DNA is all the rage. Television commercials promise us that we can determine our precise ancestral origins. But it’s not quite that simple. People take DNA tests for a variety reasons. Some are looking for ethnicity estimates. Some are looking for health reports. Adoptees might be looking for biological family members. In terms of genealogy, or family history, DNA is very good at helping a researcher to prove a hypothesis, confirm or disprove an existing family tree, identify living relatives, and estimate general ethnic origins. Overall, DNA is a tool to add to your family history research.

There are ethical and privacy issues which should be considered before taking a DNA test. DNA can reveal unexpected results. A father may not be the biological father; a sibling may only be a half sibling; an unexpected adoption may become obvious. No one should take a DNA unless they are prepared for the unexpected.

Every person who takes a test owns their DNA, not the companies with which they test. Those who manage kits for others do not own the DNA that is now their own. In terms of health care, the Genetic Information Nondiscrimination Act (GINA) protects against genetic discrimination for health insurance or employment. However, this law does not apply to life insurance, disability insurance, or long-term health insurance.

The biogeographical estimates, more commonly referred to as “ethnicity” estimates, are the least accurate part of DNA testing. Each DNA company uses a different algorithm and a different reference population to determine the ethnic origins of individuals. These results are very accurate at the continental level. As the pool of test-takers increases and as the science improves, these estimates will likely improve as well.

There are a number of testing options in the marketplace. The most common direct-to-consumer tests are from AncestryDNA, Family Tree DNA (FTDNA), Living DNA, My Heritage, and 23andMe. National Geographic’s Geno 2.0 provides results for deep ancestry and is not suitable for most family historians looking to identify specific individuals. For names of other testing companies, check with the International Society of Genetic Genealogy. With most of these companies, your results can be loaded to third-party sites where you can compare yourself or your family members to other individuals who tested elsewhere.

The five main testing companies all provide data on autosomal (at) DNA. Only FTDNA currently provides detailed information about the direct male and female lines (Y-DNA and mt-DNA). Y-DNA is only passed from fathers to sons, but everyone inherits mitochondrial (mt) DNA from their mothers.

Autosomal DNA is passed from both parents to their children and is a very useful tool for family historians. Children receive 50 percent of their DNA from each parent, though siblings won’t inherit the identical DNA to each other. Each child receives about 25 percent of their DNA from each grandparent, about 12.5 percent from each great-grandparent, about 6.25 percent from each second great-grandparent, and only about 3.125 percent from each third great-grandparent. After about the second great-grandparent level, some DNA will randomly begin to drop off of your genetic family tree. Similarly, you will always share DNA with up to your second cousins, but you won’t always share DNA with every cousin more distant than that.

When you begin to test your family members, try to test vertically before testing horizontally. In other words, pick the oldest generational relatives, or the relatives “closest” to your ancestors.

DNA is a great way to add to your family tree. However, the prevalence of adult adoptions in Japan to carry on the surname can complicate this situation. In the Okazaki family, the individual who was adopted to carry on the surname (yōshi) was a maternal relative. He shares DNA with Okazaki descendants in the U.S., but at the cousin level. He does not share Y-DNA with the other male Okazaki descendants, because he is from the maternal Maihara line. Other times, an adoption may occur entirely outside of the family circle and no DNA is shared at all.

People often wonder which test they should purchase. They ask, “which test is best?” The answer depends on several factors. Consumers should first consider why they want to test. Look for a test which allows you to link to your family tree (Ancestry, 23andMe, MyHeritage, FTDNA). If you are interested in wellness traits, consider testing with 23andMe, or simply load your data to a third party site for a nominal fee, such as Promethease. Some individuals can’t generate enough saliva to test at Ancestry or 23andMe, so they opt to test at a company which uses a cheek swab (FTDNA, MyHeritage, Living DNA). Ancestry has the largest database of all the main companies and is very user friendly. Living DNA is UK-based and does not currently link to family trees. MyHeritage has a large European database. As mentioned, only FTDNA offers Y- and mt- testing.

With the holidays right around the corner, the testing companies will likely have sales. Order your kits when the price is right and get started. Once your results come in (usually six to eight weeks, depending on the company) be sure to link your results to your family tree. Contact your matches. If you need more help getting started or understanding your results, consider taking a class at your local genealogical society, family history center, or even online. DNA is just one more piece of evidence to add to your family history journey.

I wish to thank Ancestry.com for participating in the Nikkei Angel Island Pilgrimage this year, and for donating over 100 DNA kits to our attendees.

Linda Harms Okazaki, a professional genealogist, is the past president of the California Genealogical Society. She specializes in Japanese American records. If you have a genealogical question which might be answered in this column, please send an e-mail to LindasOrchard@gmail.com. The views expressed in the preceding column are not necessarily those of the Nichi Bei Weekly.