So you found your match list on GEDmatch, on the new Genesis system and now you want to
compare your specific kit with somebody else's specific kit. how do you do that? Howdy I’m
Andy with Family history Fanatics and this is a segment of DNA. be sure to subscribe to our
Channel and click on the bell if you want to be notified about upcoming episodes in this
series. I'm going over each of the tools on the new Genesis system by GEDmatch. and today I'm
going to be looking at the one-to-one matching. a one-to-one matching is where you can find detailed
information about a specific match. so let's go over the Genesis system and see how this works.
now once you've logged into the Genesis system there's actually several ways you can get to the
one-to-one matching. I'm going to go through each of them just so you know how. if we scroll down
to the DNA applications we can see that there is the one-to-one autosomal DNA comparison and the
one-to-one X DNA comparison. now these tools are very similar the only real difference is,
is that the X DNA is only looking at one chromosome, the X chromosome while the autosomal
DNA is looking at chromosomes 1 through 22. when I click on it, it's going to get me to the Genesis
one-to-one match screen and you can see what you need is you need to get numbers in order to use
the one-to-one comparison. now these could be to kit numbers that you manage or they could be to
different kit numbers. but there's a couple of other ways that are probably actually easier to
get to the one-to-one match screen with a specific match that you want. now previously I showed you
how you can get to the one-to-many match screen by just clicking on one of the kits that you manage
and when you do that it pulls up this information if you click on any one of the A's in this column
that is going to go to the one-to-one match screen and it's going to have those two kit numbers
already filled out for us. another way to get to the one-to-one is through the one-to-many beta.
and if we click on that we put in our kit number then it will give us our list of matches. and we
can go down and what we want to do is we want to click on either the autosomal number of shared DNA
or on the X DNA that we share with them clicking on either one of those also gets us to the
one-to-one screen. and it already has the two kit numbers filled in. so once we get to this screen
once, we have our two kit numbers filled in, there are several different options of different things
to look at. now the first one is the show whether you want to have the graphics in the position.
just the position or just the graphics. let's take a look at what each one of those shows. so
this first is with graphics and position. and what it does is it goes through each one of
the chromosomes. and there's gonna be a little table here with these segments that you share.
then there'll be a graphic that is displaying what those segments are and that goes through
all 22 chromosomes at the top is the legend of what each one of those colors mean now if I just
wanted those positions I didn't necessarily want the graphics I can click on the position only and
it will give me just this one table that has all of those segments so if you are taking segments
and making your own table of matching segments then this is really what you would do because
then you could easily copy this whole table paste it into your program and be able to have those
matching segments it's also useful if you use DNA painter in that you can copy those segments
and paste that directly into DNA painter to paint your different segments now if you just want the
graphic only then all you're gonna get is each one of those chromosomes in this little graphic
now I use each one of these functions in different ways because sometimes I'm looking at DNA by the
tables sometimes I want to have the computer take those numbers and manipulate them other times I'm
looking at the graphics for a quick visual of how we might be related now that is the basic
information the next option is the builds that you want to display whether you want to display
build 37 36 or 30 now it defaults to build 37 but what this really does is it just changes what the
position is for a lot of these things so each one of these builds uses a little bit different
example and so the numbers are slightly different so you can see in this first one this goes from
fourteen point seven million to twenty four point two million whereas in build 37 its fourteen point
eight to twenty four point four and in build 38 it's fourteen point five to twenty 4.0 so
a little bit different numbers because they use a different reference set for determining what those
numbers are overall the amount of centimorgans is going to be the same and the amount of snips
is going to be the same now normally I just leave this at the default of build number 37 but if you
do work with other kits from other companies that may use one of the other builds then this
is useful for actually being able to compare what segments from a build 37 kit is matches up with
what segments from a build 36 or a build 38 kit the next option here is the window resolution
and this tells you how big you want that graphic to be now it defaults at 1000 which is a thousand
pixels wide and so let's just take a look at the graphics and on this screen here you can see that
a thousand pixels wide takes up almost the whole screen not completely but almost the whole screen
if I go back and I change that down to 750 well now my bars are all shorter they only take up
three-quarters of the screen so depending on how big your screen is if the default is beyond what
