Over the past few years, DNA home test kits like 23andMe and Ancestry.com have made their way onto the shelves of virtually every drugstore in the country. Whether you want to learn more about your family heritage, understand your risk for certain diseases, or discover unknown relatives, these autosomal DNA test kits — which range in price from about $60 to $100 — appeal to the curiosity in many of us.

But before you swab and ship in your DNA sample, there a few caveats to keep in mind, say faculty experts in genetics and genealogy at the California State University.

1. These tests won't tell your whole genetic story. At least not yet.

"You can't sequence a human genome for 100 bucks," says Jason Bush, Ph.D., associate professor of biology at California State University, Fresno. Each human genome is made up of about three billion base pairs — the basic building blocks of DNA that combine in sequences (C + G, A + T, etc.) of complementary pairs to make up a strand of DNA. To sequence one person's entire genome — which means determining the order of DNA bases that make up your unique genetic line-up — previously cost upwards of $10,000, Dr. Bush says.

In contrast, $100 at-home DNA tests use technologies that capture perhaps half a million to one million different spots along your genome, he says, explaining that this sample is essentially a snapshot of sections where variations are known to occur. Each DNA home test company may be taking a different snapshot, too.

That said, due to the growth in the industry, the cost of sequencing an entire human genome is dropping and could be near $100 in the next few years, according to the San Diego Union Tribune.

2. Results can vary. A lot.

Most people use an at-home DNA kit to learn about their ancestry and ethnic heritage, says Colleen Greene, a genealogist and librarian at California State University, Fullerton's Pollak Library.

"Ethnicity results at a continental or regional level are pretty accurate," Greene says. Meaning that tests are good at telling you if, say, your ancestors came from Northern Europe or East Africa.

But if you're trying to get information on a more granular level — like finding out exactly how Irish you are — results are less precise, explains Greene, who also teaches a graduate genealogy course at the School of Information at San José State University.

"Autosomal DNA ethnicity estimates really tell us ethnicity from about 500 years ago," she says. "People often do not understand that and get confused because they know their ancestors lived in, say, Ireland, 150 years ago."

And because each company takes a different snapshot of your genome, ethnicity findings can vary significantly from one kit to another. "[Since] they're not all sequencing the same stuff… [it] leads to variable results," says Bush. For example, one test may say you're 50 percent Portuguese, while another may say 30 percent.

Greene adds: "In addition to these differing snapshots, testing companies also use different algorithms to analyze those snapshots, different reference populations to compare data, and different categories for grouping ethnicities."  

However, when it comes to matching your DNA against a database to find a family match, the results are very accurate, says Greene. So if you're willing to allow the testing company to reveal your identity or alias to others who share a genetic match with you, those people could be notified of a possible biologic family match.


3. Whatever information you get from a test, use it wisely.

In addition to ancestry information, one service — 23andMe — is authorized by the Food & Drug Administration to issue reports on genetic health risk and genetic carrier status, such as whether or not someone carries the BRCA1 or BRCA2 gene mutation, which is associated with an increased risk of breast and ovarian cancer.

Bush cautions that information like this should be taken with a grain of salt, since risk does not translate to disease, and false positives (in this case, when you're told your risk for a disease is higher, but in fact it's not) are common. Greene adds that if consumers have a question or concern, they should take any results to their doctor for further discussion.

On the other hand, learning about your potential for developing a certain disease while you're healthy can also be beneficial. "Knowing about one's family health history can be really empowering," stresses Bush, adding that not enough of us ask relatives about diseases in our family history, so we have an incomplete picture of our health risks. This knowledge can be a big help in informing medical decisions.

This is of particular importance to Bush, who specializes in cancer cell biology and researches the genetics of cancer to better refine treatment for patients. "I'm a firm believer that information is power," he says, referring to the widely publicized decision by actress Angelina Jolie to undergo a double mastectomy after testing positive for the BRCA gene.


​​​3 Kinds of DNA Tests

  1. Autosomal: This type is used by the major direct-to-consumer DNA test kit companies. It looks at chromosomes one to 22, also known as autosomes. Autosomal tests are generally used for family genealogy projects.
  2. Mitochondrial: This test only looks at the mitochondrial DNA passed from mother to child. These tests are used to explore the direct maternal line, generally for deep ancestry and anthropologic research.
  3. Y-DNA: This test looks only at the Y chromosome, which is inherited from father to son, so it can only be done in males. Like mitochondrial, Y-DNA testing is also used for tracing deep ancestry going back thousands of years.

