GENETIC DNA TESTING

In the last 20 years or so geneticists have learned to study our ancestry through our DNA. DNA is the molecule that encodes the genetic instructions for building and operating all living things. DNA is a double helix that looks like a twisted ladder. Each rung on the ladder is made up of a pair of chemicals. There are only four of these chemicals and they pair up together two by two. Differences in DNA occur in the sequence of these pairs. Humans are 99.9% genetically identical meaning all the rungs on the ladder are the same. All the differences we see in the way people look, what diseases they may be prone to etc. come from the .1% difference. That doesn't seem like much until you realize that there are about THREE BILLION base pairs in which those differences may be expressed. Geneticists have found that they can track the ancestry of someone by comparing a few hundred of these pairs.

The idea is fairly simple. The first people that mutated into humans in East Africa are called Adam and Eve and we all descend from them (there are scientific papers devoted to proving that all human DNA came from one set of individuals but I do not understand how). The DNA from these people was handed down identically to their children, and then to their children, etc. But, every few thousand years a mutation occurs. This is usually just a change in the sequence of a rung on the ladder somewhere and is usually inconsequential. It may cause a change of hair color or a bigger nose, or possibly nothing at all. The mutation is then handed down to all of that person’s descendants. So, by looking at the differences, or similarities in mutations, we can tell approximately who we are related to and by how much. Also, they can tell by the concentration in mutations from what areas the family came. They have also gone back and tested the DNA in a lot of very old people who have been mummified or discovered frozen in ice, etc. to track the migration of these different DNA mutations.

National Geographic has begun a world-wide project called the Genographic Project. They are testing thousands of people worldwide to create a map of the migration of the human race. https://genographic.nationalgeographic.com/human-journey/ 

So the big question for me is how do I, and my family fit into all this? Thus begins my DNA genealogy search.

There are basically three different DNA tests that you can have done. 

The Y-chromosome test (Y-DNA) is one that only males can do since females do not have the Y-chromosome. Without mutations my Y-DNA would be exactly like Adam’s. But the mutations along the way have distinguished the line into an ancestral tree. So if my Y-DNA is identical to another individual’s Y-DNA you can reasonably say that we share a common ancestor somewhere in the relatively close past (i.e. we are on the same branch of the tree). If we are identical in all but one spot on the Y-DNA then the common ancestor is probably further back but still close genealogically speaking (i.e. we are on branches next to each other), etc.

The mitochondrial DNA (mtDNA) tests the DNA that is handed down through females and can track all the way back to Eve, with the mutations also showing the migrations through the ancestral tree. Both males and females can have the mtDNA test as a male inherits his mother’s mtDNA but does not pass it along to his children.

The autosomal DNA (atDNA) test looks at the combination of the entire DNA from both parents. Since this is a completely random recombination of each parents DNA for each child, (this is why siblings look similar but also different). This test is used primarily to identify relatives you can find to share genealogy studies with. With all of the recombining going on through the generations the atDNA test is only good for about four to six generations back.