Are DNA ancestry tests really reliable? I am looking to get one....?

Let me explain what you will be buying.

You have 46 chromosomes. Two of your chromosomes are sex chromosomes. If you are a male you got Y from your father and X from your mother. If you are a female, you normally got X from both parents.

The other 44 chromosomes are your Autosomal DNA, 22 from each parent. You got it 50-50 from each parent but not normally 25% from each of your 4 grandparents. The reason why there usually will be some bias in what you inherited from grandmother and grandfather on both sides of the family. This is because of "meiosis." This means you and your siblings could have inherited anywhere from 0 to 50% from any one grandparent. The gap usually isn't that big but can be. How you inherited any bias will not be how your siblings inherited it unless you have an identical twin.

Mitochondrial is not a chromosome but in the cytoplasm (connective tissues) outside your cells. Both males and females get Mitochondrial from their mother only. Naturally only the daughters pass it to the next generation.

X can be a little different. If you are a male you got X from your mother but she got X from both parents. Whose X did you get, your maternal grandmother's or your maternal grandfather's. It can differ among brothers who share the same mother. For females the X she gets from her mother is in the direct maternal line like Mitochondrial. The X she gets from her father comes from her paternal grandmother. Then the question is whose X did her paternal grandmother pass on to her father. Therefore the X a female gets from her father can be from her great grandfather or her great grandmother.

For the overall testing they use Autosomal along with the X. There are no Haplogroups with this type of testing. Due to the differences in how you inherited Autosomal from your grandparents and the X, the results of this type of testing will usually not be exact among siblings even if they are tested by the same company at the same time. You just didn't inherit it the same.

Also if you are tested by more than one company, the results will not be exact as the only thing companies can do is match you with population groups in their database. They each have their own database. So if one doesn't have or is deficient in certain population groups another has and vice versa naturally there can be differences. It has also been reported if you are tested by a company and go back to the same company sometime later, by that time they have obtained more population groups that can change your picture.

Now for years companies have done Y & Mitochondrial testing and the results are respected as being very precise With each they will assign a person to a Haplogroup and show them the origin of their ancestor going pretty far back. The only thing, if you are a male you got each from only one person in each generation you go back. If you are a female you normally only got Mitochondrial from only one person in each generation you go back. Your ancestry doubles each generation. Example: By the time you got back to your 32 great great great grandparents and if you had both tested, 30 of them will not be included in either results. For females who normally can only have Mitochondrial tested, 31 of them will be excluded from the results.

So which is the best company to use for the overall testing. It is the one that has the population groups that best match your ancestry and there is no way we or even you can know that.

The 3 most recommended are

FamilyTreeDNA which is the oldest in genealogy testing and has the largest database. I understand they do the testing for National Geographic.

23andme. In addition they will give you a report on anomalies you have in your DNA that can present a health risk for you or one of your descendants. I found out about 55 years ago I had the allele for Tay Sachs. If I had the condition I would have died before my 5th birthday. I am 81. However, if I had produced children by someone who also had the allele for Tay Sachs, our chances of having a child with the condition was very high.

Ancestry.Com

The real value of genealogy DNA testing whether Y & Mitochondrial or Autosomal along with the X is if you are into traditional genealogy work using documents records and the company you choose has cousins of yours going back several generations that they have tested and they notify you of those cousins and you make contact with them and they are also into traditional genealogy work, you can make contact with them and collaborate information. They might have discovered ancestors you haven't and you might have discovered ancestors they haven't. For this reason if I had the money, I would have all the companies do mine.

Edit: They normally don't give specific nationalities as really there aren't any pure nationalities or ethnicities. Spanish and Portuguese usually is listed as Iberian.

You already know what "race" you are........... as far as ancestryDNA tests they are for entertainment purposes only get 6 tests done and you will get 6 different 'results', so all they do is entertain you they do not tell you who your ancestors were or where they came from, the only way to know that is to research real records prove

I think they are reliable. I mean, you got two situations going on. Possibly more, to understand. The test itself, and the population samples it relies on to generate your results. You also have to consider genetic recombination factors as well, which means, in laymens terms, that depending on the combination of DNA you inherited from each parent, can dramatically affect what will show up on your DNA test, and then that situation goes back indefinitely. So, technically speaking, you might not inherit any DNA from a particular great grandparent, unless it was a direct maternal ancestor, or if you are a male a direct paternal ancestor (since they always inherit Y-DNA, and women and men will inherit their maternal MtDNA). But let's say your Great grandparent was Irish, and all your other Great grandparents were Spanish. Since you inherit exactly half your DNA from each parent, and it totally random what 50% you inherit, although your grandparent would be half Irish, it's possible for your parent to only inherit the half that was not Irish, although that would be really unusual, but even if they inherited only like 10%, so it is now even less likely for your random DNA you inherited to have gobbled up some of that smaller percentage. Ok, now that I explained that, back to the test itself. Each testing company only tests some of your SNP's. Not all of them. That would be insanely expensive and time consuming. So to make these tests more cost effective for the general public to want to purchase them, they have worked with scientists who have been able to narrow down certain SNP's that are more likely to show "unique" genetic markers, that are commonly found in certain autosomal haplogroups of various heritages. Like, say the red hair gene or something. Like that might be one that they know to make sure their test would check for, etc. So there also is a bunch of other genes, that may not be as illustrative of a certain heritage, and so the percentages they give you for your chunks of heritages are always a range estimate, because it accounts for all the SNP's they didn't look at, and how the whole picture if fully tested could be much higher or much lower. You also have to consider the genetic populations that they used to establish a baseline for that particular heritage. Although they claim they vetted them, and made sure that they went back like 4 generations or something, there is always room for error in that, if say there is a random different heritage person one more generation back that they inherited a bunch of their DNA through DNA random gene recombination. This problem, however, is not as much of a problem, in that, you can upload your DNA results to other programs, that have different calculators, so can kind of cross-check the results to see if they come out pretty much the same, and I did that. Like on Gedmatch, which showed similar results, and Gedmatch has a whole bunch of calculators, which some are better than others, depending on what heritage you are. Like, for Europeans, it's often best to use the "Eurogenes" calculator, and people with more Middle Eastern, or Asian, etc., may want to use Dodecad, for example.

In summary, I thought it was super cool, and there were definitely some surprises, and speaking of the recombination issues, since both my parents took the test, I was able to see what I inherited from each parent pretty well. In fact, opposite issue happened. My mom had 9% Irish and my dad 12%, and I got 21%. In other words, I gobbled up all of each of my parents' Irish genes, and so apparently I am more Irish than both my parents, but it's not like you can say, this is super definitive. But is very interesting, and it does give you a lot of information, that for the most part, I think is accurate, but there is always room for some error.