Both Y and mitochondrial testing methods are used by Family Tree DNA and National Geographic's Genographic Project, and mitochondrial tests were used to identify the remains of England's King Richard III.

4. There are federal laws to prevent DNA discrimination (sort of).

What if your home DNA test results turn up a significant risk for Parkinson's or late onset Alzheimer's? You might wonder, Will my insurance company discriminate against me if they find out?

Generally not, if it's health insurance. The Genetic Information Nondiscrimination Act of 2008, also known as GINA, prevents discrimination by health insurers, as well as by any employer with more than 15 employees.

However, the law does not cover life insurance, disability insurance or long-term care insurance. For example, a life insurance company could choose to refuse to issue you a policy if they learned you had the BRCA gene mutation. And a federal bill introduced to the House of Representatives in 2017 would exempt employers with workplace wellness programs from GINA rules, meaning they could offer better benefits to people in "good" genetic standing.

California residents may have a bit more protection, thanks to CalGINA, which was signed into law in 2011. It extends the scope of the federal GINA rules to prohibit genetic discrimination in emergency medical services, housing, mortgage lending, education, and state-funded programs.  

gene sequencing results now joins things like our credit card numbers in the pool of information available to be stolen by hackers and used for purposes we never authorized or imagined. — Janet Stemwedel, Ph.D., San José State university 

However, while state and federal GINAs are supposed to limit how health insurers could use our genetic information, "we are seeing efforts at the national level to give insurers much more freedom to identify extensive lists of preexisting conditions and exclude people with those conditions from coverage," says Janet Stemwedel, Ph.D., professor and chair of the Department of Philosophy at San José State University, where her teaching and research focus on the philosophy and ethical conduct of science. "It is not a moment where I have a lot of confidence that the results of a direct-to-consumer (DTC) genetic test will have no impact on the consumer's ability to get health insurance."

And then there's the question of privacy and data security. "The gene sequencing results provided by DTC companies now joins things like our credit card numbers in the pool of information available to be stolen by hackers and used for purposes we never authorized or imagined," says Dr. Stemwedel.

Just this week, lawmakers in Iowa and New Jersey sent letters to four DTC testing companies pushing them for details on their privacy policies. And the Federal Trade Commission recommends that consumers scrutinize each company's website for details about what they do with your personal data.

5. Be prepared for surprises.

If you take a DNA test to learn more about your ancestry, you may find out information you aren't entirely ready to hear. "I tell people to go into it expecting a surprise," says Greene, who does private genealogy work. "I have worked with family members who find out they have a half-sibling or an unknown biological parent on the day the test results come back. It can be really upsetting for people."

Another word of advice, says Greene: If you're helping a family member to submit a test sample, you need to get informed consent. "They need to understand how the DNA will and can be used, and be made aware of the risk that if someone in their family has committed a crime, there is a potential for them to be discovered." Familial DNA matching was in fact how James DeAngelo Jr., the suspected Golden State Killer, was found earlier this year.

Big Data on Our DNA

Direct-to-consumer genetic biotechnologies are still in their infancy, and they're not going away any time soon, says Bush, explaining that as these companies continue to amass data about the human genome, their scientific legitimacy advances.

For example, in March 2018, 23andMe received the first-ever FDA authorization for a direct-to-consumer genetic test for cancer risk. "[This] allows 23andMe to provide customers, without a prescription, information on genetic variants found on the BRCA1 and BRCA2 genes," he says.

While the science backing grows, so do the businesses. Dr. Stemwedel points out that these companies may be profiting from your data in more ways than one. For example, your genetic and survey data could be used to develop patented inventions, which you would have to pay for again for to partake in. "It's not clear to me that most of the people ordering their test kits and spitting into a sample tube have thought about this part of the business model," she says.

Greene looks at it from a greater good perspective: "People can help science by checking 'yes' to allow their DNA to be used for research purposes during their test registration. The more people who contribute DNA samples, the larger our testing population becomes," she notes, "which helps researchers understand more about hereditary diseases and perhaps discover new ways to prevent them."

The CSU Fullerton librarian and genealogist is passionate about how genetic genealogy helps make science more accessible in everyday life. "What other subject intersects disciplines from anthropology to archaeology to biology to history to criminology and ethics?" she says, adding that her April 2017 talk on genetic genealogy at Fullerton drew a standing room-only crowd. For fall 2018, she's planning an interdisciplinary exhibit and program series in collaboration with CSUF Science Librarian Robert Tomaszewski, Ph.D.