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DNA Testing 101 - How does DNA testing work?

Updated on: July 2, 2021
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To the end consumer, DNA testing is reasonably straightforward; follow the instructions on the kit and let the service tell you about your genetics. However, advanced technologies power affordable at-home DNA testing, something that would have been impossible only a few decades ago. This guide will run through DNA testing 101:

  • What DNA is
  • How it works
  • Who should undergo a DNA test
  • How to do a DNA test
  • What to do immediately after

The concept of genetics started over 150 years ago, with experiments on pea plants by Gregor Mendel. The field has evolved into a refined science with humongous strides, especially over the last two decades. The first human DNA test was completed in June 2000 at the cost of an estimated $150 million

DNA Testing 101 - How does DNA testing work? 1

What is DNA?

Let’s begin with an overview of what DNA is. DNA is…

  • One of the building blocks for human life
  • Contained within every living cell
  • A chemical blueprint that directs the actions and growth of each cell
  • Packaged into, and protected by your 46 chromosomes
  • Inherited from your parents

Every cell in your body contains DNA. Those genes were copied in equal measure from each of your parents, but the combination of your genes is unique unless you are an identical twin. It’s the inheritance of DNA that results in some traits or disease being genetic. It’s also how you can trace your DNA backward and explore your ancestral roots. 

GoalTrace Father’s LineTrace Mother’s LineFind Family
TestY-DNA testmtDNA TestAutosomal

We took every DNA test so you don't have to. Read our 2021 review of the best DNA tests.


Who should undergo a DNA test?

There isn’t a right or wrong type of person to undergo DNA testing. 

Genetic testing is safe and it’s an option for anyone who wants to learn more about themselves regarding health or heritage. 

However, before taking a DNA test, it’s important to understand the pros and cons of genetic testing and to fully understand what a test might reveal. For some, genetic testing opens a Pandora Box they would’ve been happier leaving sealed.

At-home DNA testing is fun and informative, so if you believe that learning about health risks or exploring ancestry could be painful or difficult for you, it’s probably better to forego testing.

How to do a DNA test?

DNA test kits vary from company to company, but most follow a general procedure:

How to Take an At-Home DNA test

  1. Order Your Kit

    You’ll want to research your options and narrow down the selection based on customer reviews and your personal needs. Most services let you order online and receive your test kit in the mail.

  2. Receive the Collection Kit

    Once you receive the kit, it’s time for DNA collection. You’ll take a cheek swab or spit into a tube. Each kit comes with a set of instructions to follow for DNA collection and submitting your sample.

  3. DNA Lab Receives and Process Your DNA Sample

    The testing lab extracts DNA from the cells you submitted and scans them for thousands of variations throughout your genome.

  4. Analyze Your DNA Data

    This final step makes it possible for you to learn more about yourself from the sample you submitted. The testing company will provide you with results based on medical research and its database of other samples. Depending on the test you used, you’ll gain access to information about your medical risks and your ancestral lineage.

Once you get your DNA data -

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We’ve compiled a list of dos and don’ts for anyone undergoing a DNA test:

Do:

Protect your data

Make sure you know how your DNA data will be managed, secured and whether or not a company will share it. Your DNA is a blueprint of you and you should do everything you can to protect it. Every service has an option to download your raw DNA data and then delete it from their database. Once you’ve done this, consider deleting it from their system.

Download all of your data

You never know what is going to happen to DNA testing companies or data. Considering that it is your data, even if you can’t understand or decipher it, you should always have your backup. Every service has an option to download your raw DNA data for an extra level of safe-keeping.

Upload your data to other reputable DNA sites

Manually sharing your test results with other databases helps you get a more comprehensive look into your results. Just remember exposing your DNA data to more parties means you’ll need to take further precautions.

If you’ve opted for health-related analysis, explore your outcomes

At-home testing is not meant to be diagnostic. If you learn about a health concern, don’t panic. Share your results with your doctor and discuss your options. You should never use at-home DNA testing alone to make important health decisions.

Review your shared matches

Your DNA test results can be used to confirm suspected relations or explore your family tree. It’s rare, but you could find long-lost relatives or notable ancestors as a result of DNA testing.

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Don't:

Give too much weight to the results

At-home DNA testing is cheap, easy, and fun. It can also provide important information. But you shouldn’t be making important health decisions or significantly changing your life based on results. 

It’s also important to remember that DNA tests like 23andMe don’t take your lifestyle into account. You might already be managing your genetic risk for certain diseases, so there’s no need to worry.

View your DNA test results as a starting point for improving things, but don’t see it as the end-all-be-all for informing your decisions.

Assume the results are static

Companies regularly update their algorithms based on current science. They also update their databases as more people submit their results. Checking on results periodically can give you new information. Weigh these updates against whether or not you delete your results for security reasons.

Draw hard lines with ethnicity results

DNA testing results can point you in the right direction regarding ethnicity, but won’t give you a complete picture. Again, these tests are a good starting point but don’t provide all of the information you’ll need.

Leave your data with the site indefinitely.

Despite the potential to learn more from database updates, it’s still a good idea to delete your raw data once you’ve downloaded it. Data breaches and leaks occur and you should do what you can to protect your personal information.

Give too much weight to the results
This has been mentioned several times already, but this industry is still taking its first baby steps. These tests are relatively cheap compared to the ones administered by a doctor, but they are not required to be as thorough or accurate. While they can provide valuable information, no one should make life-altering plans based on the results without consulting with a medical professional. 

