Genealogical DNA Testing

DNA evidence has allowed me to break though major brick walls that had stymed me for decades! It's a fantastic tool. I just wish it had been available a few years earlier so I could have had my grandmother's and father's DNA sampled.

Get the oldest members of your family tested NOW!

What is DNA all about, anyway?

At the base level, our genes, the genetic code for how our cells and our body work, is encoded in our DNA. People have 46 chromosomes in their DNA, 23 from each of their parents. The chromosomes are grouped into pairs, so each of their 23 pairs is half from their mothers, half from their fathers. Their siblings also each get 23 from each parent, but their's will be a different set of 23. (Unless they are identical twins.)

22 of these chromosomes are called Autosomes. They change with every generation. A person always gets half their DNA from their parent. But while each parento got half of theirs from their parents, it isn't evenly passed on. The DNA they received from one of their parents is passed on at random, which means a person could get anywhere from 50% to none from each of their grandparent.

Autosomal DNA testing allows one to compare how many large segments of DNA, called SNPs you share with others. The more you share, the more closely the match is related. This is where I find DNA testing to be invaluable.

Most testing companies also compare your DNA test results with those of known ethnic populations. This is interesting, but not terribly useful in genealogy.

The 23rd chromosome pair is the one that determines gender. People alway get one X chromosome from their mother, who has two. Men only have one X which is paired with a Y chromosome. If the father's contribution was his X chromosome, the child is female. If they got his Y chromsome instead, they are male. Men always receive their Y chromosome from their father, who received it from his father, and so on.

Our cells also have mitrochodia within them, which also have their own DNA. This is abbreviated to mtDNA. People always inheirit their mitrochondria, and the included mitrochondial DNA, from their mother. Their mother recived hers from her mother, and so on.

Because the source of the Y chromosome and mitrochondial DNA is known, one can track back. And since they aren't recreated and remixed at every generation, they are relatively stable. Since the rate of chage, or mutation is also known, there is some ability to predict how far back two people have a common ancestor.

There are three types of DNA tests:

• Autosomal DNA tests reflect the DNA contributed by all ancestors, but, at best, only show results from the previous 8 or 9 generations.
• Y-DNA tests only trace DNA back through the patrilineal ancestry, but results go back for over 100 generations.
• mtDNA tests only trace DNA back through the matrilineal line, but results go back for over 100 generations.

This diagram illustrates which ancestors will show up within the results for each type of test. Autosomal results are only meaningful for about 8 generations, but are pertinanlt for all your ancestors within that range. Results from the other two test types go way back, but only involve two lines.

I find the autosomal test to be the most useful to genealogical purposes. DNA test results have allowed me to prove connections where the paper trail alone is inconclusive and it has guided me to the locations where I could find the paper documentation I needed.

Visit The DNA Geek's site for more information to help you choose which test(s) would be best for you.

Genealogical DNA Testing Companies

AncestryDNA

Tests Autosomal only. Matchs against 22+ million other people.

23andMe

Tests Autosomal, Y-DNA & mtDNA. Matchs against 12+ million other people.

MyHeritage DNA *

Tests Autosomal only. Matchs against 5+ million other people. Relativly more concentration on Europe.

FamilyTreeDNA *

Tests Autosomal only. Matchs against 1.7+ million other people.

LivingDNA *

Test Autosomal only. Concentration on British Isles, matchs against 300,000+ other people.

African Ancestry

Tests Y-DNA & mtDNA only. Concentration on Africa.

Companies marked with an * allow DNA from other testing companies to be uploaded to their databases. Putting your DNA data on additional sites increases the odds of finding that match to a distand cousin that you need to break through a wall.

Many of the items in the tools and widgets links are related to DNA analysis.