DNA testsPerhaps you already know that DNA testing can help you find family through online genealogy services, but maybe you’re wondering how a DNA test can do so. We’ve broken down and pieced together how DNA testing assists you, so read on to answer the question, “How do DNA tests work?”

What is DNA?

To understand how DNA testing works, let’s first have a refresher covering DNA basics. Otherwise known as deoxyribonucleic acid, DNA is a hereditary molecule that contains your unique genetic code. This code helps determine some of your characteristics, including physical traits (e.g., your eye color). Your genetic code is also partly linked to certain personality traits you may have. About 99.9% of the DNA in all humans is identical. The other 0.1% is the part of the DNA that’s unique to each individual, making each person one-of-a-kind.

DNA is hereditary and runs in your family. You get half of your DNA from your biological father and the other half from your biological mother. Your biological parents received their DNA from their biological parents, and your biological grandparents receive their DNA from their biological parents. The pattern continues as you trace DNA pathways. Because DNA is passed down your lineage, your DNA contains genetic information that other members in your lineage share. For this reason, DNA tests can be used for a variety of purposes.

What are DNA tests?

DNA tests can lead to analyses of your DNA, helping you to make a number of discoveries. Here are just some of the purposes that DNA tests can be useful for:

DNA tests can help you find your family members and ethnicity

Since DNA contains genetic information shared with lineage members, DNA tests can help you discover long-lost relatives and ancestral roots. By ordering a DNA test through a genealogy service, you can juxtapose your DNA test’s results with family tree information, helping you to trace your descent.

Online genealogy service Ancestry, for example, provides AncestryDNA, a $79 DNA test. By using autosomal testing technology and family history resources, AncestryDNA can estimate your origins to over 150 ethnic regions. The service also helps you find your kin by matching your DNA to the DNA of other AncestryDNA members. If your DNA markers match with someone else’s, it’s highly probable that you’re related to that person.

DNA tests can predict medical conditions

DNA tests can also give you a heads-up about medical conditions you may be predisposed to. For example, if you want to know if you’re at risk for a genetic condition (e.g., Parkinson’s Disease), you can order a DNA test from certain services. These services can analyze your DNA, and then they can help assess your risks for particular health conditions. Because of DNA testing, it’s also possible to check to see if you’re a carrier of various medical conditions, such as cystic fibrosis. A carrier is a person who inherited a genetic trait and doesn’t exhibit this trait, but they could pass it on to future family members.

How is your DNA collected?

The way your DNA is collected depends on the test you’re completing. Contrary to DNA collection stereotypes, many DNA tests don’t require a blood sample. A number of DNA tests, such as MyHeritage’s DNA testing service, only require you to do a simple mouth swab to collect cheek cells, while others, such as Ancestry’s DNA test, ask you to perform a saliva test by spitting into a tube. After obtaining your samples, you just mail them to a lab using the provided envelope or package. In many cases, after the lab receives your samples, your DNA, which is found in your cells, is extracted from the sample, then processed and analyzed.

Types of DNA tests

There are numerous different DNA tests that can be conducted. Here are three types of DNA tests that can help you find family members.

  • Autosomal DNA tests can be taken by all, and they can provide information regarding lineages on both of your biological parents’ sides. This test is conducted by analyzing your autosomal DNA, a type of DNA that’s found in your 22 autosomes — chromosomes in the nucleus of each of your cells. Anyone can take an autosomal DNA test because all humans carry the DNA that’s analyzed in this test. Autosomal DNA is inherited from your biological parents and their ancestors, and it contains bits of their DNA. Because you inherit all this genetic information, autosomal DNA can be viewed as a record of your family’s genes. After analyzing the DNA results, genealogy services, such as Ancestry, can look through their databases, checking for DNA matches between your test and other members’ tests. As a result, by getting an autosomal DNA test, you can learn about your lineages on both your biological parents’ sides. For this reason, of the three types of DNA tests you could take for genealogy purposes, autosomal DNA tests are arguably the most useful when it comes to tracing your lineage.
  • mtDNA tests, otherwise known as mitochondrial DNA tests, can be taken by both men and women, and mtDNA tests allow you to trace your maternal line. So how do they work? If you take this type of test, your mitochondrial DNA, found in your cells’ energy-producing mitochondria, will be analyzed. Mitochondrial DNA is passed down from a biological mother to her biological children — only biological females can pass down this type of DNA. One other aspect to note is that mitochondrial DNA remains almost unchanged when it’s passed down. Because this type of DNA is passed down in an almost original state (meaning the DNA doesn’t change much from generation to generation), the mtDNA test allows you to trace your maternal line far back.
  • Y-DNA tests obtain and compare information from Y chromosomes, so those with Y chromosomes (or males) are the only ones who can learn about their paternal line through this test directly. Here’s why: Each chromosome is made up of DNA coiled around proteins, and every person has 23 pairs of chromosomes — all found in your body’s cells. The 23rd chromosome, also inherited from biological parents, determines your sex. More specifically, humans inherit an X chromosome from their biological mother, and they can inherit an X chromosome or a Y chromosome from their biological father. These combine to make up your 23rd chromosome, and the chromosome inherited from your father helps determine your assigned or biological sex (e.g., inheriting a Y chromosome and an X chromosome would mean that you’re a biological male, whereas inheriting two X chromosomes could make you a biological female).

    Since the Y-DNA test looks at information from the Y chromosome, a chromosome passed down only through biological fathers, it can only be taken by males (the only sex that carries Y chromosomes) and provides insight into their paternal lines. To analyze test results, Y-DNA test results are compared with the results of other people’s Y-DNA tests. If the results between two test takers match or mostly match, this could mean the test takers share a common ancestor. Depending on the testing company you order your test from, you may also be able to compare your results with the results of those who share your surname, helping you to discover if you’re related to one another. While females can’t take this test, they can ask direct descendants with Y chromosomes (e.g., your father or brother) to take it and share their results.

It’s important to note that, while DNA tests can be used to discover possible relatives, understand your health risks and more, you shouldn’t make conclusions primarily based on your test results. That’s because the accuracy of DNA test results can vary depending on service you use. For this reason, it’s beneficial for you to always look at results within the context of other resources, such as your online family tree, your known family history or your physician’s input.

After reading this post, you can now answer the question, “How do DNA tests work?” To learn more about DNA tests and what they can do for you, visit our reviews of genealogy services and DNA testing blog.