Upper level 'Chateau de Dieppe', France, built 14th century. Image by Francis Fortin.
Upper level 'Chateau de Dieppe', France, built 14th century. Image by Francis Fortin.
| Introduction | Types of Tests | Triangulation | Who should Test | Submit a Sample | Surname Projects | Questions on DNA | References |
Introduction to DNA Research [top]
There are two basic types of genealogy research:
1. Your 'paper pedigree', compiled by a researcher to trace your ancestry back beyond the road blocks, with all the proper recorded citations and sources. Unfortunately, the accuracy of all this work is not infallible, since errors may creep into it.
2. Your DNA makes you who you are, it has no errors, so it is the real 'you'. If you are fortunate, both your paper pedigree and your DNA research might match each other.
Types of DNA Tests [top]
There are three principle DNA tests for use in genealogy research. Since technology is constantly advancing and additional tests are now available, consult the literature of the test kit vendor for details. For a more detailed explanation of the DNA tests, please see "Understanding the Different DNA Tests", by Fran Tivey (Je Me Souviens journal, issue 2018-2, p. 18). If you have more questions about DNA Research and which test is right for you, please see the Questions section below.
1. Autosomal (atDNA) testing can find matches in ANY branch of your family tree. The atDNA test is good for finding relations within 5 or 6 generations and both men and women can take it. Close relations share large segments of DNA. More distant relations share smaller segments of DNA.
2. yDNA testing analyzes the Y chromosome that is passed virtually unchanged for generations from father to son. The test, which can be taken only by men, examines just one branch of a family tree: the male line, being a father's father's father, and so on.
3. mtDNA testing looks at mitochondrial DNA, a certain form that is passed from a mother to all her children. Both men and women can take the test, which aims to trace ancestors on a mother's side. But the test follows only the direct female line, meaning a mother's mother's mother, and so on.
All three tests are used to determine if people are related, even through people who lived 500 years ago, or perhaps determine the country of their ancestors. No single test can look at the DNA of a father's mother, or of a mother's father.
If you go back just 10 generations (about 300 years), you will have 1,024 ancestors in that 10th generation. According to Henry T. Greely, director of the Center for Law and the Biosciences at Stanford University, DNA testing yields a relatively narrow view of your complete heritage. That's because the yDNA test tells you about only one male ancestor in the 10th generation, the mtDNA test tells you about only one female ancestor in the 10th generation, and the Autosomal test is most reliable for about 5 generations.
What is Triangulation? [top]
There are two kinds of triangulation that are used in genetic genealogy:
1) One for the Y chromosome (yDNA) and it’s to determine the original values of the DNA of the common ancestor.
2) The other type is for autosomal DNA and it’s to determine if you share a common ancestor with someone and what the DNA of that ancestor looked like.
Triangulation through yDNA can be used to confirm the accuracy of your paper pedigree. For example; if your paper pedigree traces your male line back to an ancestor that is in common with someone elses pedigree, AND your yDNA is a close match to the yDNA of the other person, it is a pretty good indication that your paper pedigree is accurate back to the common male ancestor. However, it does not prove that all of your paper pedigree is accurate, just the male ancestral line.
Who should get tested? [top]
You can test yourself simply enough. But if your parents (or grandparents) are living, you may want to test them as well.
Here's why: By testing someone that is one generation older, you will probably get more useful matches. Your 4th cousin is closer to a 3rd cousin to your parent and would be more likely to show up as a match for your parent.
When you test yourself, you get matches from both sides of your family. For more distant cousins it may be difficult or impossible to tell which side of your family the match is from. If you test your parents separately, you can confidently place unique matches on one side of your family. That allows you to focus your paper trail research on the correct side and eliminate half the work.
