're not calling names here - and all of a sudden we find ourselves connected to the whole world.
And now, genealogy and science have come together and a new word was born: Genetealogy (genealogy + genetics)
Scientists aren't just helping us out of the goodness of their heart: They're trying to figure out the origins of men, while we try to find the men between us and those origins. Scientists need our DNA for this purpose, and we need them to show us which men followed which path leading them to where we are now.
Why the Y
Scientists have discovered that the DNA in the y-chromosome, found only in males, is passed from father to son, virtually unchanged, except for rare (and random) mutations. By testing these chromosome segments, it is possible to determine if two or more living males are related, and approximately when they had a common ancestor. The y-chromosome follows the straight paternal line:
This is the reason DNA surname projects only request male participants. Only the y-chromosome travels the paternal (surname) line.
Females on the other hand have mitochondrial DNA (mtDNA). mtDNA is in some ways a paralel to the y-chromosome. Just as the y-chromosome follows the straight paternal line, mtDNA follows the straight maternal line. mtDNA is passed from a mother to her son, but the son cannot pass it on to his offspring:
Thus, when we put it all together:
How DNA Testing Helps - Genetealogy
It can help you validate or invalidate genealogical records.
If you think you may have a surname spelling change or adoption in your line it can help you link to a common ancestor.
It can help you verify relationships with a family from a region where you believe your line may have lived.
It can help you find new relatives.
It can help you find those ancestors for whom there are no written records through DNA Matching.
Proving Relationships, one of the most useful aspects of DNA testing for genealogists. If you have a theory that two people might be related in your pedigree, but you have been unable to locate any documentation to prove your theory, DNA testing might be able to help. If the correct two (or more) people have their DNA analyzed, a signature match will indicate that they are closely related. A mismatch will confirm the two people are not closely related. Exact matches of Y-chromosome 25-marker tests will indicate that the two people are related within about seven generations. If one or two markers on the signature are different, the two people are still related but the relationship is more distant. A statistical model is used to determine the most likely number of generations between the two people.
Exact matches of Mitochondrial DNA sequencing also indicate relatedness, but there are not sufficient studies to determine the number of generations separating the two people.
Surname/Clan Reconstruction & Regional Migration, another common use of Y-chromosome tests (Y-chromosome Haplotype). Groups of families with a common or similar surname origin might want to know if (and how) they are related to one another. Individuals and groups can also discover genetic connections to others living in a country where the family is thought to have lived within a migration path.
What DNA Testing Will Not Tell You
These tests will not reveal any information about your health or your predisposition for certain diseases. These tests do not look at the regions of your DNA that are associated with health information or genetic traits. Since the regions being examined are between your genes, regions called "Junk DNA," nothing in the results will imply any health-related information.
These tests do not create a unique personal genetic fingerprint that can be used to identify you. Since you and other family members will have exact matching results, these tests are not capable of proving unique identity. You can think of these tests as a unique family fingerprint.
These tests do not tell you which ethnic tribe you may belong to or the exact country of origin for your surname. They are designed, rather, to allow you to discover these genealogical answers by comparing to others who are proven to fall within certain genealogical characteristics.
DNA Quick Facts