Do you only need to take one DNA test?

If you're wondering how many DNA tests you should take, wait no longer.


While the question sounds really simple, there are some complexities to how many DNA tests a person should take.


What type of home DNA testing kit should you take?


The most common home genetic genealogy test explores your autosomal DNA.


Autosomal DNA looks at your entire genome, all 23 pairs of chromosomes. In many cases, it looks at SNPs on each one to then match up with other people. This test may only help you match relatives who share a common ancestor back to your 5th great-grandparents. Both males and females can take this test.


The next that people are most familiar with is the Y-DNA test, the first commercially available kit. Y-DNA testing looks at the male's y sex chromosome. This test looks at certain sections of that chromosome and the differences that they may have with others. Only males may take this test.


A mitochondrial DNA test examines the genetic material outside your cell's nucleus, which each proceeding generation inherits from their mother. Both males and females can take this test.


SNP-specific genetic tests are used for certain medical procedures and diagnostics. Others look for specific y-haplogroups.



Which Genetic Test is the most accurate?


The most accurate DNA test is the one that answers your question. Putting aside ethnicity results, which aren't always what you think, let's explore the four types listed above.


Autosomal DNA testing may be accurate to your 5th great-grandparents. However, if you share DNA less than 7 centimorgans with someone, this might be a false match. Additionally, with endogamous populations, your may share enough centimorgans with another test taker that they appear to be more closely related to you than what is genealogically accurate. Therefore, you should always combine autosomal DNA testing with genealogical research to validate your relationships.


y-DNA and mt-DNA are accurate in determining your haplogroups who else share that segment of DNA. However, identifying your common ancestor between you and your match becomes difficult as the link may happen before paper genealogy trails begin.


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Which Type of Genetic Test Should You Take?


If your question is is, "do I need one of the above tests?"


My return question is, what is your genealogy research question? Or rather, what are you trying to find out?


Each one of these tests serves a different purpose.

  • Y-DNA researches only the patrilineal line, or father's father's father, etc. This test may find that males find a shared male common ancestor with another person hundreds of years ago.

  • Mitochondrial DNA explores only the matrilineal line, mother's mother's, mother's, mother, etc. This test may find that anyone shares a female common ancestor with another person hundreds of years ago.

  • Autosomal DNA looks at all branches of your family tree. But shared DNA matches have common ancestors primarily back only six generations.

  • SNP-specific tests typically explore genetic issues.


Once you know what you want to learn, you can determine whether you need one or more than one test.


Should You Test with Multiple DNA Companies?


Ancestry 23andMe, MyHeritage, Family Tree DNA, and Living DNA offer home genetic tests. Thus, your next question might be whether you should take autosomal tests with the different companies that offer these?


While it's common to assume that an autosomal test will offer the same results, each company is actually looking at slightly different DNA segments. Thus, the ethnicity estimates are different, sometimes wildly different, across the companies.


Additionally, your DNA matches may differ not only because not everyone is in the same database but because you don't match the segments each DNA company examines.


In this video, I use a whiteboard to help you see how testing at different DNA companies may or may not give you the results you need to answer your research question.


Watch this video now.


Video: Why should you test with all DNA companies


In short, you can see that if you test at one company, such as MyHeritage, you may find three DNA matches. But by not testing at Ancestry as well, you might miss out on finding three additional genetic relatives who might be more closely related.


The biggest problem in genetic genealogy is we don't know where our genetic relatives have tested before we take our test.


As such, if you're only taking DNA tests for the fun of it, take only one test but don't the ethnicity results won't likely tell you the accurate picture of your family history.


If you are trying to break through genealogy brick walls, test with Ancestry, MyHeritage, 23andMe, Family Tree DNA, and Living DNA. There are some money-saving ways to have your DNA in each database without paying for five DNA tests. I discuss that in my book: DNA Q&A: Real Questions for Real People about Genetic Genealogy.



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