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The journey to discover who we are—where we originate from and what we’re composed of—is a shared human pursuit. This deep-rooted curiosity about ourselves has led to a flourishing market for personal DNA testing. Over 12 million individuals have used services like 23andMe and AncestryDNA to have their DNA analyzed, and this number is projected to continue growing rapidly in the next few years. But do these DNA tests really provide the in-depth answers about our ancestry and health that we desire? Here are 13 essential insights about these personal testing kits.
1. PERSONAL DNA TESTING IS EASY—IT ONLY TAKES A LITTLE SPIT.
Generally, you simply need to provide a saliva sample or swab the inside of your cheek, then place the sample in a container and send it off to the lab using the pre-labeled envelope or box. Six to eight weeks later, your results will be available online.
Most personal DNA testing kits are fairly affordable: Options from major players like 23andMe, AncestryDNA, Family Tree DNA, MyHeritage DNA, and Living DNA typically range between $69 and $199. The price can vary depending on which genetic reports the customer selects: For example, a 23andMe test focusing solely on ancestry is less expensive than one that includes health data. Refer to this Wiki chart from the International Society of Genetic Genealogy to compare what different companies offer.
2. THE KITS DETECT GENETIC VARIANTS KNOWN AS SINGLE NUCLEOTIDE POLYMORPHISMS.
After extracting DNA from your cheek swab or saliva, DNA testing companies analyze your genetic code for specific variants. DNA is composed of chemical building blocks called nucleotides, which are represented by four types—A, T, C, and G (adenine, thymine, cytosine, and guanine). With 3 billion pairs of these bases, making a total of 6 billion letters, they form your genome, a unique genetic sequence.
Testing companies identify which of the four bases is present at various locations in your genome. Since much of our genetic sequence is similar, the focus is on single nucleotide polymorphisms (SNPs), which are variations that differ between individuals. Many SNPs are biologically significant. For example, one SNP near the OCA2 gene, which affects the production of the pigment melanin, can make it more likely for someone to have blue or green eyes. Certain SNPs are linked to traits and even diseases, with some associations being stronger than others.
3. THE ACCURACY OF KITS CAN DEPEND ON THE TESTING METHODS USED.
According to 23andMe spokesperson Scott Hadly, the company can accurately identify SNPs with 99.9% precision, which is typical for the methods they employ. Since many other prominent companies use similar approaches, their accuracy likely falls within the same range. However, not all tests meet the same standards. Recently, one test failed to detect that a supposedly human DNA sample actually came from a golden retriever named Bailey. It did, however, suggest that based on her genetics, Bailey should take up cycling and basketball. Bailey's results came from the playful Superhero DNA Test, which claims to provide insights into strength, speed, and intelligence. This test analyzes just four genetic variants, whereas more expensive kits may analyze tens of thousands of variants. It's important to note that, regardless of how many variants a kit examines, it cannot predict complex traits like intelligence, which are shaped by numerous genes and environmental factors.
You should avoid companies that make questionable predictions about your ideal diet, sports abilities, or other dubious recommendations. Experts warn that using DNA tests to make these extrapolations is, at best, premature, and at worst, pseudoscience. The conclusions often stem from just a few studies focused on specific groups, typically white men. "Results gathered from one population are not always applicable to other populations," says Jason Rosenbaum, an assistant professor at the University of Pennsylvania's medical school, in an interview with Mytour.
4. DNA CAN UNCOVER GENETIC LINKS—BUT SOME POPULATIONS ARE UNDERREPRESENTED.
Companies use various techniques to trace ancestry, but most tests compare your DNA to reference samples that represent populations from different regions. Since many people have mixed backgrounds, ancestry is usually shown in percentages: 26% Polish, 14% Greek, and so on.