you have then you can shrink that you can also make that larger and in this case you can see
yeah now it's much larger I have to scroll to be able to see where all of those segments are on the
graphics part the other thing is if you're really interested in having a single pixel length for
each snip you can click on this full resolution now there's some times when this is really useful
when you're trying to pinpoint a specific location on the genome what is different about this is that
this actually has another graphic right underneath it this white one which tells you the position so
for instance 10 M is going to be 10 million 10 mega bases 20 mega bases 30 mega bases 40 mega
bases and on now each one of these little tic lines whether it's red yellow or green represents
one snip and whether or not that snip is matching between those two people but you can see that if
you do the full resolution you are gonna get a very very big long graphic and it's all dependent
on the number of snips so you can see that some of these chromosomes have much more snips in them
than others and so they're much longer as we go down to our smaller chromosomes there's not near
as many snips and so they end a lot sooner but again if you need to figure out exactly where
a certain part is then this might be useful for you I really don't use the full resolution a lot
I usually stick with just the 1000 so next we're going to get into the snip threshold size now what
it is to call a match is there's two things that are needed and that's what these next two are is
the snip threshold and the centimorgan threshold now for a segment to be called a match it has
to match both of these and so the first one is is it has to have between 200 and 400 snips in a row
that match and then it has to have at least seven centimorgans in size match and so that's what the
defaults are and you can change that if you would like so let me just take a look real quick here
because I want to see something that I can change that you'll see a definite change alright so here
on chromosome number two I have a segment that is only seven point nine centimeters long and it
is eight hundred and thirty-four snips long and so it's calling it a match because both of those
are above seven centimorgans and above that two to four hundred snips so what if I change this snip
limit to nine hundred well now when I go down here I can see that that segment on chromosome
number two is gone because it doesn't meet my snip limit it's still seven point nine sentence
but it doesn't meet my snip limit the same thing if I take away that snip limit and I put in let's
say $0.10 Americans when I go down that segment is still gone on chromosome number two because
it doesn't meet that 10 cent a Morgan snip limit that I have so where would you want to use these
well there's a couple of cases you would want to use this first off if you have endogamy in your
family meaning that you have lots of relatives that might have been third or fourth or fifth
cousins that just intermarried over a long period of time meaning you share a lot of the same DNA
and that means a lot of these segments might be just common throughout the entire population in
that case you might want to change your segment size from 7 to 10 or even 15 in which case now
it's going to eliminate any segments that are smaller than that so hopefully what's left is just
gonna be the ones for those more closely related about 3 divides you the other time that you might
want to change the snip window is if you have kits that don't share a lot of snips so if you
watch that one too mini video there was some kits with overlap that only had about 50,000 snips now
Genesis for the most part has adjusted for this but what we can find is that if we put a smaller
snip limit in and if we put a smaller segment size limit in we're gonna find more segments
the more likely it is when we share a lot of snips then these segments are probably more just false
matches or matches just because we're from the same general population so let me show you I'm
gonna actually change this snip threshold to 100 and I'm going to drop my minimum segment size down
to 4 now you can see already on chromosome number 1 there's this 5 right at the beginning of that
chromosome that was only 171 snips so it falls below what that centimorgan threshold is and you
can see here's some other ones that are below that and so it's finding some of these other segments
that are much smaller so if you're going to use the snip threshold size make sure you understand
what it is useful for again if you have a kit that you don't share a lot of segments with then it's
useful to change that snip size down to a lower level to hopefully find some more segments but
if you've already share a lot of snips if you're over a hundred thousand then it's probably not
gonna be very useful because it's gonna find a lot of little segments that aren't really
matches so this next one is called the mismatch bunching and this is actually related to the snip
size it defaults by taking that snip size and dividing it by two let me show you what I mean
by these mismatch bunching so when the computer is looking at a match it is looking to see that
it has at least a half a match continuously for that time but it allows for some mismatching you
can see in this match right here I have a half match over this 24 to 72 megabases section of
chromosome number 3 it's 51 centimorgans long and it looks like there's one little red mark right in
the middle there but it's not been divided up into two segments what that means is that the
