How Accurate Are Ancestry DNA Matches?

Not long ago, the idea of sending a sample of your saliva to a DNA testing company to learn about your family tree would have sounded like something from a science fiction novel. But today, finding long-lost relatives and revealing valuable genetic information that could potentially extend your life is as easy as spitting in a cup. So now that genetic testing has gone mainstream, consumers are wondering: how accurate are ancestry DNA matches?

People want to know that they’re getting correct information from DNA testing for two reasons.

First of all, consumers deserve to get what they pay for. After all, at-home genetic testing can range from under $100 to a few thousand dollars. So, if a company tells you that your sample will be tested in a scientific lab by professional researchers, you should be able to trust that.

Secondly, DNA testing can change people’s lives. Your DNA test can reveal new information about your parentage or a genetic predisposition for a certain health disorder, so the information it provides must be reliable.

So how accurate are these DNA tests? First, let’s discuss a little bit about how they work.

What Is DNA?

Deoxyribonucleic acid, or DNA, is your cells’ unique code of information that makes you different from every other human on earth. If you were to look at DNA through a microscope, you would see a strand that looks like a twisting ladder. Chemicals called nucleotides make up the ladder’s rungs, and groups of them form what we call genes. Your genes determine everything from your hair and eye color to what diseases you are at risk for developing in the future.

All of this information and more is organized into 23 pairs of chromosomes. Only one pair of chromosomes determines your biological sex; the rest are referred to as autosomal chromosomes. The unusual structure of chromosomes is responsible for the spool-like shape of a DNA strand, and the information in a single human cell would stretch out to six feet long.

You inherit half of your chromosomes from each parent, which is why you can often see traits of both parents in a child. Mitochondria DNA (present in males and females) is inherited from the mother, while Y-DNA (usually only present in males) is passed on from the father.

How Do DNA Tests Work?

You’re not alone if you doubt that DNA tests are truly accurate. After all, it’s hard to believe that a simple spit test from the comfort of your home could reveal a wealth of information about your ancestry, including the migration path your ancient ancestors followed to get to the region where you live today. In order to measure DNA tests’ reliability, it’s important to understand how they work.

Each company has its own process, but the basics of an at-home DNA test are fairly straightforward: you purchase the kit from an ancestry DNA service provider and follow the directions for collecting a sample. Most kits require only a small amount of saliva, either spat into a tube or collected on a swab. Once you have the sample, you ship it in the included envelope to the testing company.

You will also need to create an online account to access your information once it’s available. Each kit includes a unique access code you must enter into your account to view any information, so you can rest assured knowing that your data will remain private.

Once the DNA sample is processed and compared with your testing company’s database, you can review the results online.

So, are DNA tests accurate if they’re that simple? You might be surprised to learn that the answer is mostly yes, depending on the type.

Types of DNA Tests

So, how accurate are ancestry DNA matches? The answer to this question lies partly in which type of DNA is used. Researchers can isolate and examine three types of DNA: Y-DNA, mtDNA, and autosomal DNA.

Y-Chromosome Testing

Y-DNA chromosome testing is used to trace a family’s male line. Y chromosomes are only passed from father to son, and most biological females don’t carry the Y chromosome in their genetic makeup. Therefore, testing the Y chromosome can provide information about a man’s Y-chromosome haplogroup – the line of ancient male ancestors from which your family’s male line descends.

Mitochondrial Testing

Mothers pass down mitochondrial DNA (mtDNA) to all their children, regardless of biological sex. Since every person has mtDNA, researchers can test it universally. While Y-DNA can only convey information about your father and the male relatives on his father’s side, mtDNA provides information about all of the aunts, uncles, cousins, and grandparents on your mother’s side.

Autosomal DNA Testing

Your 22 pairs of autosomal chromosomes contain the genetic code you share with everyone you’re related to – on both sides of your family. As a result, many testing companies isolate autosomal DNA because it gives the most detailed information about your ancestry and allows labs to look for a wider range of information.

Are DNA Tests Accurate?

So, you finally get the notification that your DNA sample has been examined, and your ancestry reports are ready to view. You use your secret access code to open your account, but all you see is a long list of names you’re unfamiliar with. This might leave you wondering, is ancestry legit or not?

It’s important to remember that ancestry tests predict relationships based on the amount of DNA you share with others. The software doesn’t know how you are related – only that you share DNA. Therefore, your test results could show a mix of distant relatives you’ve never heard of, along with closer relatives you are familiar with.

Reasons for Accuracy

If you’re using a mainstream DNA testing company that employs certified technicians that work in a professional lab, it’s unlikely to find many mistakes or much misinformation in your report. However, the way your DNA is processed isn’t the only factor. The quality and breadth of the company’s database also make a difference. After all, ancestry matches are just that – matches. And without enough supporting data, there’s not much to match your results to afterward.

