Learn About DNA Testing and Family History

What DNA Testing Is and How It Works

DNA testing examines your genetic material to provide information about your ancestry, health traits, and family connections. Your DNA contains instructions that make you who you are, and it is passed down from your parents. DNA tests work by analyzing samples of your genetic material, usually collected through a saliva sample you provide at home.

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When you submit a DNA sample to a testing company, laboratory technicians extract DNA from your cells and examine specific locations on your chromosomes called markers. These markers contain variations that differ from person to person. By comparing your markers to databases of other people's DNA, companies can identify patterns that suggest where your ancestors came from and which other people in their database share DNA with you.

There are several types of DNA tests available. Autosomal DNA tests examine markers on the 22 pairs of chromosomes everyone inherits from both parents. These tests are useful for finding relatives on any branch of your family tree. Mitochondrial DNA tests look at DNA inherited only from your mother and can trace your maternal line back many generations. Y-chromosome tests examine DNA passed from fathers to sons and trace paternal ancestry.

The science behind DNA testing relies on understanding that humans share about 99.9 percent of their DNA sequence. The remaining 0.1 percent contains variations that make each person unique. When millions of these variations are analyzed together, patterns emerge that connect people who share common ancestors. According to the Pew Research Center, approximately 21 percent of American adults have used a direct-to-consumer DNA test as of 2023, up from just 3 percent in 2015.

Practical takeaway: DNA testing provides data about your genetic ancestry and identifies people who share your DNA, but results are based on database comparisons and may vary as databases grow and improve.

Understanding Different Types of DNA Tests

Different DNA tests serve different purposes depending on what information you want to learn. Understanding which type matches your goals will help you make informed decisions about testing. Consumer DNA tests generally fall into three categories based on what they measure and what they reveal.

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Ancestry tests are the most commonly used type. These tests analyze your autosomal DNA and compare it to a database of other customers to identify your ethnic background and geographic origins. Companies typically provide estimates showing what percentage of your ancestry comes from different regions around the world. For example, a test result might indicate that you are 45 percent European, 30 percent West African, and 25 percent Asian. These tests also match you with other people in the database who share DNA segments with you, potentially identifying distant cousins or other relatives you may not have known about.

Health and wellness tests examine your DNA for variations associated with certain traits and health conditions. These tests can provide information about your likelihood of developing conditions like heart disease, diabetes, or certain cancers based on genetic markers. Some tests also examine traits like caffeine metabolism, lactose intolerance, and muscle composition. It is important to note that having a genetic variation associated with a condition does not mean you will definitely develop that condition. Environmental factors, lifestyle choices, and other genes also play roles in whether diseases develop.

Specialized tests focus on specific ancestry lines. Maternal line tests trace your mother's maternal line back through history. Paternal line tests follow your father's paternal line. These tests can reach back further in time than autosomal tests because they focus on one unbroken line of inheritance. Genetic genealogy tests combine autosomal data with detailed family tree information to build comprehensive pictures of family connections.

Each test type has different accuracy levels and uses different reference populations. Tests may be more or less accurate for people of different ethnic backgrounds depending on how many people from those backgrounds are in the company's database. In 2021, the American Journal of Human Genetics published research showing that ancestry estimates for African ancestry were less accurate for individuals with African ancestry than for European ancestry individuals, demonstrating that database diversity affects result accuracy.

Practical takeaway: Choose a test type based on whether you want ancestry information, health insights, or maternal or paternal line tracing. Understand that results depend on the company's database composition and may change as databases grow.

How to Use DNA Results to Research Your Family History

DNA test results open doors to family history research, but turning genetic data into a complete family story requires additional work and research skills. Your DNA matches are starting points for investigation, not finished products. Using DNA results effectively involves combining genetic information with traditional genealogical research methods.

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When you receive DNA results, you typically get a list of matches ranked by how much DNA you share. Closest matches usually share the most recent common ancestor with you. For example, a match sharing about 25 percent of your DNA is likely a first cousin, while someone sharing 12 to 13 percent might be a second cousin. Building a family tree and examining where matches connect helps you understand your relationships and can confirm or reveal family connections you did not previously know about.

DNA matches become most useful when combined with genealogical records. Documents like birth certificates, marriage records, census data, and death certificates provide the names, dates, and places that connect genetic matches to your family tree. Many genealogy websites like FamilySearch, Ancestry.com, and MyHeritage have digitized millions of these records and allow you to search by name and time period. The National Archives and Records Administration also provides online access to many historical documents, including census records dating back to 1790.

When researching family history, start with what you know and work backward in time. Interview older family members about their parents and grandparents. Gather any family documents you have access to, including old photographs, letters, and documents passed down through your family. Create a basic family tree showing your parents, grandparents, and great-grandparents. Then use DNA matches and records research to fill in details about these relatives and extend your tree further back in time.

Working with DNA matches requires respectful communication. Some people are very interested in connecting with newfound relatives, while others may prefer privacy. When contacting matches, introduce yourself clearly, explain how you are related based on DNA data, and ask if they are interested in collaborating on research. Many people enjoy discussing family history and may have information or documents you do not have access to. However, respect those who do not wish to engage.

DNA testing companies have identified numerous cases where results revealed non-paternity events or surprise relatives. According to a 2015 study in PLoS Genetics, approximately 1 to 2 percent of people who take autosomal DNA tests discover that someone they believed to be a biological parent is not actually their parent. These discoveries can be emotionally significant, and it is important to approach results with sensitivity and consider speaking with family members about findings before making them public.

Practical takeaway: Use DNA matches as leads for research, combine results with genealogical records, and communicate respectfully with matches as you build your family history.

Privacy and Security Considerations for DNA Testing

DNA testing involves sharing genetic information with companies and potentially with other people, which raises important privacy questions. Understanding what happens to your DNA data and how it is protected helps you make informed decisions about whether to pursue testing. Privacy practices vary significantly among DNA testing companies, and regulations in this area continue to develop.

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When you submit a DNA sample, you grant the testing company rights to use your genetic information for their stated purposes. Most companies store your DNA data in secure databases and do not sell your raw genetic data to third parties without your consent. However, companies do use aggregate genetic data to improve their databases and services. Some companies allow you to opt into research studies that use your genetic information to advance medical science. Others have partnerships with pharmaceutical companies or researchers who access genetic information for specific studies.

The legal landscape for genetic privacy is still evolving. The Genetic Information Nondiscrimination Act, passed in 2008, prohibits health insurers and employers from discriminating against individuals based on genetic information. However, this law does not cover life insurance, disability insurance, or long-term care insurance. Some states have passed additional genetic privacy laws with stronger protections. It is important to review each company's privacy policy to understand their practices and your options for controlling your data.

Law enforcement has accessed DNA databases to identify suspects in criminal cases. In 2018, law enforcement used genealogy database searches to help identify the Golden State Killer suspect. This raised questions about the privacy of DNA data even when it is shared only for ancestry research. Most major DNA testing companies have policies requiring law enforcement to follow proper legal procedures to access data, and some allow users to opt out of law enforcement searches. However, if a close relative uploaded their DNA, law enforcement might identify you through their sample.

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