computer is going to look for the first mismatch and the first mismatch it's gonna basically create
a marker after that mismatch it's going to look to see how close the second mismatch is and you
can see in this case it's not till the end here that that second mismatch is if that mismatch
is closer than half of the snipped limit the snip threshold that was that 200 to 400 then it's going
to cut it off and say that hey it's no longer a match and so in this case there probably was not
another one in the right range and that's why it kept all the way through and you can see that as
you go down there's lots of different segments that might have one solitary one or sometimes
even two solitaire ones here on chromosome number 13 you can see a good example of where it found
a first mismatch and then shortly thereafter it found a second mismatch and there likely was not
you know that 100-200 snips in between those two and so it actually calls that a little no match
in that area now if you change that bunching limit it's going to change whether or not it calls this
a no match so let's see if we can actually change the values so that it is not a no match in that
area but it's actually a match so in order to do this what I'm gonna do is I'm going to define my
snip threshold I'm gonna put my snip threshold at 500 and I'm going to make my bunching limit at 100
let's go down to chromosome number 13 and we see hey at those levels it is still a mismatch let's
try to change that down to 50 now and they're at 50 as a bunching limit you can see those two red
marks still show up but it's no longer called a no match in that section so now this is calling the
entire thing one great big section now why do these mismatches happen sometimes those
mismatches happen just in processing the DNA and so they may be they may be errors where actually
is called incorrectly sometimes it's just because those are close together and there was different
recombinations right in the same area and so those really are multiple segments now that's something
that when you get more knowledgeable about how to analyze DNA that you may use these bunching
limits and the snip window for probably most of your analysis you're not going to use those now
the next one is to show fully matched segments and this is those areas where you fully match people
so you really only want to use this when you know that you have siblings or double first cousins or
something else where there is going to be fully masked region because if I click on it right now
this is with me and my aunt you'll notice that there's really no areas that we fully match which
is expected because she's only related to me on one side of my family but if I come back and I
do this same thing now with my mom and her sister then it's going to highlight those areas that are
fully matched areas and so I can see hey what sections are fully matched now they also will
have half matches on some other areas but this gives me the fully matched segments now if you
are doing some visual phasing then this is a great tool to quickly be able to grab those numbers as
far as where that fully matched region is now the last one is this prevent hard breaks and this one
might be a little bit difficult to understand but it says that it's default is to create a
hard break when the distance between snips exceeds 500,000 base positions remember on your genome the
companies have analyzed about 700,000 positions some of these are more evenly spread out in some
cases they're actually really far apart between one snip and the very next snip and so what
Genesis defaults to do is to create a hard break so let me show you what this might mean as we're
looking right here on chromosome number one we can see that hey there is this segment right here
that then it looks like there's a part of it where it is a no match and most likely this is because
this has created a hard break there's a snip and then there's about 500,000 bases before the next
snip and so it's going to default and say well there's a break there because it really doesn't
know whether or not it's a match in that area on the other hand we can see overall with this green
the whole section before and after is a fully matched section and so it's really likely that
that is fully matched in that section as well if we go back and we click on this so that we prevent
hard breaks so it doesn't automatically put those in we can see on chromosome number 1 it has not
broke that segment it has maintained that now as all one segment and this is something that I do on
almost every one of the searches on Jed match is I don't prevent those hard breaks so when you're
doing a one to one comparison one of the things I highly recommend is you actually go and change
this so that this box is checked so that is how you can use the one-to-one match comparison and it
is a tool that you should actually use on all of your matches before you contact them because the
one-to-many match is just a gross overall look at it you want to do the one-to-one comparison
to make sure that you actually match on some segments of DNA and hopefully that segment is
significant enough and maybe you actually match some other family members on that same segment
that you can be able to provide this match some information for now if you have any questions
about how to use the one-to-one comparison put it in the comments below and I'll try to answer it
remember that X comparison is operates the exact same way it's just comparing the X chromosome.
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