By Kathy Hughes

Contributing Columnist

In the world of family history research, DNA testing is all the rage. Unfortunately, people are often disappointed in their results for a variety of reasons, namely:

•They don’t understand the results.

•They expected more information.

•They ordered the wrong test.

Obviously, there is overlap among the reasons for being dissatisfied, and often there is a combination of factors. Even though the costs of testing have come down drastically from when DNA testing was introduced, it is still an outlay of money few can afford to waste.

Another point for confusion is choosing a company to do the testing, and the competition is increasing. On the other hand, DNA testing can change people’s lives, and, in my case, has added a ton of new interest and fun.

Advertising can be quite misleading. Don’t expect your results to reveal the time, place and cause of your death. Testing for genetic diseases is specialized and complicated. Only one company at this time, 23andme.com, is able to guess at the probability of your being a carrier of a subset of rare genetic conditions; Alzheimer’s disease is not one of them.

One question everyone should ask themselves is whether they really want to know what their DNA may show. Likewise, you should be prepared for unexpected results regarding parentage or family relationships.

I have found that, more often than not, people are unhappy, even devastated, to learn some unknown, unexpected truth. For instance, one individual who tested to be a fourth cousin, refused to accept the obvious truth when no one in her family tree was related to anyone in my tree. Clearly, there was an exceptional event somewhere in her DNA inheritance, but she was not prepared for this conclusion, even though the DNA proved otherwise. Several of her other matches had the same experience with her family history. DNA doesn’t lie — people do.

Any and every cell in our body can be tested to reveal the DNA we inherited from our parents. This form of testing is called autosomal DNA testing. Autosomal testing, as with all commercial DNA testing, is done with a sample of saliva which you send to the company. First they will send you a testing kit (after you have paid your money) which contains a test tube. You spit into the tube and send it off in the mailer they have supplied.

Autosomal testing yields some general information based on what is currently known about the human genome — the distribution of various forms of DNA throughout the world’s populations. Because human families are usually formed within a certain geographical distance, the further apart the geographical distance, the greater the difference in the DNA structure. Likewise, the further apart populations in time, such as Neanderthals and contemporary humans, the more distinctive the differences in DNA structure. (As far as I know, 23andme is the only company which provides the percentage of Neanderthal DNA you have inherited.)

The most specific information from autosomal testing is to match you with your close relatives. Since half your DNA comes from each parent, it is deduced that 25 percent comes from each of four grandparents, eight percent from great-grandparents and so on. The same formula is applied to aunts, uncles, cousins, nieces and nephews. Don’t worry about the math — the main focus of testing is to provide you with these results.

It only follows that a company can provide you with family relatedness when compared to the other DNA samples they have tested. The larger the number of samples they have, the more likelihood that they will be able to find your long, lost relatives among them.

While every testing company can provide results as to your ethnic heritage — Italian, African, Asian, etc., as well as your relatedness — if you want to find specific individuals to whom you are related, it is only to your advantage to choose a company having an enormous number of samples.

It’s fun, it’s expensive, so be aware of what you want to find out. But wait, there’s more! We covered autosomal DNA testing here; a second article will cover widely available mtDNA and Y-DNA testing.