Genealogy – How Does It Work?
- Info Test ADN
- Apr 7
- 3 min read
Updated: 3 days ago
I'm pretty sure you've already seen people opening their results and being completely stunned, totally shocked. So I thought I would also take a test to try to explain how it works. Because honestly, it’s incredibly mysterious—how is it that these companies can really offer to reveal our ethnic origins through percentages tied to geographic areas?
How do you take an ancestry test?
It’s a self-administered test with small boxes, cotton swabs, a completely sealed plastic bag—in short, just a simple swab inside the mouth to collect cells that contain our DNA.
So there you have it. Once you have the sample, you place this little cotton swab inside a small vial, pack everything in your plastic envelope, which goes inside another paper envelope, to send it all to the designated laboratory.
But then, how do they analyze it?
That’s what interests me most, because I don’t really think I have the tools to fully understand how it works, especially how to properly interpret the results, because that’s the most important part. I think a lot of people don’t necessarily understand all the nuances that can be drawn from it.
Several weeks later, I received the results of a DNA test with conclusions that seem quite surprising…
The information is tied to geographic zones, mainly in Europe, but absolutely nothing in France. When I give my DNA to a company conducting very precise genetic analysis, I expect to get a result showing 75% from France. Then of course, I expect to see small bits from here and there, like Spain or Belgium, because that’s usually what you see in the results of other participants.
But in my case, the result shows 0% from France. So how do they do this? They take your DNA data and compare it with other individuals. But more importantly, beforehand,
They create groups of what are called reference populations.
When they create the 42 reference population groups, what they’re interested in is not identifying individuals, but rather families in which the current individuals, their parents, and grandparents all come from and live in the same geographic region.
So that across two generations, their biological heritage serves as a reference for the genetic makeup of that region. Depending on the laboratory, they have several groups distributed all over the world. And technically, what happens is that your percentage in the results is a percentage of similarity compared to these reference populations. What we can say is that, according to this lab, my DNA composition is closer to the reference families from the United Kingdom than to those from France.
The interesting thing is that there’s a research project aiming to advance discoveries in DNA, so taking part in this ancestry test also allows them to obtain increasingly precise results in estimating population origins.
It’s therefore very likely that the results will evolve over time.
The raw data
It’s possible to download all the DNA data. The genetic data file contains the raw data produced by the lab from your sample. Scientists used seven hundred thousand locations in the DNA, within the entire genome which is made up of three billion base pairs. So, seven hundred thousand locations of your DNA were sequenced.
There’s no need to sequence the entire DNA, because among the three billion letters that make up your genetic information spread across the 23 chromosomes, there are many letters that are identical among all humans. What interests laboratories are the differences between individuals—and even more, the similarities within populations.
That’s why they use the system of genetic markers, because they can be compared.
The scientific procedure
During the analysis procedure, the laboratory uses a machine to extract the DNA from the samples. In this first step, the cells are broken open to extract the DNA. Then they use DNA microarrays, which are surfaces where DNA probes corresponding to the genetic markers they want to identify have been deposited.
They then use chemical baths so that your DNA, which has been broken into many small fragments, naturally binds and sticks to the specific locations corresponding to those markers on the DNA chip. By using millions of tiny DNA fragments that match all the identifiable possibilities, they create what is called hybridization between the DNA fragments. Hybridization is the complementarity of two DNA strands.
A laser then reveals all the places where your DNA has matched the reference DNA. What’s important is that the analysis of the results only allows for an estimation of your origins based on the similarities already present in their database. This is how, today, it is possible for you to know the origin of your family.
