If you've tested with multiple companies, one of the things
that you've inevitably come across is that you have some
matches that are on both databases. And what you might
see is that the amount of DNA that they share is different.
Now, it's not necessarily vastly different. Although
sometimes it is. But it is a little different. So, today,
I'm going to go over what this looks like and some of the
reasons of why this may happen. We test with different
companies and we get different amounts of shared DNA. So,
let's with an example from my family. Now, I'm going to use
my dad and his siblings because I have several of them. And
we've put their DNA on lots of different websites. And so,
we're going to look at this match named John. And the reason
why I picked him is one because he actually shares a sizable
amount of DNA with these people. I know the exact
relationship. And he's also of course on multiple websites.
So, John shares 68 centimorgans with Gloria, 65 with Russ 145
with Scott, and 75 with Marla when we're looking on Ancestry.
Now we take the same DNA. This is what's interesting is this
is the same kit over to GEDmatch. And Gloria she shares 66.1.
Russ shares 84.5. Scott shares 126.9, and Molly shares
66.1. Those numbers are different. If we take a look at
the percentages, we can see that those percentage is actually a
little bit all over. The high is a 30% difference and Russ
has more on GEDmatch than what Ancestry has. The low is Gloria.
she only has about a 2.8% difference between Ancestry and
GEDmatch. But then Scott and Marla have more than a 10%
difference as far as the amount of shared DNA. Now if we were
looking at small matches, let's say 10 centimorgans or 20
centimorgans, then you could easily have some matches that
may show up on Ancestry that when you go over to GEDmatch
they don't show up at all. It's zero or it might be doubled
instead of 10 centimorgans it's 20 centimorgans or 25
centimorgans. So, when you get to smaller matches, these
percentages differences can be quite different. Let's look at
another example. This is Randy and this is going to MyHeritage
instead of Ancestry. Gloria has 50, Russ has 77,
Scott has 137, Marla has 118, and Mary Ann has 127. But when
we look on GEDmatch, we see Gloria has 34, Russ has 0.
Remember, I just said that with small matches, we might go down
to zero but this is one that says zero at 77. And Scott has
133, Marla's 125, and Mary Ann 120. So we look at the
percentages. And of course the high is 100% difference when my
dad because he goes from 77-0. But even Gloria has a 30%
difference in the amount of shared DNA between these two
websites. While the other three are within 10% of what you
would be expecting. I'm going to look at something even
different which is Ivy. And that is Randy's daughter. And so
there's something that we want to be looking out for here.
First off, on MyHeritage, Gloria shares 18, Russ is 52,
Scott's 51, Marla's 43, Mary Ann is 52. But when we go to
GEDmatch, Gloria goes to 0. Russ is at 72. Which is curious
because Russ was at 0 with Randy. So there must be
something error wise going on here. Because Randy gave his
DNA to his daughter. so it's impossible for Russ to match
Ivy and not match Randy. Now you may say, "Well, what about through
Ivy's mother?" Well, it could be through Ivy's mother except
that we've checked that and they are not related as far
distant as we can go out- seven or eight generations. So
the fact that if Ivy was sharing 72 centimorgans with
Russ. And 0. Russ was sharing 0 with Randy is just impossible.
Particularly when we look at Russ's siblings that all share
DNA with Randy and Ivy. So Scott shares 56, Marla 49, and Mary Ann
59. And we look at these percentages. And again we have a
few of these that are centered right around 10% difference.
But there's one of these outliers it's 36% and another
one that is 100%. It goes from 18 to 0 in this case. Alright.
So, why is this happening? Why can't all these companies get
the right answer all the time? That's why you came to this
video. Reason number one, there's always going to be
multiple reasons. Each one of these companies is using a
different SNP set. Even GEDmatch which is not testing,
they are only looking at a specific set of SNPs. And
depending on what test you're using to upload to GEDmatch,
you may have more or less SNPs in your overall set because of
what they're looking at. Now, since we're looking at
different SNPs sets, where we say a match starts and ends is
going to be different for each company. Because that SNP maybe
closer to the actual recombination point or further
away from that actual recombination point. Likewise,
some of the SNPs that might actually be different might be
missing. In which case you might have a place where there's a
bigger segment but really should have been broken up into
two segments because of some SNPs that are missing in that
point. So, that's reason number one. Now, reason number two,
each one of these companies uses a different algorithm in
order to calculate where these matches are. How many SNPs
they need and where the different parts of this is? So,
with matching other people, the algorithm is usually pretty
simple but it is still remember we saw that one case where my
dad didn't match anything on GEDmatch with Randy but he
matched on MyHeritage. But then when we go to his daughter my
dad matches his daughter. So there's something missing there
and that probably has to do with the algorithm of how it's
calculating what that match is. Reason number three. And this is
what really feeds into the algorithm is what criteria are
we using? With GEDmatch you can actually see and you can change the
criteria you're looking at matching. So for instance, how many SNPs do
we have to have to make it a match? Is it 200? Does it have to
be 500 to call it a match? What is the minimum centimorgans to
be able to make that a match? How many SNPs have to be in
between a no match and the next no match to call that whole
thing a no match? So there's several different criteria that
have to go into that algorithm to then tell where these
matches are. So that is why all of these companies, even with
the same people, even with the same test. If you just took the
Ancestry test and upload it to everybody. And look you'd still
see differences in the amount of shared centimorgan matches.
Which leads us really then to the ultimate lesson we should
learn from this. And two things. First off, test everyone you can
see here the fact that I had multiple siblings that are from
the same family, I can find some of these matches even though I
might share 0 centimorgans with one of those people. The
other people did show up. So, test everyone you can. And test
everywhere. Don't limit yourself to just one of these
databases. Test with Ancestry. Test with 23andMe. Test or
upload to Family Tree DNA and MyHeritage and GEDmatch. All
of these databases, like I pointed out, they use different
SNP sets. They use different algorithms. They have different
criteria. And because of that you're going to have different levels
of matches with every single one of them. So if you haven't
tested then this Christmas season actually a great time
because there's going to be sales going on. Get some DNA
kits for your close relatives. Get them tested. And help your
genetic genealogy. If you'd like to learn more about DNA then
watch this video up top. But if you're interested in something
else genealogy related watch this video down below. Be sure
to subscribe hit that like button. And join FHF Extra for
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