Calling all 23 And Me mavens, and genealogy fans in general.
September 22, 2016 3:06 PM   Subscribe

I don't have the $199 to plunk down on an ancestry test, but one of my siblings certainly has. (We all share the same parents.) If my sister, two years younger than me, springs for the test, will the results be the same for me? Yes, I realize we have different chromosomes. But our european blood mix would be the same between us. Wouldn't it?
posted by BostonTerrier to Science & Nature (11 answers total) 9 users marked this as a favorite
 
But our european blood mix would be the same between us. Wouldn't it?

This was not exactly the case between me and my sibling when we did this a few years ago. We both had the same general mix of ethnicities, but in pretty surprisingly different proportions -- sib, for example, showed 15% Irish while I showed less than 5%. The same was the case for all of my sibling's kids -- same mix, wildly different proportions.
posted by the return of the thin white sock at 3:15 PM on September 22, 2016 [2 favorites]


Do you have $99? (I just heard about this reduced pricing for ancestry-only reporting today.)
posted by kimota at 3:29 PM on September 22, 2016 [2 favorites]


My mom and her sister both did it. Their results vary by about ~15% total. My aunt has slightly more northern European while my mom has more eastern European and Ashkenazi markers (but also has a higher % unassigned; she did it a few years before my aunt, so it's possible they just refined the model since then).

If possible, I highly encourage you to get one or both of your parents to do it. It's cool to see the breakdown of what you inherited from whom and it also helps with figuring out how you're related to the genetic relative matches (if there's a close enough match and you have a few generations of trackable genetic family history). I believe they re-run everyone's DNA after a parent/child match is linked as well, which produces more accurate results. If you're female, linking to a brother or father is the only way to find out your paternal haplogroup.

I'd just go with the ancestry-only plan, if you decide to do it. I signed up before the FDA approval and the new "reports" while interesting are not super enlightening (and you can figure it all out yourself using the raw data anyway -- but verify that they still give you the raw data with the $99 plan). You can upgrade to the health reports at any time as well.
posted by melissasaurus at 3:47 PM on September 22, 2016 [2 favorites]


Not exactly the same. My sister is 61 % Irish while I am 66% Irish. The diffenent groups...Northern European etc were the same just spread out differently.

It's a fun thing to do with different generations in the family as well.

We waited till they had sales for the price to drop and then once a year someone would do it. Maybe you guys can chip in on the tests. We did that on some. Good luck. Have fun.
posted by cairnoflore at 3:50 PM on September 22, 2016 [1 favorite]


The point is, it is just as accurate for you and your sister (assuming you do both actually share parents). Yes as you know there will be differences between you and your siblings, but these are within the random sorting that can be expected (but aren’t really mentioned by the commercial operations). A suggestion that you are more or less Irish based on this test is of course nonsense, you are exactly as Irish as your sibling, the test results reflect the natural variation and highlight how inaccurate they are on the individual level.
posted by wilful at 4:23 PM on September 22, 2016 [9 favorites]


Yes, you have far more genealogical ancestors than you do genetic ones. Think of it this way: If your father is half Irish and half Chinese/Russian, every gene he passes down to his children has a chance to come from his Irish parent or his Chinese/Russian parent. This is a random selection of genes every time your father generates a sperm cell, so theoretically there could be a sperm with 100% traits passed down from his Irish parent, or a sperm with 100% traits passed down from his Chinese/Russian parent, or anywhere in between. Recombination also means that many genes that could be in that sperm ready to be passed down are random combinations of material from both parents.

Here is a more scientific explanation.
posted by chainsofreedom at 4:55 PM on September 22, 2016 [17 favorites]


Hey willful - no raining on my Irish parade. It's one of the only things I can lord over her. But to add the further nonsense - I look very Irish. She does not. We barely look related.

I say have fun with it and don't let the sciency folks spoil the fun.
posted by cairnoflore at 6:29 PM on September 22, 2016 [1 favorite]


But our european blood mix would be the same between us. Wouldn't it?

That's not what 23 and me and similar are even measuring. They're looking at some of your polymorphisms and saying 'well this one is over-represented in population x so we'll assign it there' (and the first half of that sentence has real issues as it is) and so on through them all, then totaling up the amounts. Then it's left to you to assume the direct ancestry link. So it classifies the genetic diversity you have now, not measures your bloodline or whatever. Using a pretty loose classification. And since you have on average about 50% of the same gene variant inheritance as your sibling you can clearly have different, even quite different, results.

It will give a broad picture that is correct. Mine, for example, would be guarenteed to have a bunch of different western European markers as the majority proportions just because that's what all my great-grandparents are. And that fact is unlikely to change between my siblings and I. But if our parents came from very different parts of the world then who knows? And the smaller details than that will differ between siblings, but they aren't meaningful anyway. Both because of what the test is actually testing and because race is a largely social construct rather than a biological one.

From a biological point of view, these genetic ancestry tests are largely a scam. So read it however you want, it's all as equally inaccurate.
posted by shelleycat at 9:29 PM on September 22, 2016 [11 favorites]


Not necessarily. Let's say, for example that your father, has 10% DNA from the Iberian peninsula and your mother has none. While you and your sister both got 50% of your DNA from your father, but it was a random 50%, not half of each ethnicity in his DNA. So, you might have gotten almost all of his Iberian peninsula DNA while your sister got none.
posted by hworth at 10:57 PM on September 22, 2016 [1 favorite]


Mostly, but not necessarily. I did 23andMe when they had a $99 special. My brother took the test, as well as ordered a kit for our dad and maternal uncle before they passed away. My brother had some ancestry results that did not show up for me.

Our dad was South Asian - I'm 49.8% vs. my brother's 48.0%. My brother also had some small amounts of East Asian ancestry show up (which we can see via our dad's profile), which did not show up for me at all.

Our mom was Italian - on that side we both have mostly Southern European, mostly Italian - but the percentages are different. But my brother's profile shows findings of small amounts of Northern and Eastern European ancestry - those do not show up at all for me.

"Middle Eastern & North African" also showed up for both of us - but it's my 1.9% vs 4.4% for my brother.

It's interesting to see and compare, especially to see how the chips fell via the previous generation. But I'd take it all with a grain of salt, too.
posted by raztaj at 4:28 AM on September 23, 2016 [1 favorite]


If what you're interested in is genealogical ancestry, then your full sibling's genetic markers are exactly as informative as your own genetic markers. But, as others have said, you and your sibling very likely have some variations in which genetic markers you carry, which will cause 23andMe or other genetic ancestry services to report different estimates for you. In this case, both sets of genetic markers are equally accurate for both you and your sibling, and the amount by which they result in different estimates reflects the accuracy of the estimate. In principle, pooling information from both you and your sibling should give you a more accurate estimate for your (shared) ancestry. 23andMe allows you to link accounts with family members, so they may be able to do something like this, but I don't know for sure.

Short version, if your sister takes the test, the results will be exactly as accurate for your genealogical ancestry as if you took the test, and vice versa, even though your test results may not be identical.
posted by biogeo at 8:08 PM on September 23, 2016


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