Testing, Testing - Turn this Thing On!
If you're reading this, you have probably seen those commercials on TV about the home DNA tests - "learn your ethnic origins". As evidenced by AncestryDNA sales recently eclipsing 10 million kits, interest in learning "where do I come from?" has exploded, while technology offers powerful new tools to help answer that question. So what is DNA testing, how does it work, and why should I do it? Great questions!
You have 23 pairs of chromosomes - 22 pairs of autosomes, and the 23rd is a pair of gender (XY) chromosomes. Chromosomes are made up of genes, which in turn are made up of DNA, which is the molecular basis of heredity - the traits we inherit from our parents, and they from theirs, etc.. All of your genes collectively make up your genome. For humans about 99.9% of our DNA is identical, yet this still leaves some 3 million differences between your genome and any other human. (For comparison sake, we appear to share about 96% of DNA with our closest cousin the chimpanzee.)
Four kinds of DNA are useful in studying inheritance:
• Y chromosome, inherited only by sons from their fathers
• X chromosome, women inherit one from each parent, while males inherit an X from their mother and a Y from their father
• Mitochondrial DNA, passed from a mother to all of her children, but is only passed on by females
• Autosomal DNA
Autosomal DNA is the bulk of what we inherit, and what most of the common DNA tests evaluate. This fascinating 2-minute video demonstrates clearly and quickly how we use autosomal DNA in simple terms. Every one - male and female - inherits approximately 50% of their autosomal DNA from each parent. But that autosomal DNA gets fragmented and changed in each generation, so when one finds a common segment of DNA between two people, it likely originated in a common ancestor.
And while siblings also inherit 50% from each parent, they don't each get the same 50%. So there is a lot of value in testing them as well. In my family three siblings who are 3rd cousins once removed (3C1R) to my dad have helped validate different connections to our ancestral McKnight family.
Though like any science, genetic genealogy can be incredibly complex, any family historian can make great progress with a very basic level of understanding. When we do an autosomal DNA test at AncestryDNA, 23andMe, FamilyTreeDNA or some other company, the genealogist is most interested in Shared Matches; people who beyond a shadow of a doubt are genetically related to us.
Autosomal DNA is reliable typically over 5 to 7 generations, a range of perhaps 125 to 250 years distant. With enough work, it is possible to identify common segments on specific chromosomes common to various branches of our ancestral family. Some of those segments disappear in just a few generations, while others may persist for far longer.
And because of those limitations, the more of our elderly relatives that test, the farther back into our ancestry we may reach. When they are willing to join our efforts, thank them! But it's also important to respect their wishes if, after you've laid out the benefits for them, they still decline to test. DNA bullying is a real thing, and it's not cool. Ever.
If you are wondering, I generally recommend people choose the Ancestry DNA test, unless you are interested in all of the medical and health analysis included with 23andMe. Although Ancestry's analysis tools are primitive and often inadequate, their DNA database is simply too large to ignore if family history is your main interest. Testing with one of those two companies leaves you the most options. You can download your DNA data and then upload it for free at several other testing companies, including MyHeritage and FamilyTreeDNA (both of which also sell test kits) and the comprehensive research site GEDMatch. While your DNA is of course constant, the different proprietary algorithms used in analysis produce small variations between companies.
Ancestry and 23andMe are the two largest databases, but don't currently allow uploads from other test companies. So get the most from your investment by choosing one of those two, then uploading to the sites that allow it. Cast your "cousin-catching net" as widely as you can to make the most connections and perhaps break down some "brick walls" in your family history. Whether you spit in a tube or swab your cheek, you have an enormous amount of family history right inside your own body and readily available to help you better know "who am I?"
And about those ethnicity estimates everyone is talking about? More in the next post :).
NEXT UP: What Do These DNA Results Mean?....
You have 23 pairs of chromosomes - 22 pairs of autosomes, and the 23rd is a pair of gender (XY) chromosomes. Chromosomes are made up of genes, which in turn are made up of DNA, which is the molecular basis of heredity - the traits we inherit from our parents, and they from theirs, etc.. All of your genes collectively make up your genome. For humans about 99.9% of our DNA is identical, yet this still leaves some 3 million differences between your genome and any other human. (For comparison sake, we appear to share about 96% of DNA with our closest cousin the chimpanzee.)
Four kinds of DNA are useful in studying inheritance:
• Y chromosome, inherited only by sons from their fathers
• X chromosome, women inherit one from each parent, while males inherit an X from their mother and a Y from their father
• Mitochondrial DNA, passed from a mother to all of her children, but is only passed on by females
• Autosomal DNA
Autosomal DNA is the bulk of what we inherit, and what most of the common DNA tests evaluate. This fascinating 2-minute video demonstrates clearly and quickly how we use autosomal DNA in simple terms. Every one - male and female - inherits approximately 50% of their autosomal DNA from each parent. But that autosomal DNA gets fragmented and changed in each generation, so when one finds a common segment of DNA between two people, it likely originated in a common ancestor.
And while siblings also inherit 50% from each parent, they don't each get the same 50%. So there is a lot of value in testing them as well. In my family three siblings who are 3rd cousins once removed (3C1R) to my dad have helped validate different connections to our ancestral McKnight family.
Though like any science, genetic genealogy can be incredibly complex, any family historian can make great progress with a very basic level of understanding. When we do an autosomal DNA test at AncestryDNA, 23andMe, FamilyTreeDNA or some other company, the genealogist is most interested in Shared Matches; people who beyond a shadow of a doubt are genetically related to us.
Autosomal DNA is reliable typically over 5 to 7 generations, a range of perhaps 125 to 250 years distant. With enough work, it is possible to identify common segments on specific chromosomes common to various branches of our ancestral family. Some of those segments disappear in just a few generations, while others may persist for far longer.
And because of those limitations, the more of our elderly relatives that test, the farther back into our ancestry we may reach. When they are willing to join our efforts, thank them! But it's also important to respect their wishes if, after you've laid out the benefits for them, they still decline to test. DNA bullying is a real thing, and it's not cool. Ever.
If you are wondering, I generally recommend people choose the Ancestry DNA test, unless you are interested in all of the medical and health analysis included with 23andMe. Although Ancestry's analysis tools are primitive and often inadequate, their DNA database is simply too large to ignore if family history is your main interest. Testing with one of those two companies leaves you the most options. You can download your DNA data and then upload it for free at several other testing companies, including MyHeritage and FamilyTreeDNA (both of which also sell test kits) and the comprehensive research site GEDMatch. While your DNA is of course constant, the different proprietary algorithms used in analysis produce small variations between companies.
Ancestry and 23andMe are the two largest databases, but don't currently allow uploads from other test companies. So get the most from your investment by choosing one of those two, then uploading to the sites that allow it. Cast your "cousin-catching net" as widely as you can to make the most connections and perhaps break down some "brick walls" in your family history. Whether you spit in a tube or swab your cheek, you have an enormous amount of family history right inside your own body and readily available to help you better know "who am I?"
And about those ethnicity estimates everyone is talking about? More in the next post :).
NEXT UP: What Do These DNA Results Mean?....
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