The answer is very accurate…to about five or six generations. Beyond that, the benefits drop sharply, although a small percentage of matches with common ancestors as far back as ten generations can sometimes be detected.

Autosomal DNA is the type of DNA that is most commonly tested. When we talk about “DNA test results,” rarely does this mean anything other than autosomal testing. This is the DNA we all inherit from autosomal chromosomes. Autosomes are the numbered chromosomes (not including the sex chromosomes). We all have 22 pairs of autosomes, each pair representing genes inherited from Dad and genes inherited from Mom. We also all get a pair of sex chromosomes (the “X” and “Y.” More on that second one later). These chromosomes are numbered from largest to smallest. Chromosome One, for instance, has about 2,800 genes. Down at number 22, there are only around 750 genes.

Centimorgans are simply a unit of measure. When your DNA test results come in, you will not only be shown your “ethnicity estimates,” how much of your DNA came from what countries or racial backgrounds, but most importantly, who you share your DNA with, and how much DNA you share. Again, the more DNA you share, the closer the relationship. That shared DNA is always given in centimorgans. The symbol for centimorgans is “cM.” You don’t need to know anything more than that!

When it comes to DNA testing to discover your ancestors, it’s important for you to choose a testing company that will best help you achieve your goals. There are several of them out there. The best known ones are Ancestry.com, 23andMe, FamilyTreeDNA, and MyHeritage. Each is a leading citizen in the family history community. And each offers autosomal DNA testing, the most helpful type of DNA test available. Let’s look at each company:

FamilyTreeDNA was the first company to offer DNA testing to the public for family history. And while their “Family Finder” DNA offering is their staple offering today, they are also the only company to currently offer Y chromosome DNA testing. Y testing follows the male or “Y” chromosome back through the ages. They also offer mitochondrial testing, which follows the mother’s female line back through the generations. To achieve some research goals, these tests can be very helpful. Despite their early beginnings, “FTDNA,” as the company is often called, does not have nearly the number of autosomal test results in their database as the other companies.

23andMe has been at it for many years now, as well. They have a good size database… believed to be the second largest… yet many of those tested there have been more interested in examining health issues, meaning they have little interest in genealogical pursuit and rarely post their family trees, an important aide in determining relationships.

MyHeritage is a latecomer to DNA but has done a fabulous job of building a good size database, which includes many DNA testers from Europe, their principal territory, which can be very helpful if your research goals are focused there.

Ancestry is the most dominant company in DNA. It’s database is HUGE! At last count, over 18 MILLION people have tested at Ancestry.

Prices at all these companies are similar, ranging from sale prices around $49 a kit to full prices at $99.

My personal recommendation is always to start with Ancestry DNA. Ancestry’s monster database gives you more people to compare your DNA test results against than any other company by far. And, as mentioned,matching is the key to using DNA to help you identify ancestors.

Think of each of the test results in the Ancestry database as being like a lottery ticket as any one of them could be the key to solving your genealogical problem!If you look at the price of your kit in terms of “cost per match,” no one compares. It’s like getting many times more lottery tickets for the same money you would pay someone else!

Also, at present, you can take your Ancestry DNA test results and load them up to MyHeritage.com for FREE, making the kit even more cost efficient. You can also compare your Ancestry DNA results with the testers at FamilyTreeDNA for just $30. Plus, Ancestry has remarkable tools for organizing your DNA matches into ancestral categories and searching through your matches. And while some sites offer some important features that Ancestry does not, this is always my first recommendation to friends and family. (Full disclosure… Ancestry is a sponsor of Extreme Genes.)

Remember, however, that genetic genealogy goals aren’t always solved by matches at just onesite. You may have to drop your fishing lines in more than one “pond” to catch what you’re looking for.

It’s important to note that you can get a DNA kit from Ancestry.com without being a subscriber to the general site. This will provide you with your ethnicity report and a list of matches, close and distant. However, you will be unable to see the family trees of your matches, and that is an essential component of genetic genealogy! So if you decide Ancestry is the best place for you, plan on subscribing for at least a free trial period if not for a much longer paid period.

A couple of ways, actually. The first is through the ethnicity report. Most all companies will break down your results to give you a list of various regions or countries your ancestors lived in at some point. This report is also helpful in identifying various racial backgrounds such as Asian, African, Native American, European and Ashkenazi Jewish. Though interesting, this report is broad in scope and not necessarily useful in pointing to specific ancestors. It is, however, a great way for companies to introduce people to genealogy! The second way is what we’ll be most concerned with. And that is finding matches! When your DNA results come in you are likely to see the names of cousins you know and many more distant ones you don’t know. By determining the likely relationships of these people to you, see which matches they have in common with you, and by comparing their family trees with yours, you can frequently determine who the ancestor or ancestors are you have in common with them. Sometimes, these are ancestors not on your tree at present, but a generation or more back. And that’s how you grow your tree, or confirm the ancestors already on your tree! Plus, these cousin matches often have records, personal knowledge, newspaper clippings and heirlooms that can help you put together your ancestors’ stories. Your matches are the keys to the vault!