How do DNA tests work? What you need to know

Written by Lewis Cuthbertson, PhD | Last updated:

The term home DNA test is used a lot nowadays, but what does it mean when you say at-home DNA tests? The truth is only one step is performed at home – your sample collection. So, how do DNA tests work, and what you can find out from them? Read on to learn more.

What is home DNA testing?

Whilst the term home DNA test might suggest the entire test is carried out at home, actually, only the sample collection part is. When you purchase an at-home DNA test, you’ll receive a collection kit at home, either for a saliva sample or a cheek swab.

But then, how do DNA tests work after you provided your sample? Once you’ve collected your sample, you then mail it to the DNA lab nominated by your testing service and the rest is done for you by highly trained professionals. Most of the time, your results are sent to you through an online platform, email, or mail, and you can view them from your home.

How to take a DNA test at home

You’re probably wondering how to do a DNA test at home, but actually at home DNA tests are pretty simple. If you buy the test from a reputable company, it will likely come with easy to follow step by step instructions to perform the test optimally.

How do DNA tests work

DNA Test Kit

In general, you can’t go wrong if you read the instructions thoroughly prior to generating your sample. The most common kits emphasize that you shouldn’t eat or drink beforehand, and that the best time to collect a sample, if it is for a saliva or cheek swab test, is in the morning prior to brushing your teeth.

Most DNA tests come sealed to avoid contamination with anyone else’s DNA, so it’s important that you don’t unseal your collection vessel until you’re ready to provide your sample.

How does a home DNA test work?

So you’ve provided your saliva sample, what next? How do DNA tests work?

The first step is to extract your DNA from the saliva sample. Your DNA is then copied up to several million times to generate enough DNA to be genotyped.

What is a genotype?

Your genotype is your own personal DNA sequence, so genotyping is reading your DNA sequence. This process is carried out by a machine which is 99% accurate. Your genotype is very similar to every other person on earth, barring some important differences that make you unique. These are called genetic variants, and it is these variants that are used by companies like 23andMe or Ancestry.com to identify your heritage or health traits.

How does genotyping work

As mentioned, genotyping is performed by a machine. Once your DNA has been copied or amplified, it is cut into smaller pieces and loaded onto a small glass DNA chip called a microarray. This small glass chip has millions of invisible to the naked eye extensions all over it which stick to your chopped up DNA. This chip is inserted into the machine which uses fluorescence to read the sequences of the DNA fragments attached to the chip.

Our DNA is made up of four bases, which can simply be thought of as the letters ACGT. These letters are combined in different sequences which act as the blueprints for all living things. The genotyping chip is used to read your sequence of ACGTs and identify any variations in known sequences that can be used to provide an insight into your ancestry or health traits.

How do DNA tests work for ancestry?

DNA tests trace your ancestry by using a reference database. Ancestry.com has the most user generated ancestry data followed by 23andMe. In simple terms, your genotype is compared to the genotypes in the reference database to see which ethnicities of DNA yours is most similar to.

How do DNA tests work for ancestry

An ancestry report

The best way to provide the most accurate ancestry information is by comparing genotype to as many other genotypes as possible from around the world. This is why it’s best to choose a company with a large database if you’re interested in the most accurate representation of your heritage.

How do home DNA tests work to identify health traits?

DNA health tests identify whether you carry genetic variants which have been linked to a disease or particular health trait. If you know you are predisposed to a particular health condition, you can take action to lower your risk of developing it in order to optimize your health and live a happy and healthy life.

Companies scan your genotype to identify whether you carry any known genetic variants or SNPs which have been associated with a particular health trait or condition based on scientific studies. Any reputable company will offer you a direct link to the studies they have used to analyze your risk for a particular condition.

What you must always bear in mind is that whilst your genes can increase or decrease your risk of certain health conditions, whether or not your predispositions come to fruition is largely dependent on environmental factors like your diet or lifestyle. This is why it’s important to know your DNA so you can make targeted changes to counteract the negative effects of your genes.

How to choose the best DNA health testing company

Understanding your genetic risk is undoubtedly useful for anyone, as it can help to guide your life choices. All companies that offer genetic health testing including 23andMe or SelfDecode have different pros and cons which you should understand prior to selecting a company.

If you would like a simplistic insight into your health and are not interested in optimizing your health based on your genetics, then most services will be suitable. Most companies limit their analysis to telling you whether you’re likely to develop certain traits. However, if your goal is to reduce your risk of developing negative health conditions then you may want to look at a service like SelfDecode.

Unlike other services which mostly provide generic advice not tailored to your genetic needs, SelfDecode goes a step beyond merely highlighting your genetic risks by offering personalized health recommendations which are scientifically proven to improve the environment your genes function in.

How do DNA tests work for health

Unlike other companies that analyze only one or two variants to determine your genetic risks, SelfDecode uses predictive algorithms to analyze up to 85 million genetic variants (~1 million per wellness report), giving you the most accurate health data based on your genetics.

Takeaway: How do DNA tests work?

In this article, we explained how DNA tests work. So if you were wondering how to test DNA at home, you should now understand that the term home DNA testing is actually slightly inaccurate, and that all you do at home is provide a sample. The rest of the DNA test is more complex and performed by professionals in a laboratory. The part of the process that is most important to you, the consumer, is deciding which DNA testing service is best suited to your needs.

If you’re interested in finding out more about your heritage, then using a service like Ancestry.com or 23andMe could be your best option as these companies have the largest customer databases allowing them to provide you with the most accurate insights into your ancestry.

If health is what you’re interested in, then whilst most genetic wellness reports can provide you with limited insight into your health predispositions, you really should look for a more complete service like SelfDecode.

SelfDecode not only gives you the most detailed and accurate information about your health, but also provides you with personalized recommendations to counteract any negative health predispositions you may have based on an analysis of up to 83 million genetic variants.


About the Author

Lewis Cuthbertson

Lewis completed his PhD in Molecular Microbiology at Northumbria University (UK). Lewis spent several years researching the biodiversity of bacterial communities in the Arctic and Antarctic, whilst also performing research for a DNA sequencing service, where he was involved in several health based microbiome studies. This gave him an insight into how the highly diverse and invisible to the naked eye portion of human health, can potentially impact an individual’s quality of life, driving his desire to help others understand their own complex health needs through the most current scientific research.


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