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Genealogy - How does it work?

Updated: Mar 26

I'm pretty sure you've seen people who open up with results and remain totally stunned, totally shocked, anyway I thought I'd also do a test to try to explain how it works. Because it's true that it's super mysterious casually, how come these companies can really offer us to discover our ethnic origins through percentages of geographical areas?

How to do the origins test?

It's a test to do myself with small boxes, cotton swabs, a completely sealed plastic bag, in short with a simple rubbing inside the mouth to collect cells that contain our DNA.

So here it is, once you have the sample, you put this little cotton swab inside a small vial to package everything in your plastic envelope inside another paper envelope to send everything to the laboratory concerned.

But then how do they do the analyses?

That's what interests me the most, because I don't think I really have the tools to fully understand how it works and above all, how to properly analyze its results because that's what's most important. I think a lot of people don't necessarily understand all the intricacies of it.

Several weeks later, I received the results of a DNA test with conclusions that seem quite surprising to me...

The information is linked to geographical areas, mainly in Europe, but absolutely nothing in France. When I give my DNA to a company that does a very precise genetic analysis, I tell myself that I'm going to have a result of 75% in France, then it's obvious that there are going to be little things right and left, like in Spain, in Belgium because it is often like that in the return of the other participants.

But in my case, what comes out is 0% in France. How then do they do that? They take your DNA data and compare it with other individuals. But especially upstream,

They will form so-called reference population groups.

When they make the 42 groups of reference populations, what interests them is to identify not individuals, but rather families in which current individuals, their parents and their grandparents all come from and live in the same geographic region.

So that over the two generations, their biological heritage serves as a reference for the genetic heritage of the region. According to the lab, they have several groups spread all over the world and technically what happens is that your percentage on the results, it is a percentage of similarities compared to the reference populations. What we can say is that according to this laboratory the composition of my DNA is closer to the reference families who come from the United Kingdom rather than that from France. The interesting thing is that there is a research project that is intended to advance the discoveries on DNA and therefore to participate in this test on the origins is also to allow them to have results of more more accurate in population estimates.

It is therefore very possible that the results will change over time.

Raw data

It is possible to download all DNA data, the DNA data file includes the raw data produced by the laboratory from your sample. the scientists used seven hundred thousand places in the DNA, in the complete genome which is composed of three billion base pairs. So there are seven hundred thousand places in your DNA that have been sequenced.

There is no need to sequence all the DNA, because out of the three billion letters that make up your genetic information which is distributed in the 23 chromosomes, there are a lot of letters that are identical between all humans. What interests laboratories is what is different between individuals and even more interesting what is similar between populations. This is why they use genetic marker systems, because they can be compared.

The scientific procedure

During the analysis procedure, the laboratory uses a machine to extract DNA from the samples. In this first step, the cells will be broken up for DNA extraction. Then they use DNA chips, these are supports on which DNA hooks have been deposited and corresponding to the genetic marker they want to identify.

They then use baths to make your DNA that has been broken into many small pieces, naturally join and stick to specific places corresponding to their markers in the DNA chip. It is by using millions of small DNA fragments that correspond to all the identifiable possibilities to thus create a hybridization between the DNA pieces. A hybridization is a complementarity of two strands of DNA.

It is a laser that will then reveal all the places or your DNA that matched with the reference DNA. What is important is the analysis of the results which only allows to have an estimate of its origins according to the similarities that they already have in their databases. This is how today it is possible for you to know the origin of your family.


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