Comparing your DNA sample to that of others requires a large database. If the testing service you are using does not have access to a substantial ancestry DNA database, the information you receive could be incomplete if not technically inaccurate.

To increase your chances of receiving the best possible information, consider the following tips when buying an at-home DNA test:

  • Know which type of DNA the kit tests for
  • Review the company’s privacy policy, and avoid any that sell your data to third parties
  • Confirm that technicians and equipment are certified
  • Choose a service that has good reviews for customer support and guidance for interpreting results

Budgetary concerns are understandable, but the adage “you get what you pay for” stands true with DNA testing. Choosing a testing service based solely on price may result in inaccuracies, theft of sensitive information, or being left on your own to interpret the results of your DNA test.

Reasons for Inaccuracy

It’s possible for sequencing to be done incorrectly or to receive data that are inaccurate in some way. Though mistakes are rare, any type of medical testing can be wrong. The main reasons for incorrect information include:

  • User error, contamination of the sample, or not following directions correctly
  • Mistakes or mishandling at the lab
  • Biological conditions
  • Incorrect test interpretation

If customers use more than one DNA analyzing service, it’s possible to get information that seems to conflict, leaving people questioning: are ancestry tests accurate? But for the most part, this perceived error results from different organizations testing for different variants. For example, Test A may say you carry the gene for attached earlobes, while Test B does not. That could simply mean that Test B did not look for that specific earlobe variant.

You might also find that your ancestry reports that you share more or less DNA with a person than you expected. While the report may be wrong, it’s also possible that you have incorrect information about your family relationships. It can be distressing, but it’s not uncommon for an ancestry search to reveal information about paternity, adoptions, and other long-held secrets. Therefore, anyone who uses DNA testing for ancestry matching must prepare themselves for the possibility that they will learn something unexpected or even upsetting.

Interpreting Your DNA Family Relationships

Assuming your DNA sample was collected and processed correctly, you can feel confident that matches with parents, children, immediate family, and close family are correct. These matches reflect a higher level of shared DNA, which makes it easy for the program to predict a shared relationship.

It’s important to note that each familial relationship is measured by a numerical range, which can sometimes overlap. For example:

  • Parent/child relationships share the highest level of DNA, in the range of 3,600 centimorgans
  • Siblings share approximately 2,300 centimorgans of matching DNA
  • First cousins usually share 575–1,330 centimorgans of matching DNA
  • Half-first cousins, half-great uncles, and half-great aunts share around 215–650 centimorgans of DNA

By these numbers, relationship matches between parents and children and between siblings are easy to see. For example, a person who matched 3,600 centimorgans of DNA with you could not possibly be anyone but your parent.

On the other hand, predicting whether someone is a cousin, distant cousin, or half-relative can be difficult because the DNA amounts that indicate these relationships can overlap. If your DNA test results show a match of 600 centimorgans with someone, that person is definitely related to you – but the exact relationship is unclear. Therefore, the report could place matches in the wrong category.

So, inaccurate matches aren’t a reason to doubt DNA test reliability; they are simply the result of overlapping.

Do Ancestry DNA Tests Find All Relatives?

You might not see specific relatives in your DNA test results, leaving you wondering: how accurate are ancestry DNA matches? And if someone you know that you are related to doesn’t show up in your report, you wonder: are there more people missing that you don’t know about?

It’s surprising, but remember that 10% of third cousins do not share any DNA, and up to 50% of fourth cousins share no DNA. So even though they’re still related, distant cousins might share no DNA. This is one reason why building a family tree requires more than just DNA testing alone.

Science can widen your search and provide an astounding amount of new information about your genealogy. However, good, old-fashioned research is still necessary to identify distant relatives and confirm family relationships.

DNA Test Results: Accuracy

Though there is a slim possibility for mistakes, DNA testing is still the most accurate method of uncovering biological relationships. Testing can prove both paternity and maternity with an accuracy rate of 99%, and DNA testing can rule out parentage with an accuracy rate of 100%.

It’s so reliable that the U.S. government and many governments worldwide rely on it daily. DNA may be used to prove ethnicity in citizenship cases and to help reunite families who’ve been separated due to war or immigration.

How Far Back Do Ancestry DNA Tests Go?

Mitochondrial DNA, the genetic information passed to every child, allows researchers to see the furthest into history – as far as 200,000 years! That’s because mtDNA mutates more slowly than Y-DNA, remaining more accurate over generations.

Thanks to this consistency, scientists have been able to learn about the migration of ancient humans all over the world by studying mtDNA. In fact, it was mtDNA that helped researchers trace human lineage all the way back to who they believe to be our common “Mitochondrial Eve.”

On the other hand, Y-DNA can trace a direct paternal line as far back as about 10,000 years, and autosomal DNA provides information from around 1,000 years ago. However, don’t expect your at-home DNA testing kit to provide information about your family line that’s 200,000 or even 10,000 years old. Most DNA matching services only go back about 1,000 years. Of course, that’s still a long time – imagine what you could learn from 1,000 years of family history.