These tests cannot definitively tell where your ancestors lived, as they cannot compare your data to DNA from individuals who lived centuries ago, as noted by British geneticist Adam Rutherford in an interview with Gizmodo. Moreover, not all population groups are equally represented in the reference data, which can affect the accuracy of your results. People of European descent are overrepresented, while there are fewer references for individuals with roots in the Middle East or Asia, for example. However, as research expands to include more diverse populations, companies are refining their analyses to offer more comprehensive ancestry details for individuals worldwide.
5. SOME CLUES ABOUT YOUR DNA'S ANCIENT PAST—INCLUDING NEANDERTHAL ANCESTRY.
All living humans can trace their mitochondrial ancestry back to a woman known as Mitochondrial Eve, who is believed to have lived in Africa around 150,000 to 200,000 years ago (though this remains a topic of ongoing debate). She wasn't the first modern human woman, nor the only woman alive at that time; other women from her era also have descendants today, but none have an unbroken line of female descendants like Mitochondrial Eve.
Mitochondria, the energy-producing structures in our cells, are inherited from our mothers. Some DNA testing companies provide mitochondrial DNA tests that help you identify your maternal haplogroup, which includes individuals who share a common maternal ancestor from thousands or tens of thousands of years ago.
Men can explore their paternal lineage through the Y chromosome, which is passed from father to son. Specific SNPs on the Y chromosome can be used to identify a person’s paternal haplogroup. (Women can trace their paternal haplogroup through their biological father or brother.) There’s also the concept of "Y-chromosomal Adam," although scientists disagree about whether he lived around the same time as Mitochondrial Eve.
A home DNA test might even reveal that you have a bit of Neanderthal ancestry, which is especially common among people of Caucasian and Asian descent. Don't be concerned by the Neanderthals' reputation as primitive brutes. We now know they were intelligent, used tools, and had their own complex culture.
6. YOU MAY DISCOVER RELATIVES YOU DIDN'T KNOW EXISTED.
Many DNA testing platforms allow users to see if they have any biological connections with others using the same service. This feature can be a valuable tool for those building detailed family trees or for adoptees looking to trace their biological roots. Several individuals have even unearthed siblings they had no idea existed through these services. In one instance, two women—one adopted through an agency and the other adopted by a family who found her abandoned in the woods as a baby—discovered they were long-lost sisters.
However, not everyone is thrilled about uncovering hidden family ties, so it's important to move carefully if you decide to allow a company to match you with potential relatives.
7. DNA TESTS CAN PROVIDE HEALTH INSIGHTS …
While genetic testing might reveal something as quirky as your inability to detect the smell of asparagus urine, most people are more interested in learning about potential genetic variants linked to serious conditions like Alzheimer's or breast cancer.
Genetic risk is fundamentally about probability. For instance, discovering that you have an SNP linked to a tenfold increase in the likelihood of a disease might sound alarming—but if that disease affects only 0.01 percent of the population, your risk is still just 0.1 percent. Even if you carry an SNP strongly associated with a more common condition and show symptoms, it's crucial to consult a doctor for a proper diagnosis.
Having a disease-associated SNP does not constitute a diagnosis. Rare variants, in particular, are more prone to false positives: when a variant is found in only one in a million people, a positive result is more likely to be a mistake compared to a more common variant. Some companies report on genetic variants that medical professionals haven't yet considered useful for testing—so meticulously analyzing each SNP may be of questionable value. Shoumita Dasgupta, an associate professor in the biomedical genetics program at Boston University, explains to Mytour that healthcare providers typically avoid ordering tests for these SNPs "because professionals have determined that the predictive value of these tests is limited."
8. … INCLUDING YOUR RISK OF CERTAIN CANCERS.
In March 2018, the FDA approved 23andMe to provide customers with information about specific mutations in the BRCA1 and BRCA2 genes that significantly raise the risk of breast and ovarian cancer. Some individuals with a mutated BRCA gene take steps to reduce or detect cancer early, such as opting for preventive double mastectomies, a move famously made by Angelina Jolie in 2013.