23andMe’s health risk tests, for example, look for a handful of variations that may or may not increase your risk for developing the disease in question. They are unable to consider lifestyle factors or family history into their results. If you are at a higher risk of certain diseases, a doctor will prescribe much more robust DNA tests and explore the facets of your life that DNA tests can’t access.
Assume the results are static
Companies regularly update their algorithms based on the latest science. If you’ve decided not to delete your DNA data from a given service, logging in every once in a while can provide new information. This is especially true in regards to ancestry, where new connections can be made with each new person who tests their DNA.
Draw hard lines with ethnicity results
There are significant gaps in data that prevent making clear connections between DNA data and certain ethnic groups. The results should point you in the right direction, but not inform what your ethnicity is. For the vast majority of people, a mixture of various ethnicities and places-of-origin can be expected.
Leave your data with the site indefinitely.
Data breaches and leaks occur; your DNA data being leaked may eventually have far worse implications than a breach of your social security number. Each site has steps on how to delete your data. After you download the raw data and explore your genetic analysis, it’s recommended that you remove your data.

What Can You Learn from Your Genes and DNA Tests?

Most people take a DNA test to learn more about their ethnic heritage. A significant portion of test takers are also using tests to learn more about their genetic health risks. There is also a growing number of people using tests to learn more about their genetic predispositions concerning fitness, diet, and lifestyle.

DNA testing offers information with a wide range of uses.

But not all tests are created equally.

Some less-than-scrupulous tests claim to offer predictions about a child’s athletic ability or their potential for learning. Marketing claims include things like help with career profiling or the ability to pinpoint things about your personality. Experts claim these tests do little more than harm consumer confidence in legitimate DNA testing.

Which genetic tests should you take seriously?

The larger, well-known companies including 23andMe and Ancestry are classified as recreational. However, they are reliable and provide professional scientific assessment of test samples. They use data to track patterns and interpret genetic relations.

But some of these companies are forming alliances that experts view as questionable. When a company like 23andMe works with a wellness company that is unregulated, it could lead the industry down a risky path.

There is also concern that people will misuse the legitimate information they have or give it too much weight. For example, if a DNA test tells you about a genetic tendency to be overweight, are you more likely to give up on your efforts to maintain a healthy weight?

Could DNA testing give people an excuse to be less responsible about their health?

This is one of the reasons why people are encouraged to discuss their DNA test results with a doctor. Having a professional interpret your results and help you apply them to lifestyle changes ensures the genetic information revealed through testing is used in the most effective way.

How accurate is the DNA test?

It depends on whether you are talking about ancestry or health accuracy. In either case, there’s no easy answer. Let’s consider this question about accuracy based on your reason for taking a DNA test.

Ancestry Accuracy

DNA testing is great for finding a closely related family member. Most tests can reveal first and second cousins or closer relatives who have taken the same test as you.

But modern-day tests fall short of revealing specific information about your ancestry and ethnicity if it goes beyond close relations. You won’t discover specific locations where your ancestors lived by taking a test but might find out the general region from which they lived.

Health accuracy

For 23andMe to include genetic health reports, it underwent a lengthy FDA approval process. The company had to show its results could be reproduced 99% of the time in clinical labs. 

Unfortunately, not all of the results are not immediately actionable or even understandable. 23andMe offers tutorials before allowing you to see health-related risks and predispositions, but that doesn’t mean you should base important health decisions on your results. 

The best you can do is get general information from your results and discuss them with your doctor.

What are the most popular DNA testing services:

CompanyDatabase SizeSales (est)
Ancestry.com15 million14 million units sold
23andMe10 million5 million
Family Tree DNA1 millionUnknown
MyHeritage DNA2.5 millionUnknown
AfricanAncestry.comUnknownUnknown
Living DNAUnknownUnknown
National Geographic DNAUnknownUnknown
HelixUnknownUnknown

What about DNA Paternity Testing?

One of the first things to come to mind when thinking about DNA testing are issues related to paternity. Genetic testing companies provide information that can be used to determine paternity. However, most of the at-home tests available won’t hold-up in court. 

Anyone interested in using DNA paternity testing should conduct a test as usual. Provide a sample of DNA from the child and the potential father to the genetic testing company. The results should show whether or not and how closely the two are related.

DNA paternity tests provide useful information for families that have questions about paternity.

If you are interested in DNA tests before a baby is born, you’ll need to discuss your options with your doctor. There are tests available that are safe for testing during pregnancy, but you need a safe and effective method for collecting DNA.

What to Know Before Taking a DNA Test

There are several things to keep in mind if you decide to use DNA testing:

  1. Know what the test involves, how you’ll provide a sample, and what you can expect in return.
  2. Understand that DNA testing has a “dark side.” There might be information in your results you never wanted to learn.
  3. Review tips for choosing the best DNA testing service based on your needs.
  4. Understand the limits of DNA testing and how your results can mislead you.
  5. Consider scheduling an appointment with your doctor to review your results if you want to know more about how to use your results to make lifestyle improvements.

Finally, don’t expect perfect accuracy and know that the information you gain from taking a DNA test isn’t failsafe. Be open-minded and curious, but don’t consider your DNA test results canon.


Cheap DNA Kits (all under $60). Read our 2021 Guide.

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