If you’re still wondering, “how accurate are ancestry DNA matches?” remember that DNA test reliability is not only influenced by the type of DNA being sequenced but also by how far back you look. The further back DNA testing goes, the greater the chances of inaccuracies. However, for most people’s genealogy purposes, accuracy levels are dependably high.

Is Ancestry DNA Safe?

After asking “how accurate are genetic tests?” the next most common question is: “is ancestry DNA safe?” You’ll be happy to know that the process of providing a DNA sample for an at-home test is very safe – all it requires is a sample of saliva. It’s not like you’re touching or handling anyone else’s bodily fluids (unless you’re helping someone else collect a sample), and the process is 100% non-invasive.

However, protecting your data is another issue. Hacking and the accidental mishandling of sensitive information are always concerns. So, to protect your privacy, read the user agreement carefully before signing up for a testing service. It’s natural to assume they’re all the same, but they’re not.

Some services allow you to delete your files at will, while some will admit that they might sell your DNA data to a third party. Furthermore, all companies must share their data with law enforcement and other federal, state, and local agencies if asked.

The safest companies keep your DNA information anonymous and separate from personal information like credit card numbers and addresses. Look for these indicators that your data is handled in the safest possible way:

  • The processing lab does not have access to your name or contact information
  • DNA test results are stored in a secure database
  • Any remainders of your DNA sample are stored in a secure, temperature-controlled facility with 24-hour monitoring
  • The company recognizes and follows protocol for the Genetic Information Nondiscrimination Act
  • You have the option to delete your data at any time

Your data is valuable, so it’s important to look for companies that keep your DNA as anonymous as possible; these services will provide the best possible security.

Discover More with GenealogyBank

Are you ready to see what ancestry reveals about you? GenealogyBank has helped thousands of family historians, devoted genealogists, and curious individuals with their research. Users can access more than 15,000 newspapers from all 50 states, dating as far back as 1690. Family history records, obituary archives, military records, and exclusive records not available on other genealogy sites can all be found at GenealogyBank.

DNA testing can provide a staggering amount of information about your ancestry, but what comes next? Names on a chart are interesting, but understanding who your ancestors were, where they lived and worked, and what they accomplished is much more meaningful. Visit GenealogyBank today to take your genealogy research to the next level!

22 thoughts on “How Accurate Are Ancestry DNA Matches?

    1. One reason for another test years later is that more and more people are getting DNA tests, contributing results that increase the possibility of you finding unknown-to-you relatives.

    2. I have tested with two different companies so I’m in different databases. If you want to be in multiple databases, the most cost effective way would be to transfer your raw data between companies with the companies that will do that.

  1. Thank you for this article. The write-up was excellent and easy to understand. It also provided some important information in regards to how the tests actually work and what to look for when deciding which company to pick when getting your DNA tested.

  2. The article is generally very good, but it does not explain that inheritance of genes is a randomized process, so that in each generation a child may inherit more genes from one parent than from the other. That is the reason the percentage of genes shared with other relatives can vary within the same degrees of relationship.

  3. The statement: “mtDNA provides information about all of the aunts, uncles, cousins, and grandparents on your mother’s side” is incorrect. Remember that your mother also had a father, and his sibling’s, cousin’s, aunt’s, uncle’s, and parents’ mitochondrial DNA have nothing to do with your mother’s, yours, or your siblings. Your mother’s mtDNA is only relevant to her maternal side, and even then, any cousins you have whose mother is an aunt by marriage to a brother of your mother rather than heredity will also not share your mtDNA. Relatives on your mother’s paternal side (that of your maternal grandfather in his generation and those before him) will not share your mtDNA except in unusual situations.

  4. This was very enlightening, especially regarding the percentages of 3rd and 4th cousins who may not share any DNA.

  5. I have a dilemma. My mtDNA test with FTDNA has some 150 matches, none of whom I recognize or that match what other services or family and
    official records show. I ran the test again with basically the same result. In such cases, I would expect adoption or some other parental anomaly. However, I have dozens (100’s) of matches with grandparents, cousins etc. in my maternal tree, across Ancestry, My Heritage, and 23 and me. They are consistent, with many of the same relatives repeatedly showing in most or all of these DNA sites. Most are supported by family or other records. How do you resolve a situation like this where you have 3 sites that are consistent, but a 4th is a complete outlier?

    1. Autosomal DNA will cover all relations that you share DNA with. mtDNA only measures the DNA you inherited from your mother’s mother’s mother’s mother, etc. Because mtDNA is passed from mother to child unchanged, it goes much further back than autosomal DNA. So the common ancestors on your mtDNA test go further back than all the others. Also, the cousin matches for mtDNA are all descended through the female lines only of said common ancestors while the other DNA cousin matches are descended from all your ancestors on all their lines of decent. So what you are seeing is expected of different types of DNA tests.

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