Menu

How Accurate Are DNA Ancestry Tests?

Medically Reviewed by Melinda Ratini, DO, MS on September 15, 2021

DNA ancestry tests may help you learn more about yourself and your familial roots. People often use DNA ancestry tests to find out their ethnic makeup and family history. However, you should be skeptical of the results of these tests since DNA testing companies that provide these services use methods that aren’t validated by independent scientists.‌

Types of Ancestry DNA Testing

There are several types of DNA ancestry tests available to the public:

  • Y chromosome testing. Y chromosome testing is exclusively used to test a direct male line. The chromosomes are passed down from father to son. This DNA ancestry test may be performed to confirm if two families sharing a surname are related.
  • Mitochondrial DNA testing. There are structures within living cells called mitochondria that provide energy to the cell. These structures may be tested because they have their own mitochondrial DNA. The DNA test can be performed on both sexes. This type of test may give you more accurate results because it includes female ancestry DNA. 
  • Single nucleotide polymorphism (SNP) testing. SNPs are the most common variations in DNA between people. SNP testing can be used to evaluate DNA from many variations across the complete set of genes. SNP testing may be more effective in providing you with details of your ethnic background compared to using Y chromosome or mitochondrial DNA testing, which only looks at single ancestral lines.

Why Take a DNA Test?

There are many reasons why you may want to perform a DNA test. Some reasons include:

  • To discover your ancestry. DNA tests may be used to trace your lineage up to ten generations back. The tests may also help you learn more about your ancestors' origins. When DNA test results are accurate, you can even find out if you have any living or recently deceased relatives.
  • To establish paternity. The most common use of DNA tests is to solve paternal disputes. Children inherit genes from their biological parents. With a DNA paternity test, a child's DNA is compared to that of the alleged father. The paternity dispute would then be resolved if the alleged father's genes showed a 99.9% match.
  • Forensic science. Like fingerprints, DNA is unique. At crime scenes, investigators will collect DNA samples such as hair, skin, semen, and blood. Forensic scientists will then analyze this DNA to help solve crimes.
  • Medical research. Through DNA testing, doctors can confirm if you are prone to certain medical conditions. Several tests may be performed to see if you’re more likely to develop a certain genetic disorder. Your doctor can offer more accurate treatment options, once they’ve determined your genetic predisposition and risk of disease.

Factors That Increase DNA Ancestry Accuracy

DNA ancestry accuracy is determined by the amount of data the test center has accumulated. There is a wide range of DNA sequences. The more DNA sequences there are of individuals from your ethnic group and ancestral geographic range, the better the accuracy rate.

DNA ancestry accuracy is also determined by the degree of intermixture in your lineage. If you come from a heterogeneous background, you may find it more challenging to trace your roots. But if the testing companies have bulk DNA data from these lineages, you may get more accurate results.

Factors That May Affect the Accuracy of Your DNA Test Results

DNA tests may be inaccurate due to some of the reasons below:

  • Companies compare their data from a database that may not produce definitive results. Most DNA testing companies use common genetic variations found in their database as the basis for testing DNA accuracy. Therefore, you may get different results if you use different companies. Some of the ethnicities from Africa, East Asia, South America, and South Asia may be hard to trace because DNA testing companies have limited DNA data in their databases to compare to.    
  • DNA testing companies are selective when it comes to looking for certain genetic variations. These variations account for a small amount of the millions of SNP contained in your DNA. 
  • Y chromosome DNA tests only look at your paternal line, so the results may be limited.
WebMD Feature

Sources

SOURCES:

American Journal of Human Genetics: “Inferring Genetic Ancestry: Opportunities, Challenges, and Implications.”

Boston Public Library: "DNA and Genetic Genealogy."

Syracuse University: "Biology Professor Breaks Down Science Behind Ancestry, Heritage Tests."

Tufts University: "Pulling Back the Curtain on DNA Ancestry Tests."

© 2021 WebMD, LLC. All rights reserved.