Previous: Traffic is Terrible and Terrible for You
Next: Empowering Pharmacists to Address Excess Medications



View count:28,119
Last sync:2024-01-31 22:30
Mail-in DNA tests have been in the news recently. Test results can be over the map, with even identical twins getting some widely variable results. What's the deal with that?

The Vox article:

Subscribe to Healthcare Triage!

Aaron has a book out now! It’s called The Bad Food Bible: How and Why to Eat Sinfully. You can order a copy now!!!

Amazon -
Barnes & Noble -
Indiebound -
iBooks -
Google -
Kobo -
Any local bookstore you might frequent. You can ask for the book by name or ISBN 978-0544952560

John Green -- Executive Producer
Stan Muller -- Director, Producer
Aaron Carroll -- Writer
Mark Olsen – Graphics
Meredith Danko – Social Media

And the housekeeping:

1) You can support Healthcare Triage on Patreon: Every little bit helps make the show better!
2) Check out our Facebook page:
3) We still have merchandise available at

So, there's been some news recently how identical twins can send their DNA to companies, like 23andMe, and receive different results. How can that be? Brian Resnick at Vox summarized how this could happen, and it was interesting enough to bring it to you. So, while I think you should go read his original work (link down below), I also want to summarize some of the high points here. This is Healthcare Triage News.


Let's start with the fact that identical twins should have identical DNA. That's the whole point. They originated from the same fertilized egg. They're identical.

Some journalists showed that twins often get different results, even when their data is sent to the same company. This isn't even a company-to-company difference. In their story, they told of one twin who was told she was 13% broadly European compared to another who was only 3% broadly European. They did this at five different companies, and they got different answers from each.

I should note that I had my DNA checked by They basically reported "dude, Eastern European Jews. Stop bothering us." I'm not kidding. Here's the pic. More than 99% of me is from here. They conceded that maybe, possibly less than 1% of me comes from Sweden, but likely in a large circle that also includes Eastern European Jews. Since I already knew I was of Eastern European Jewish decent, I don't feel like I learned a lot.

Anyway, how can you get different results? First of all, they don't test all the DNA. We humans have like 99.9% of that in common. They only look at the parts where people might be different. They isolate those areas, replicate them a lot so they're easier to measure, and then compare those to known genes from certain geographic areas. But, those replication processes aren't perfect; they're good, but they're not perfect. They make a mistake like 0.1% of the time. Unfortunately, when you're processing like a million locations on a gene, that means 1,000 mistakes. Those mistakes make it so even identical twins can get different results.

Plus, they have to match those genetic bits of you and me to a database of genetic bits they think are from certain areas of the world. There's not one database for that. Each of the companies has their own, so different companies might get different results.

And, it's not like an easy match-them-up process. There's a computer program that makes a best guess. When different countries have similar genetics, like England and Ireland, for example, the computer might sway one way or the other based on small difference. Except for me; fully Eastern European Jewish. No doubt. Lock it in.

So, when you're using one of those services, bare in mind their guesses are full of imperfections. No one has a lock on the truth. They're telling you only about genetics, not about where people come from. They're also only telling you about the DNA you inherited, not everyone you're related to. They're full of gaps. Act accordingly.


Hey, do you like the show? It really helps if you like the video, and really if you subscribe right down there.

And, another good way to support the show is at Go to We'd really like to thank our research associate, Joe Sevits, and our surgeon admiral, Sam.

And if you love Healthcare Triage content, get even more at the Healthcare Triage Podcast. It's great! Get it at iTunes or Spotify, or wherever you download your podcast content.