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

By the end of 2006, DNA testing had dropped to about $14 million but remained mostly inaccessible to even the well-connected. Today, a full sequence might cost you around $1000, but consumer kits - convenient at-home DNA testing - can be had for only $70 to $200.

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What is DNA?

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 living human cell contains a special compartment known as the nucleus - often called the ‘brain of the cell’ - that contains and protects our DNA. From here, instructions are transcribed from your DNA blueprint that dictate the actions, development, and growth of your cells. The entire sequence of your DNA is unique - barring identical twins - but all the discrete parts, or genes, were inherited in roughly equal measure from your parents - 50% each. 

This inheritance is the basis of genetics and the reason why some diseases or traits are found throughout family lines. It also forms the foundation of DNA testing for ancestry - some ‘markers’ found within your DNA can be traced backward, through your father- and mother-lines, for thousands of years. These lineages are kept separate: 

  • Genetic males are defined by their inheritance of a Y-chromosome, received from the father. Males have a Y-chromosome that is mostly the same as their grandfathers’
  • All humans receive a specific subset of DNA - mitochondrial (mtDNA) - only from the mother. While this particular DNA has little impact on traits, it is used to create matrilineal lines

This situation means that anyone can test their motherlines through mitochondrial DNA testing, but only genetic males can have their fatherlines analyzed. However, markers in the other 44 chromosomes - or autosomal DNA - can be used to construct ancestry estimates for at least five generations. With this in mind, make sure you understand what you want to find when you test your DNA for ancestry:

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

Who should undergo a DNA test?

DNA testing is suitable for anyone who wants a better view of their health and how their DNA affects it, as well as examining their ancestry and the construction of family trees. However, make sure you’re familiar with the pros and cons of genetic testing and what genetic testing may reveal. One can discover - through DNA testing - health conditions they carry or are predisposed to, learn or confirm paternity, suggestions on how to best build muscle, and even sleep trends. 

While the industry is still in its infancy - along with the research that underpins it - some information is better than none when it comes to genetic testing. Cheap, consumer DNA testing gives you a wealth of medical knowledge and a blueprint of you, something that will only become more valuable as time goes on.

If you are prone to hypochondria or anxiety, taking a DNA test might not be for you, or may be best guided by a medical professional. This is a process that is supposed to be fun, informative, and enjoyable and not promote excess worry. The best way to ensure a positive experience is to educate yourself thoroughly before you begin.

How to do a DNA test?

Every at-home DNA test is different in their own ways, but each follows the same general premise:

How to Take an At-Home DNA test

  1. Order

    The first step is ordering the testing kit from whatever site you’ve decided to use. Use our reviews to explore the strengths and weaknesses of each test.

  2. Receive the collection kit

    Next, you will receive a saliva collection kit (either a spit tube or a cheek swab) and instructions for providing your DNA sample (registering your kit, etc.). Saliva contains skin cells which, like all human cells, contain DNA suitable for analysis.

  3. The DNA lab receives and processes your sample of DNA

    Roughly 99.5% of human DNA is identical from person to person. However, there are little differences - known as variations or mutations - that make each individual unique. The lab extracts DNA from the cells contained in your sample, then processes the DNA to scan hundreds of thousands of variations throughout your genome.

  4. Analyze

    Finally, your DNA data is examined, and personalized genetic test results are created according to well-established medical and scientific research. Further, your DNA can be compared to other people in the company’s database to see if you share enough matching variations to suggest a blood relationship.

Once you get your DNA data -

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Do:

Protect your data
First, every service should provide information on how your data will be protected. Review what is going to be done with your DNA data, who it might be shared with, and how you can control it. Your DNA is a blueprint of you and may provide unprecedented information to those who have access. If you’d like to be very cautious, you can delete your data entirely from the service’s database – make sure to download your raw DNA data first.
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
Other services may process your data in different ways than the company that collected and initially analyzed your DNA. This is an easy way to check your results against other databases and research – effectively a second opinion – and to see the similarities and differences. Keep in mind that you are exposing your DNA data to more parties; ensure that the service is trustworthy and offers the option to delete your data afterward.
If you’ve opted for health-related analysis, explore your outcomes
Genetic testing for health can provide information on risks and predispositions; however, they’re no reason to worry, even with dire predictions. DNA testing for health risks is still a science that’s in its infancy. Experts still don’t precisely understand what variations or mutations could cause different diseases, traits, or risks. At-home testing is not meant to be diagnostic, and all results should be taken with a grain of salt until verified by a medical professional. Do not use things such as a reduced risk for breast cancer to skip mammograms; likewise, a predisposition to cardiovascular disease doesn’t mean you need to say goodbye to sodium.
Review your shared matches
Each service has a different approach to genetic matches, but most offer the option to explore individuals that share enough DNA variations to assume you’re related. This can be used to confirm suspected relations or explore your family tree in ways that paper records can’t match. While it is exceedingly rare, be ready to find long-lost relatives, notable ancestors, or maybe even to change the entire concept of your family history.
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Don't:

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.

How accurate is the DNA test?

This is a complicated question without an easy answer; we devoted an article entirely to the topic. In short, it’s easier to answer this if Ancestry and Health aspects of DNA testing are separated, as they rely on different foundations to power their accuracy.

Ancestry Accuracy

DNA testing is very good at finding closely related family members, exemplified by its frequent use in forensic science and law enforcement. It’s fully expected that you will find any 1st or 2nd cousins - and other relatives that might be equally removed - that have taken the same test. Unfortunately, they are not nearly as accurate when determining your ancestry and ethnicity, much less the specific locations where your ancestors lived. In this regard, the services are merely comparing your DNA to those with confirmed and documented ancestry. The general regions will most likely be correct, but the specific countries might not be exactly perfect.

Health accuracy

For 23andMe to include genetic health reports, it had to undergo a lengthy FDA approval process to demonstrate that their results could be reproduced 99% of the time in clinical labs. However, to avoid the sticky issue of ethical concerns and informed consent, most of the results are of a generally lower impact than what could be conveyed.

While the accuracy of the reports isn’t an issue per se, many results are not immediately actionable or even understandable. 23andMe tries to head this off at the pass by making you complete tutorials before it allows you to see health-related risks and predispositions, but the problem can still occur.

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
Joel is a writer with a passion for the science of DNA and the power of its manipulation.

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