July 26, 2019
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Before you Buy: Everything You Should Know About Personal DNA Analysis

A detailed look at personal DNA analysis, what it measures, what you can find, and a rundown of different companies you can use.
Tomohiro Takano

What You Need To Know About Personal DNA Analysis

Personal DNA testing is a new and exciting way to learn more about yourself and your genetic data. Order a kit, spit in a tube or swab your cheek, and mail the sample back. That’s all that will be required of you. But, before you jump in, there are some very important things to understand about personal DNA testing. You may want to consider several of the following issues before you jump into consumer genetic testing.

What do Personal DNA Tests Actually Measure?

The term ‘personal DNA analysis’ is actually a bit misleading. When the major DNA testing companies test your DNA, they are usually not testing the whole molecule. Most companies are also not testing your exome, which represents all of the protein-producing genes in your DNA. What the testing kits are looking at is individual parts of DNA, which have been found to have some significance on health traits or which can be matched to reference populations in ancestry testing. 

Your DNA molecule is made of units called nucleotides. These nucleotides form connections with each other and form DNA molecules which are billions of nucleotides long. In fact, you have around this many nucleotides in your genetic code:


While your DNA is unique to you, you share 99.9% of the same nucleotides as every other person on earth. So, instead of testing all of these nucleotides, DNA testing companies focus on single nucleotide polymorphisms, or SNPs (‘snips’). These nucleotides are known to be variable within the human genome, and many SNPs have been correlated with various conditions. As such, most DNA testing companies test less than a million SNPs. 

What Can Personal DNA Testing Tell You?

Health Traits

SNPs have been correlated with certain conditions, including several diseases and disorders. However, users should note the difference between correlation and causation. A correlation simply says that various research has found a connection between a SNP and a disease. 

Causation, on the other hand, would mean that a specific SNP is actually responsible for a disease. For instance, the disease cystic fibrosis is actually caused by changes in the DNA which cause a cell membrane protein to fail. This stops cells from functioning normally, leading to the symptoms of cystic fibrosis. Tests that search for these genetic variants are called carrier status tests.

Unfortunately, most of the diseases and ‘health risks’ in DNA results are only correlations and do not actually describe causation. This means that certain genetic variants are more likely to be found in people with specific diseases, but scientists do not yet know if the genes cause the disease, or if they were simply found more often by chance. 

So, while your results may say that you have an increased chance of Alzheimer’s disease, researchers actually may have little idea how these genes impact your brain cells. While these types of results can be interesting, you should seek a genetic counselor to understand exactly how the results of a DNA test kit can affect you.

Ancestry Testing

When it comes to ancestry testing, the results are a little more straight-forward. Ancestry testing relies on matching segments of your DNA with those of reference populations. Reference populations are groups of people who have lived in an area for a long time. Since our DNA is inherited, or passed down from our parents, the large majority of genetic changes in your DNA come from a parental source. 

Your parents got their DNA from your grandparents, and so-on, all the way back to the dawn of human history. By analyzing which segments of your DNA match various reference populations, a DNA testing company can analyze approximately where your genes came from. Most companies will give you a breakdown of your heritage in the form of an ‘ethnicity estimate’. 

These reports get more accurate with larger reference populations and larger DNA databases. So, if you are interested in ancestry testing you should select one of the bigger companies. This will give you the most accurate view of where your DNA came from. Some can test whether or not you have sequences of Neanderthal DNA, African DNA, British DNA, East Asian DNA, or any sequences from a number of other regions, depending on the company.

What Companies Offer DNA Tests?

Below are several of the most popular DNA testing companies, along with short descriptions of what the companies offer. Check them out!


- One of the first and largest DNA companies. Offer both ancestry testing and health information related to your personal genetic profile.


- Provides ancestry testing. Has the world’s largest North American historical records database to help find family members and build a family tree.


- Ancestry testing, which looks at 3 kinds of DNA to show your ethnicity estimate, as well as your maternal and paternal line haplogroups, which trace your roots back to the dawn of humanity using Y-chromosome DNA and mitochondrial DNA.


- Known mostly for their consumer DNA paternity tests sold in pharmacies, the company now offers analysis for health and ancestry traits. 


- A company like Ancestry, only based in Europe. Can provide ancestry testing as well as a huge European historical records database. 


- An ancestry DNA testing service. However, the name is slightly misleading because the company does not offer the ability to build a family tree.

Which Company is the Best and Most Accurate?

If you are trying to decide which genetic testing company is most accurate, you will likely hit a dead end. In general, most companies use the exact same technology, the same DNA testing chips from the company Illumina, and very similar methodologies. While the process and exact methods may differ slightly between each company, they are all very accurate when it comes to your genetic information and measuring SNPs.

When it comes to your family history, most of the companies will provide very similar results. However, differences in test results do occur because each company uses its own reference populations when analyzing a DNA sample. So, for the most accurate ancestry tests, you should look to the big companies like Ancestry.com and MyHeritage, because they have the largest reference populations. 

Can You Do Anything Else With Your Personal DNA Data?

Several companies offer you the ability to download a raw DNA data file. With this file, you can use a number of free services and 3rd party testing services to get more insights into your DNA. To find out more DNA upload sites, check out our article "The Best DNA Upload Sites"

Tomohiro Takano
Tomohiro Takano
Co-Founder and CEO