DNA Print Test Accuracy

[Rasfarengi]

Autosomal AncestryByDNA Ancestral Origin™ Population Assessment


Are these DNA"print" test accurate? I'm thinking about getting one, but I'm not sure if it is worth the effort.

[dentate]

The DNA print test is s intended to tell you whether you have ancestry from a particular ethnic group and approximately how much. It does this by looking at specific genes and alleles of genes that are typically associated with particular populations, though not necessarily restricted only to those populations. It then bases a "percentage" ancestry on how many markers and of which kind they find in your autosomal DNA.

This is full of problems, though. It does not tell you from which parent or grandparent you inherited that ethnicity. It also makes many other assumptions about how your ancestor's genes are inherited. Autosomal genes recombine. If they didn't, we would all get half our genes from one of Mom's two parents, the other half from one of Dad's two parents--plus Dad's Y chromosome--and the other two grandparents would contribute nothing. While everyone gets 50% of their genes from one parent and 50% from the other (except the mtDNA and Y DNA of course), because of recombination the genes you get from each parent are a mix of Grandma's and Grandpa's contributions. The contributions don't have to be equal, though; some genes mix and match more than others.

So the DNA print test makes some assumptions, such as that all the genes it uses to "mark" or identify ethnicity are equally likely to recombine, that a specific marker signifies only a particular ethnic group, etc. In small populations, if you go back not too far into the past you will find that one person is likely to be your ancestor in more than one line of descent, so not all "contributors" get equal representation. I'd say that the DNA print is an interesting suggestion about what may be in your past but that numbers like 52% and 59% are very rough estimates and need to be taken with a large grain of salt.

mtDNA and Y DNA avoid all these complications, but they also have their limitations. Using both mtDNA and Y DNA for analyis you learn about exactly two people of all the hundreds who were your ancestors at a particular time. I, for example, have J2 and N1b haplogroups, both typical Ashkenazi, but (like the Lemba) I could have every other line of descent 100% Bantu and still see the same thing on my FTDNA page. That isn't likely, of course, because the Y and mtDNA are "tracers" that mark populations--where your mtDNA or Y DNA came from, you likely have many other contributors from the same group--but the more relatives you test, the better. For example, my mother's brother is haplogroup P. That's supposedly Central Asia. This tells me that I have one line of descent from there, and I would have to assume that the community to which that line of descent belonged and in which marriages took place had others of the same origin...so the best way to really know where you came from is to test more relatives.

I better stop now, before the DNAPrint people get mad at me.

[Rasfarengi]

what places do DNA print? Does Familytree DNA?

[T E Peterman]

"mtDNA and Y DNA avoid all these complications, but they also have their limitations. Using both mtDNA and Y DNA for analyis you learn about exactly two people of all the hundreds who were your ancestors at a particular time."

There a way of getting around that. Test carefully selected relatives whose patrilines & matrilines are derived from the internal part of your pedigree (eg, my father's myDNA; my maternal uncle's y-DNA). If you know a lot about your more distant cousins & have the cash on hand (or great persuasive powers), you can get results for many of the internal lineages.

Timothy Peterman