However, an important note: This test only examines three SNPs in the BRCA genes that are linked to a substantial increase in cancer risk. A positive result should prompt a doctor’s consultation, but a negative result doesn't guarantee freedom from cancer risk, whether hereditary or otherwise.
9. CERTAIN DNA TESTING KITS REQUIRE A PRESCRIPTION.
GeneSight is intended to identify which psychiatric medications are most suitable for a specific patient. Fertilome is designed to detect genetic markers linked to an increased risk of fertility issues, helping individuals make reproductive choices, such as whether to freeze eggs or attempt another round of in vitro fertilization. However, both tests have faced criticism from experts who argue there isn't sufficient evidence to support their clinical usefulness. They are also costly: Fertilome is priced at $950, while GeneSight can run into several hundred dollars (although some insurance plans may reduce the cost to zero).
10. MORE DATA DOESN'T ALWAYS MEAN BETTER RESULTS.
As the cost of DNA analysis continues to decrease, some companies now offer to sequence an individual's entire DNA, analyzing all the base pairs, rather than just focusing on SNPs. Sequencing is crucial in research and medicine: Dasgupta notes that some physicians are now ordering full sequences of multiple genes or even entire exomes (the protein-coding parts of the genome) for patients.
Exome sequencing is valuable to doctors and researchers because it enables the detection of genetic variants beyond the common SNPs. However, like all tests, it carries the risk of false positives, and excessive testing increases the likelihood of receiving inaccurate results. Rosenbaum compares this to MRIs: "It's one reason why we don't just give MRIs to everyone, because you're going to find things that make you think there's a disease when there isn't."
11. YOUR DNA RESULTS MAY CONTRIBUTE TO RESEARCH ADVANCEMENTS.
Some DNA testing services invite customers to join research initiatives, asking them to provide information on various aspects of their lives, such as sleep patterns and personality traits. This data helps uncover new connections between genetic variants and specific traits. "In genetic studies, the more participants there are, the more likely it is that the study will pinpoint genetic factors affecting the trait or condition under investigation," says Dasgupta.
With access to millions of users' genetic data, personal DNA companies have a unique opportunity to make such connections. 23andMe, for instance, has already made preliminary discoveries linking genetic variants to traits like detached earlobes and the risk of Parkinson's disease. Although studies relying on self-reported data come with some limitations, they are commonplace in research, especially when collecting objective data is challenging or impossible. As research continues, it will become clearer if crowdsourced studies like 23andMe’s can become a valuable tool in the geneticist's arsenal.
12. YOU COULD POSSIBLY EARN MONEY FROM YOUR DNA.
Genos, a DNA testing company, charges $499 for full exome sequencing and offers the option to connect customers with genetic researchers. Research partners may pay between $50 and $250 to Genos users for completing studies aimed at discovering links between their genetic data and various conditions like dementia, cancer, or infectious diseases. Similarly, the emerging company Nebula offers to sequence customers' genomes, protect them with blockchain technology, and allow users to manage their data, including selling it to biotech or pharmaceutical companies in exchange for cryptocurrency like Bitcoin. However, privacy concerns remain, as there's no guarantee that companies renting or purchasing genetic data will keep it secure.
13. YOUR DNA COULD ONE DAY AID IN CRIMINAL INVESTIGATIONS.
In a recent case in California, authorities arrested a man suspected of being the Golden State Killer, believed to have committed multiple rapes, burglaries, and at least 12 murders across the state between 1976 and 1986. The breakthrough came when DNA from a 1980 murder was analyzed. Investigators created a false profile on the genealogy site GEDMatch and uploaded the genetic data, hoping to find potential relatives of the killer. The tactic worked, and with the help of genealogists, they traced the DNA to 72-year-old Joseph James DeAngelo's home in Sacramento. DeAngelo had been a police officer during the early years of the crime spree.
This case has raised significant ethical and privacy concerns among experts. DNA can be stored indefinitely, and the data from one person’s genetic profile could be used to draw conclusions about their biological relatives, even if those relatives haven't taken DNA tests themselves.
