Prior to Mendel’s research with pea plants in the mid-1800s, it was assumed by everyone that offspring were a blend of their parents’ traits. Mendel found that this assumption was false. Purebred tall pea plants crossed with purebred short pea plants did not produce medium-sized offspring. They produced tall offspring. Traits did not blend. The world changed! NOT! No one even paid any attention for about 50 years. And then, it was only a few scientists (who became geneticists) who really noticed.
To understand this better, let’s start with a simple Mendelian (single gene trait) example: ABO blood type. You get half of your chromosomes (23) from your mom and half (23) from your dad. Both sets of chromosomes have the same genes, BUT they may have different forms of those genes. In our example, your chromosome #9 from your mom contains the ABO blood type form O. The one from your dad is A. Your blood type is not a blend of O and A. It is A (because A is dominant over O). But your genotype is AO. Now, it is years later and you are ready to have a child. Your mate is blood type O. That means your mate has a genotype of OO. Due to the randomness of meiosis (cell division that produces gametes: eggs or sperm), your gamete contains the O form from your mom. Your mate also provides an O, so your child will have blood type O and genotype OO. Not only is your dad’s gene for ABO not passed on to his grandchild child, neither are any of the nearby genes on that chromosome. And if your dad’s chromosome #9 did not undergo recombination during meiosis (exchanging material with the other chromosome #9s), all your dad’s genes on that chromosome are absent from his grandchild child. It is possible, although improbable, that your child contains chromosomes and genes ONLY from your mother. It is also possible, although improbable, that the only chromosome your child inherited from grandma is #9. There is no blending of the grandparents’ traits in the grandchild.
What this means is that in only two generations, traits can be lost from a family line. In our example, you know who your parents are, but it is possible that the traits of one of your parents will not be evident in your child, which is your parent’s grandchild. The big point? Genetics and Genealogy do not match.
Maybe you are really into genealogy and have a family tree dating back a couple of hundred years. You know who your ancestors are. But you decide it would be cool to have genetic testing done too. SHOCK!! According to the genetic testing, you do not have any Native American ancestry. But you know that your mom’s grandmother was Sioux. You have a picture of her! What gives?!
What gives is that since genes don’t blend, they can be lost to subsequent generations. Also, current genetic testing is only able to look at a subset of all your genes. Maybe your maternal grandma’s genes that you did inherit aren’t in that tested subset. Who knows?
Genetic information provides additional insights to your ancestry, but is not a substitute for genealogy. You need both types of information to fully understand your personal past.
Takeaway message: If you read an article, or see a show that states, “Based on genetic testing, there is no evidence that Population A is in the ancestry of Population B” remember that not all genes get passed down to all descendants, and that genetic testing only examines a subset of genes. Contrary to what that genetic test showed, it is quite possible that Population A is indeed in the ancestry of Population B. Genetics and Genealogy are different, complementary ways of knowing the past.
What this means is that in only two generations, traits can be lost from a family line. In our example, you know who your parents are, but it is possible that the traits of one of your parents will not be evident in your child, which is your parent’s grandchild. The big point? Genetics and Genealogy do not match.
Maybe you are really into genealogy and have a family tree dating back a couple of hundred years. You know who your ancestors are. But you decide it would be cool to have genetic testing done too. SHOCK!! According to the genetic testing, you do not have any Native American ancestry. But you know that your mom’s grandmother was Sioux. You have a picture of her! What gives?!
What gives is that since genes don’t blend, they can be lost to subsequent generations. Also, current genetic testing is only able to look at a subset of all your genes. Maybe your maternal grandma’s genes that you did inherit aren’t in that tested subset. Who knows?
Genetic information provides additional insights to your ancestry, but is not a substitute for genealogy. You need both types of information to fully understand your personal past.
Takeaway message: If you read an article, or see a show that states, “Based on genetic testing, there is no evidence that Population A is in the ancestry of Population B” remember that not all genes get passed down to all descendants, and that genetic testing only examines a subset of genes. Contrary to what that genetic test showed, it is quite possible that Population A is indeed in the ancestry of Population B. Genetics and Genealogy are different, complementary ways of knowing the past.
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