Using DNA to trace a family tree

Curious about your ancestry? Genetics can reveal health surprises, too

Three women, three generations, blowing bubbles outside.

Your DNA tells a story. Beyond what makes you yourself, it tells the story of your family and how you are connected to people around the world. Or does it? That is what genetic counselor Megan Bell, ScM, is here to explain.

“Ancestry alone isn’t necessarily genetic,” Bell said. “Just by nature, people from different parts of the world have similar gene variation, or changes within their DNA. This diversity happens the more a population intermarries or mixes, whether through emigration, immigration or being forced to leave a homeland.

“It is not as easy to identify anymore because of how global our population has become. But, these ancestry DNA tests are doing the best job they can with their collective DNA samples. They use genetic testing to discover potential common ancestors or where a family originally came from.”

Related: Which genetic tests are out there? A comparison

There are 20,000 genes in the human body, and these genes are made up of a sequence of letters. By diving deep into DNA to compare those letters, a lot of differences can be seen between people — but a lot will be the same too.

“Of all the DNA in the human body, 99.9% is similar from person to person. It is that 0.1% that is different, making each of us unique,” Bell said. “And those differences within that 0.1% are most often common among ancestors.”

Finding what makes us unique

Genetic tests for ancestry zoom in on that 0.1% to categorize differences and similarities in order to pinpoint origin. And while discovering origin can connect people with those who share their history, it can also reveal unexpected incidental findings.

“When you complete a genetic test to find your ancestry, you may be connected to family members you didn’t know existed,” Bell said. “This can be psychologically distressing. You may learn something that completely changes your family history or identity, like who your biological parent is.”

One of the biggest challenges with direct-to-consumer genetic tests is that they do not offer insight from a health care provider.

“Most people want to discover ancestry out of entertainment and curiosity. Yet, these types of findings do affect your health. For example, if you find out you have Jewish ancestry, you are going to find out you are at higher risk for certain conditions. That can be stressful or scary,” she said.

There are benefits, but there are also limitations and implications due to incidental findings, which can have a huge impact.

“I want people to know this type of genetic testing is not perfect,” Bell said. “But genetic counselors are here to help you understand all sorts of genetic testing, including for ancestry. That way you can make the best decisions for yourself.”

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