Here’s a neat article I found in my Feedly posts today. Click “Imagination Station” for a simple explanation of the DNA extraction process. They’re using strawberries in the video, but, as you’ll see, you could try it on just about any living matter…including yourself.
The problem, of course, is other than having a dish of cloudy material as in the video, actually seeing the DNA you extract is a completely different story!
Have you done any DNA testing? Three major companies are in the DNA business: FamilyTreeDNA, 23andMe and AncestryDNA. Which test you take will be driven by the purpose of taking the test in the first place. The short story is this: The most popular test today is the Autosomal DNA test or atDNA test. All three companies do this test. Keep in mind that there are 23 chromosomes in every nucleus of every cell in your body. One of those chromosomes is the sex chromosome which is either X-X or X-Y. This chromosome determines whether your are female (X-X) or males (X-Y).That leaves 22 that are made up of a recombination of the DNA from your father (roughly 50%) and your mother (roughly 50%). It’s the recombination process that determines which of your father’s traits you will inherit and which of your mother’s. That’s also why siblings can either vary a great deal in their appearance or, if their appearances seem quite similar, one may have red hair and the other brown.
Logically, if you’ve got 50% of your mother’s atDNA and she received 50% from each of her parents, you can only have 25% from each of her parents. The same holds true with your father’s atDNA and that what makes up the 50% you inherited from him, 25% of which is from his father and 25% from his mother. The farther back you go up your family tree while applying the fact that the 50% gets halved at each generation. You’ll have 12.5% from each of your 8 great-grandparents, 6.75% from each of your 16 2nd great-grandparents. Then take into account the billions of possible ways that each recombination can produce, it gets a little tricky to go very far beyond 5 or 6 generations. We refer to it as a “cousin finder.” Ethnicity can be inferred to some degree and in broad generalities: Northern European, Sub-Saharan African, Ashkenazi Jew and so forth.
The second and third types of tests will take you deep into the genetic histories of your direct maternal or paternal lines. Only men have and thus can pass along Y-DNA. A man gets his from his father who got his from his father and so on. So to trace a paternal line, the Y test is quite useful for 2 reasons. It’s biologically impossible to get a Y chromosome from a male ancestor other than from your direct line. And it mutates at a very slow rate meaning that it stays relatively intact for thousands of years, unlike atDNA which “melts” in each generation.
The third test is for mitochondrial DNA, the mother’s unique contribution to the equation. Unlike the Y, mitochondrial or mtDNA is in everyone’s cells. For the lack of a more scientific answer, it is what powers the cells, allowing them to live, divide and recombine so that life can go on. But, only the mother passes the mtDNA even though both she and the father have it.
Here’s the reason. Mom has her Mom’s mtDNA and Dad has his Mom’s mtDNA. At the point of conception, the ovum contains mom’s mtDNA as she supplied the ovum containing it. Dad supplied the sperm but the mtDNA is in the tail. Picture your science books where the sperm wiggles its way to its destination. At the moment of conception, the tail falls off and thus the mtDNA from the father is no longer a factor. It’s a lot like a space rocket. Once the rocket clears earth’s atmosphere, the boosters fall away. They’ve done their job!
The mtDNA will take you backwards to your mother, her mother and her mother’s mother and so on.
Both Y and mtDNA can give you reasonably accurate description of your genetic background. But it is important to say that as far as family research is concerned, DNA tests do not replace standard research practices. It will only help to prove or disprove what you’ve discovered.
For a more detailed explanation of DNA and the various types and tests, there are some excellent bloggers whose backgrounds in the science is much deeper than my own:
- www.dnaexpain.com by Roberta Estes
- www.legalgenealogist.com by Judy G Russell
- www.thegeneticgenealogist.com by Blaine Bettinger
That should be more than enough to get you started! Good luck!
Visit Old Bones Genealogy of New England at www.oldbones.info