• Emily Poulin

The Story in Our DNA: How Does 23andMe Work?

Updated: Jul 25, 2019


Who am I?

Where in the world do I come from?

What is my ancestry?

Questions about our history and family history are all tied to our identities.

And the answers to these questions can be found in our DNA.



Now that the holidays are around the corner, you've probably seen or heard advertisements for DNA-based ancestry services like 23andMe and AncestryDNA. In fact, it may make a great gift idea.

Just send in a vial of saliva and voilà! Your ancestry awaits.

But how does it work? How can a company know so much about our ancestry using only our spit?


When you send your spit to these companies, you're really sending your DNA from the cells found inside your mouth. Scientists at these companies receive your spit sample, isolate these cells, and break them apart. This releases the DNA, which can then be isolated and analyzed.

What are they looking for?

According to 23andMe, over 99% of our DNA is identical. It is that small percentage that is not that defines how we are different from one another. This 1% or so of non-identical DNA can be variable and can be identified using single nucleotide polymorphisms.

Single nucleo-what?

Single nucleotide polymorphisms, or SNPs (pronounced "snips") are single letter changes in a DNA sequence. Remember, four letters (A, C, T, and G) make up our entire DNA code. A SNP occurs when, for example, A is present instead of C.

These variations are what DNA ancestry tests look for.

SNPs are passed down from generation to generation - we receive 50% of our DNA from each of our parents and if this DNA contains a SNP, it will also be present in our DNA.

Many SNPs are associated with a geographical region; thus, people whose ancestry is derived from a certain region are more likely to contain SNPs associated with that region in their DNA. DNA ancestry companies have databases that contain hundreds of SNPs and their geographical associations. They compare your SNPs with those in the database and based on the results, they are able to determine the likelihood you are from a given region.

What about my siblings? Will we have the same ancestry results?

Here's the cool thing: maybe not.

Here's why. Each one of us gets half our DNA from each of our parents. But if you have siblings, these halves are different (if they were the same, all siblings would be twins).

Each sibling gets a random assortment of each of their parents' DNA, and if your random DNA assortment contains different ancestry-associated SNPs than that of your sibling, your results will be different!

So whether or not an ancestry test is on your holiday gift list this year, know that the keys to your ancestry are in your DNA should you care to spit them out.

Have any questions about DNA and how it works? Get in touch with us and we can cover these subjects in upcoming blog posts!


#SNPs #Ancestry #DNA #23andMe

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