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Choosing a DNA test

Hopefully you have read DNA part 1, in which I talked about why to take a test, and ethnic estimates. Let’s start here with some other fundamentals.

We are the literal embodiment of our ancestors

As many people know, we inherit about 50% of our DNA from each parent – which means we get roughly 25% of our genetic material from each of our grandparents, 12.5% from our great-grandparents and only about 6% from gg-grandparents. It’s the law of diminishing returns.

Keep in mind these are rough estimates, because how much we inherit from our ancestors is random. We may get only a half percent from one gg-grandparent, but 15% from another gg-grandparent — and that can make things challenging later on.

There are a multitude of TV and movie crime stories involving catching killers through DNA. To be clear, while genealogy DNA testing can and is being used for that, it’s a recent development (more about that in a future column.) Forensic genealogy is about solving crime by ruling out everyone except one person through DNA.

Genetic genealogy is the opposite — it’s about trying to find as many relatives as possible, especially ones you didn’t know existed before. We do that to find living relatives, who may be the key to finding our common ancestors.

What kind of DNA are we talking about here?

The most common genealogical DNA test is an autosomal test (at-DNA), although you’ll rarely hear that term. This test is reliable to about five to six generations back, by finding people who share DNA with you on all of your branches.

All four of the major testing companies sell autosomal tests, but they vary in their names for it. Anyone can take this test.

There are two other kinds of DNA tests, which I’ll address the next column.

Who’s the best?

Probably the most common question is, “Which is the best test to take?”

There are four major companies (and one minor one) offering autosomal DNA tests:

• Ancestry is the largest genealogy company offering tests (they also have the largest database of genealogical records), with about 19 million tests in their genetic database. Not coincidentally, they’ve also done the most commercials trying to get you to buy their tests (and services).

• 23andMe is the second largest DNA company, with a database of 12-13 million test-takers.

• Far behind the giants in numbers are MyHeritage (4-5 million) and FamilyTree DNA (1.5 million).

• Living DNA, a fifth company that specializes in UK DNA, recently joined the party and has about 300,000 test takers.

So which is the best company to plunk down your $60-$100 for their test? There’s not much difference between the tests in terms of quality, and they all measure the same thing — how much DNA do you share with the other people in their particular database.

They all also give you ethnicity estimates.

As I discussed in Part 1, many take the test for ethnicity estimates, which varies a bit from company to company, but not in a major way.

Each company uses its own algorithm or formula to measure the slippery term of ethnicity, mostly by using a combination of reference populations and others who have tested in their database.

How each company measures and reports your DNA results is a factor is deciding which is the “best,” but really, most genetic genealogists recommend Ancestry as your first test. Size does matter. Simply put, the more people there are in a database, the better chance you’ll have of finding genetic relatives that are closer to you — and that’s the real strength in DNA tests.

How does it start?

When you buy a test, you open an account and the company sends you a DNA kit via mail.

If you received it as a gift, you’ll need to open an account, and then send them a sample. This involves sending them your saliva, not blood, so it’s painless.

With three of the four companies, you spit in a tube. With FamilyTreeDNA, you swab the inside of your cheek.

In all cases, you send back the samples in a pre-paid envelope, and the company takes two to six weeks to process it.

Results are not mailed — you access them online. So, you need access to a computer or mobile device or know someone else with one who can help you.

Dealing with those results will be discussed in upcoming columns.

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