How do DNA Test Kits Work? The Difference Between Birthplace and Heritage

At a rally on Thursday night, President Donald Trump expressed skepticism at Senator Elizabeth Warren's claims of Native American ancestry. To illustrate his point, he made some creative claims about how DNA tests work.

"You know those little kits they sell on television for two dollars?" Trump said at the rally, likely referring to genetic testing services like 23 And Me, Ancestry DNA, Living DNA and National Geographic's Geno 2.0. In reality, these kits tend to cost around $99, or up to $199.

"Learn your Heritage!" Trump continued. "Guy says 'I was born in Scotland;' turns out he was born in Puerto Rico, and that's ok. That's great."

23 and Me
A woman opens a popular DNA test kit from the company 23 and Me. It will not help her understand what country she was born in, but she may already know the answer to that. CLAUDIO REYES/AFP/Getty Images

However, a personalized DNA kit cannot tell someone where they were born. That's something that you might ask your mother about.

Instead, the function of a DNA kit is to help you estimate your genetic ancestry. If a set of full siblings were each born on different sides of the world, they would still have the same genetic ancestry.

However, some scientists dispute the accuracy of these tests. Since there is no worldwide database of human DNA indicating at what locality different genotypes evolved, it's very difficult to find an accurate read of DNA. Some scientists call them "recreational genetics." The kits can't tell you exactly where your ancestors lived or what ethnicity they identified with, but they can tell you if a lot of people who lived in a certain vague geographic area share similar DNA to you.

A DNA test may help determine whether Warren has any Native American blood, or it may not. The National Congress of American Indians says DNA testing can be useful, but they don't guarantee eligibility for someone to enroll as a tribe member. On the other hand, a DNA test has been used to remove tribal members who didn't appear to share a genetic link with that tribe.

DNA test kits include items for collecting DNA, such as a small container into which the customer will spit, or a swab to collect cells from the inside of their cheeks. The customer then sends the kit off to a lab, where scientists isolate their cells and analyze their genes. Then they compare the alleles from your genes with the alleles in their databases—although different companies have access to different databases, which means you could get different results depending on which product you use. When your DNA shows similarities to certain locations, you get a report describing your heritage.

Where you live, where you were born, where your mother lived while pregnant with you, and where you were conceived have absolutely no bearing on your genetics.

Continuing his point, Trump described a situation in which he would "gently" throw a kit to Warren in the hopes that she would use it to prove her ancestry. "Because we're in the 'Me Too' generation, so we have to be very gentle," Trump explained. "And we will very gently take that kit and we will slowly toss it, hoping it doesn't hit her and injure her arm, even though it only weighs probably two ounces."